Damp - General Queries

How much should a damp course cost?

How much should it cost?

We are frequently is asked is 'How much should it cost' to carry out different types of remedial treatment in a property. Experience has shown that there are regional variations but we also know that there are sometimes enormous differences between companies quoting for the same work. It is important in these circumstances to very carefully compare who is quoting for what and who is omitting some aspects of the work that others may be including. If you go to the articles section of this site and read Articles 4a - 4d inclusive we hope you will be better informed.

Larger organisations obviously have greater overheads than a sole trader and logically one would think this should influence prices but it is not always the case. So what is a reasonable price?

The price a contractor charges is usually made up of two elements: 1) The labour charge which normally includes all overheads etc. and 2) costs specific to the job such as materials, plant hire, rubbish clearance etc. Outlined below are three different trading styles for three different types of contractor:


1. The organised sole trader

Let us look at a sole trader who rents a small yard employing a labourer and his wife on a part time basis. He wants to earn £30K per annum, his labourer £17K and his wife £10K. If we now factor in all overhead costs associated with running such a business over a twelve month period a figure in the region of £85K would need to be generated for this type of business just to stand still.

If we now deduct holidays, bank holidays, illness provision etc this leaves our organised sole trader 44 working weeks to generate £85K. Divide £85K by 44 weeks and he needs to earn £1931 per week. Divide this number by 5 and he needs to earn £386 per day. It is important to remember however that this is just the 'labour only' element of the job. The cost of materials, rubbish clearance, plant hire etc. specific to the job would be in addition to this figure.


2. The less organised sole trader

If we now look at a contractor who works on his own form home with no yard, wanting to earn £25K per annum, cutting back on certain overheads and targeting to work 46 weeks in a year. He would need to generate somewhere in the region of £35K per annum in labour costs to achieve this. On this basis a day rate of £152 would be necessary plus materials.


3. The small organised company with four vans

Finally if we now look at a small organised company with a director/surveyor, one other surveyor, 2 office staff, five operatives and four vans. This company would need to generate £365K per annum in labour costs. However because the company has four working vans the day rate requirement would be somewhere in the region of £400 - surprisingly not too dissimilar to the organised sole trader in 1 above.


Timber preservatives and rising damp treatment fluids and creams are relatively speaking not very expensive. Cellar conversion work using membranes, sumps and pumps does have higher material cost content. To gain an approximate idea of how much a job might cost therefore depends how many man/van days the job will take plus materials. There is no industry set price per meter run of wall or square meter of surface to be treated.



Trying to get a feel of the price for DPC work

Q We have bought a 3 bedroom terrace which is being renovated. It was built in 1905 and was constructed without a DPC. We recently obtained a quoted on chemical injection damp course from a local contractor and he quoted £2,850 for the work. Bearing in mind that this was just for the injection and the backing render (not skimming) as we still have to apply plaster to rest of wall. Also we have done all the labouring and there is no Plaster on any of the walls. Does this seem high? Just trying to get a feel.

A All residential properties built after 1875 should have an original DPC but some don't. Difficult for us to comment on prices as there are many factors that go towards making a price. There are a few questions about prices on this site already.

If we imagine a new DPC were to be injected into all walls using a modern cream type DPC material (Dryzone in our opinion is the best - there are less expensive 'look alike' versions available) one man could easily treat your house in one day. If the walls are all already hacked off by you and are going to be rendered only by the contractor up to 1.0m (following a DPC requires two render coats) we would expect a plasterer and labourer to do this whole job in 2/3 days. Obviously we have not seen the property but £2850 does sound on the high side.


Flood damage or rising damp?

Q 6 months ago I moved into a 1920's semi. Since moving in I have found out that a year or 2 ago there was a leak from the bathroom and the whole downstairs flooded while the owner was on holiday for 2 weeks.  I have started to notice damp patches on the wall behind the kick boards in my kitchen but can not tell how bad the damp is behind the units. How can I tell if this is rising damp or water from the flood? Since the flood the hole downstairs has been replastered, new floor and new kitchen fitted.  I am told that the house was first built with a quarry tile floor.  I think at some point there has been work to the damp proof as on the outside walls there are holes drilled and filled holes in the brick about 9" off the ground level.  I would be grateful of any help.

A Damp originating from the ground (rising damp) contains chloride and nitrate salts. It is possible to analyse samples of the damp plaster to look for these salts. If no salts are found then rising damp is unlikely and it could therefore be related to the flood. If salts are found then rising damp is or has been present. Rising damp is common in kitchen's of 1920's properties where the kitchen floor is of solid construction. This is because the solid floor bridges the original DPC. You should investigate further to see if you have a guarantee for any damp treatment. This should have come to light when you purchased the property. I  would suggest that you have an independent survey undertaken for an unbiased opinion.


We think the patio caused the damp

Q We live in a Victorian house. We have damp in the kitchen and back room and we think the damp is due to a concrete patio all around the back of the house. So to fix the problem we had french drains, acco drains fitted around the house and removed the patio replacing it with gravel and slabs to let the water disperse. Do we need to damp proof the walls or just remove the plaster and let them dry out before re-plastering?

A You said that you 'think' the problem was due to a concrete patio. Do you know this for certain? During the excavation was the original DPC exposed - if so what type is it? Are there any solid floors inside which are original and above the level of the original DPC? As to whether or not the walls will dry out - only time will tell and then only if your diagnosis and remedial works were correct and adequate. One thing that is certain is if the walls were affected by ground water for a period of time then hygroscopic salt contamination of the plaster is very likely. This will disguise any drying that might be happening and the only way to prevent it is to remove the contaminated plaster and replace it with a salt retardant render and skim finish - not just any old plaster. A damp wall could take years to dry down so do not expect an instant fix.


Damp around extractor

Q I have a dark mould growing on my wall which seems to be spreading to the ceiling causing the paint to peel. It is mostly concentrated around the cooker extractor pipe which goes through the wall to the outside. Does this sound like a damp problem? Could the extractor pipe be fitted at a bad angle causing water to creep back in from outside?
Difficult to say without seeing it. It could be fitted at a bad angle (sloping inwards) - have you checked this? Is the outside sealed adequately? How about condensation forming within the flue and running back - this is very possible for a kitchen extractor. Mould will only tend to grow with a pure water source i.e. rainwater or condensation.

Damp kitchen - Loads of questions

Q We have a Victorian semi and have just taken the kitchen out and found in places wet/heavy damp walls and in other places damp walls and some dry. The damp on the worst wall goes up to 6-7ft but is dry in some places below the highest point of dampness. The outside wall is rendered and when we moved in there was no drainpipe to a drain and water was pouring down the wall. Also the previous occupants had built a patio right up to the wall covering the original slate (we assume) damp proof course. We have since added a drainpipe and cut the patio away from the wall and put a trench round the wall so there is a gap now between the wall and patio. What would be our best course of action? Would we need to remove the render off the outside wall and re render after putting a treatment on the bricks underneath? Would tanking be a good idea? Or would a chemical damp proof course be a good idea and how can we get rid of the damp high up the walls? Many thanks in advance.

A So many questions! It is difficult for me to offer specific advice on your problem without seeing it. Can you send photos? Are the walls plastered onto the brick or is dot and dab plasterboard present? Why would you want to take the external render off? Is it cracked and defective? What were you thinking of treating the bricks beneath with and for what reason? Tanking sounds like a sledge hammer to crack a nut. Maybe a DPC and floor to ceiling waterproof render would be adequate (get your first fix electrics in place first though!) but I need more information first.

If the walls are damp due to the missing rain water pipe at high level this can take a long time to dry - many many months. Is it damp at high level where the rain pipe was missing or elsewhere? More information and I may be able to help.


How long for damp to dry in period property?

Q After discovering leaking hot water pipes (both water and central heating) on the ground floor of our newly purchased period property we re-plastered all the damaged walls and replaced the wooden flooring. Not all pipes were replaced which I now think was a mistake. I'm sure we have more leaks. How long does it take for (new and old) wet plaster to dry? I recently purchased a damp meter which reads very high moisture content. The original problem was discovered and fixed some 5 months ago. The floors and walls were very wet at the time. Would you expect the meter reading to be dry now?

A How long new plaster takes to dry will depend upon the type and thickness of plaster applied, the volume, construction and  moisture content of the substrate onto which the plaster was applied and the ventilation of the area in question.
If the substrate is a large mass of relatively porous brickwork which was saturated it will probably take years to fully dry down. Another possibility is that the moisture as a result of the leak has dried but you used a plaster such as Carlite Bonding or Browning which has exacerbated another problem or the consequences of a previous problem, that the original plaster may have been containing i.e. rising damp? What type of plaster did you use? It may be that you used a plaster that was not suitable for the conditions present. Be careful when interpreting the readings of a moisture meter which are very sensitive when used on walls - but useful in the right hands!

Q Many thanks Peter for your response. Sadly I have no idea of the type of plaster used (my plumber plastered the walls for me). The original plaster is also reading very damp but the walls are flaky and dry to touch!  I also have one of those 'salt' lines appeared on the wall - which first highlighted my concern about further leaks. I'm suspicious it may be my novice interpretation of the meter readings. I've asked a local maintenance company to give an opinion today.


Penetrating Damp - Do I need to re-plaster?

Q We have penetrating damp in the living room caused by a gutter problem and a probable breach of the cavity wall. It's about 1 sq foot. We are having the gutter repaired and exterior brickwork repointed and sealed. Do we need to re-plaster? (Our builder says we should) - The wall is wallpapered and looks OK at the moment - though a bit lumpy. I'd prefer to just leave well alone and see if the gutter repairs solve the problem.

A If the source of dampness was as you state rainwater, this contains no salt contaminants thus there is no reason  to change the wall plaster (due to salt contamination) unless its adherence to the underlying brickwork has been affected. The "lumpy" effect may be the result of sulphates forming at or near the surface of the underlying plaster as the water evaporates off.  Sulphates are naturally present in most building materials and this is not unusual in moisture penetration situations. This lumpiness will not disappear or go away on its own so as and when you redecorate at some time in the future you will probably have to re-skim the wall plaster in this area prior to decorating or at the very least fill and sand smooth.

It would be necessary to change wall plaster if salt contamination was present. This occurs when the source of water was from the ground and in these circumstances the plaster would probably contain chlorides and nitrates which would have to be removed since they are hygroscopic (moisture attracting). I would suggest therefore that you wait and see what happens to the damp affected plaster prior to undertaking any renewal.


Penetrating damp - How long for walls to dry?

Q I have a 1st floor flat about 100 years old with very thick stone walls. I have had a problem with water penetration on two walls and have had some remedial work done but I don't know how long to wait for the walls to dry out before having more work done. I was told the problem could be from the roof, the walls or the chimney stack or all 3. How long can I expect my walls to take to dry out? They are about half a metre thick and I'm sure the weather this summer isn't helping the process.

A How long a wall takes to dry depends upon how wet it is and the ease by which moisture evaporation can take place from it. Thicker walls will take longer due to the surface area to volume ratio. Very wet walls could take many many months to dry fully some even years. If the dampness is chimney related then contaminant hygroscopic (moisture attracting) salts may be present and the wall will give the appearance of never drying even though the problem has been cured. I am perplexed as a good competent builder should be able to pin point the problem and fix it. Why is there doubt?


Damp boards - No reason?

Q I have recently moved into a 1900s house in Beckenham Kent. When the air is damp, some of the floorboards in our hall often become damp along the edges. This does not affect any other boards in the house. Several months ago, a builder had a look under the boards and stated that he couldn't see any problem. However, this problem has continued and I'm now becoming concerned that we may have a major problem.

A If your builder could not identify any problem beneath the floor - such as no obvious damp and the sub floor ventilation is good then it sounds like there could be some form of hygroscopic (moisture attracting) contamination - perhaps a previous owners pets? Try scrubbing the edge of one of the affected boards with plain water and soak it as dry as possible with kitchen towel. This should remove some of the contamination if it is present. When it happens again compare the scrubbed board with the others. If the scrubbed one is better then you have your answer.



Boards nailed to concrete causing damp?

Q I have obtained a house with floorboards nailed directly to a concrete floor in 2 rooms. Only these rooms show signs of damp. Is it because the damp is tracking up the nails? The boards are damp and the walls beginning to mildew. Thank you for your help.

A I note what you say with regard to the floorboards but it is likely that these are nailed to timber fillets embedded in the concrete beneath the floor.  This type of construction does leave the floors susceptible to wet rot decay, but if it is an older property and the floors are original then there is probably no reason why this should suddenly occur. I do not understand what you mean by damp tracking up the nails, but the nails may be corroding if the timber is of increased moisture content. If the walls are beginning to show mould growth then this is likely to be the result of condensation or rainwater penetration and not rising damp since mould does not grow where rising damp is present. From the information provided there is little more I am able to say.


Rising Damp - Could boards and joists be damaged as well?

Q We are in the process of buying a new house. The survey results show rising damp. The repair costs are £1500 to re-plaster and inject damp proof course.  The report is only a visual one. Is it possible the floor boards and joists could be damaged?
A Any company that has made a diagnosis of rising damp has a duty of care to inform you that timber adjacent to the damp affected walls is at risk to fungal decay and should be inspected. If they have not done this then they have failed in their duty (and failed to conduct a survey in accordance with BS 6576).  Well done for thinking about it and make certain you get it checked out before you proceed.


Water under my floor

Q I own a semi-detached house built around the 1930s.  A few weeks ago I discovered that there was a small damp patch just above the skirting board in the lounge - the wall paper had begun to peel away and some salty deposit on the plaster. The wall in question is an internal load-bearing wall dividing the lounge and the kitchen.  The kitchen has a concrete floor. The lounge has a suspended wooden floor - underneath the floorboards there is a void of about 75cm with concrete at the bottom (top of the soil). I removed some floor boards near the damp patch and on inspection saw water present (2cm depth) just around that area. I suspect this water is rising up the wall and causing the damp. There is no evidence of dampness on the other side of the wall (i.e. in the kitchen). Where has this water come form? I thought that it may be the water mains leaking so I arranged for the water supply to be turned off from the stop cock on the pavement out site. It is now over 4 weeks since the water has been turned off, but the water under the floor boards is still present. Could this water come from a neighbouring property with a leaky water mains? A friend has advised that it may be spring or ground water that is causing the problem. How can spring or ground water be 'diverted' or moved away from under the property (e.g. by putting sand or something on the concrete)? What is the best remedy and the cost involved?
A A 1930s property will have a damp proof course (DPC) in the walls and provided is being allowed to work correctly you could have a river beneath your property but damp should not rise past the DPC. Indeed I have surveyed numerous properties one of which had a stream beneath the floor and others with water depths of between 10cm - 30cm subject to the varying height of the water table. So it is not unusual to have water beneath a property. It is essential however that the sub floor ventilation is very good indeed - 9"x6" efficient air bricks every 1.5m in all external walls. By efficient we mean square pattern metal or plastic louver type but NOT terra cotta type as these are only 20% efficient and have the ability to bridge a DPC

You are correct to investigate all other possible ways by which the water may have entered the property and no doubt you have checked the plumbing on the kitchen side of the wall. One point however, in 1930s properties the DPC was built in at a level to protect the timber floors - about 8" beneath the timber floor level but when they in filled to create the solid floor for the kitchen they often bridged this DPC so it is not unusual to have damp in the walls surrounding a solid floor in such a property irrespective of the water under the floor.

Your local water authority is able to test the water to see if it has come from a main because it contains their treatment chemicals - chlorine, fluoride etc. so perhaps this is worth a try. If you put sand on the oversite the water would still be there in the sand but it would just be out of sight. If everything draws a blank your friend could be right but do not worry - just make sure it is well ventilated


I'm thinking of buying a basement flat

Q I am thinking of buying a basement flat. Do they necessarily have dampness as they are below ground level?  The flat smells of damp, what can be done about it, is it costly?

A Basement flats are very susceptible to rising damp, penetrating damp and down damp and often when a problem has presented itself in the past, due to a lack of knowledge and understanding, it was bodged up. To deal with dampness in a basement correctly can be very costly indeed. Basement flats are also known to suffer from condensation especially during the cooler winter months - this is almost certainly what you smell - mould as a result of condensation. Dampness does not smell - it is the mould associated with condensation that you smell. Perhaps this is why it is being sold in the warmer months? Has it been painted very recently - especially the bedroom? Perhaps to cover the mould patches?
My advice would be to be very very careful if considering a basement flat.

Q Thanks for your help and yes it had been recently painted


Will moving in reduce the damp?

Q We are currently buying a 100 year old terraced house that has been empty for several months. The basic survey stated there were high levels of damp. A damp company quoted for injection of DPC and re-plastering. I am concerned about getting this needlessly done, as I believe the problem may reduce when the property is aired properly as the owners said they had no problems when living there. Is this likely to be the case? The property is newly decorated so there are no obvious signs.

A Any wall in a house, be it empty or occupied, should not record the presence of any increased moisture presence on a surface moisture meter. If your surveyor found damp and a damp treatment company has quoted for remedial work then it is very likely that there is a damp problem of some sort. Moving in and living there is unlikely to reduce this - in fact it may make the problem more apparent.
I would expect a vendor to say they did not have a problem since they are trying to sell the property. I would also be very suspicious if it has recently been decorated especially if damp has now been discovered. If you like the property get several quotes to correct the damp and reduce your offer accordingly. Remember you will probably have to sell the property one day and if you do nothing now it will cost you in the long run.
Sorry to be so forthright but buying and selling property is not always a pleasant business so beware. Good luck


New window - Now more damp?

Q We have just had fitted a new uPVC bay window. We previously had wood windows, and damp patches on either side of the bay, about 3 feet off the floor, but when the old wood bay was removed, there was no damp evident at all on the wood, or the frame areas. The damp is now worse with the new window. The old roof of the bay is the same, but I have been told by the window installer that it looks fine, and did not need to be replaced. The damp is not growing mould, but is damp to the touch. There is a damp proof course, with a 25 year guarantee.

A The new windows are almost certainly more draught proof than the old wooden ones and as a consequence water vapour generated in the property is taking longer to dissipate to the outside meaning that the vapour pressure inside the property is greater than it was previously.

The damp proof course work probably hacked off and renewed plaster up to a height of three feet from the floor and the damp patches you are now seeing are likely to be just above where the new plaster ends. The highest part of rising damp is referred to as the salt band because it contains the highest concentration of chloride and nitrate salts which are brought up from the ground. These salts are extremely hygroscopic (moisture attracting) and will cause damp patches to occur on a wall especially during damp or humid conditions.

To conclude therefore it is possible that the damp proof course company did not hack off the plaster high enough resulting in the 'salt band' creeping above the height of the new plaster. Now that vapour pressure has increased in the property (new windows) the hygroscopic action of the salt contaminated plaster is now more apparent. Does this sound feasible? If so get the damp company back as they should have taken the wall plaster to the correct height to begin with. The wood of the frame is unlikely to be affected by salt contamination and thus would be dry. Let me know if my theory works

Damp stone house - buying unseen!

Q Hello. I am looking at buying a small stone barn that has been renovated into a little studio. Problem being I have to buy sight unseen due to the fact I live in Australia. I have a very good agent however; she has just mentioned to me that the previous people viewing the property noticed a damp spot on an internal wall downstairs about 70cm. She mentioned that leaving a small radiator on over winter may rectify the problem or we may need to have a damp treatment. Should we go ahead and buy, we were told its common in this area and because the house is so old. It also has recently been restored.

A You are very brave to buy sight unseen! Is the agent working for the vendor or are you paying her? You should certainly commission a survey of the property, perhaps a house buyers report at the very least. This is common practice over here and necessary to protect you. Be wary of 'recently restored' especially if it was a property speculator as every extra penny they spend comes out of their profit thus they can cut corners. The age of the property is irrelevant - it should not have any damp showing - end of story! Instruct a surveyor to inspect the property!

Damp just above skirting

Q I have damp rising to approx 3"- 4" above the skirting board on an internal wall that joins an external wall. Is this rising damp? It's been there a while and hasn't risen up the wall to the height described for rising damp. On the outside, at the point where the internal wall joins the external wall is the drain. Is this a possible cause?

A There is no defined height for rising damp so what you describe could well be rising damp but it is what has or is causing it that needs to be established and I would need to know more details before being able to help. How old is the property? Has any previous DPC work taken place on this wall? Construction type? Any history of floods, washing machine leak etc? Did it suddenly appear? Is only one wall affected? How tall is the skirting? Is the skirting decayed? Are any other walls affected? Whilst the actual drain outside cannot be ruled out it is unlikely to be responsible since it is almost certainly below damp proof course level.


Do I drill Staffordshire blue bricks?

Q A question regarding the correct location for the administering of a chemical DPC. If I have an existing DPC of Staffordshire blues - where would I inject? Into the blues? Below the blues? Into the mortar joints or above the blues? I know it will take a time to drill the blues, as well as several drill bits but what is the best option? Thanks in advance.
A Staffordshire Blues (bricks) are a form of damp proof course in their own right and these do not break down. If a wall containing such a damp course is suffering from rising damp then the only path available for the moisture to rise is via the mortar. Attempting to inject such bricks would be a waste of time due to their exceptionally low permeability and they would not be responsible for any rising damp. In these circumstances the mortar joint should be targeted and this point is made in BS 6576. Of course you need to be certain that you have rising damp in such walls before you do anything. Good luck and I hope I have saved you a few drill bits!


Spreading greasy damp

Q I have recently moved in to a stone built Victorian mid terraced house. We have now noticed that there is a damp patch on the internal wall between our house and next door. It started off small but has spread all along the inside wall across to the chimney it feels almost greasy. Next door the render is cracked and is in need of some repair. Is this likely to be where the damp is coming from? If so are they liable for any repairs that need to be done?

A From what you describe I assume that you mean the party wall with next door which would therefore be inside the property. If this is the case I do not understand how cracked plaster next door could cause damp? (unless I have misunderstood and it is an outside wall). How high up from the floor is the damp patch(s)? If it is approximately one metre then it could have crept up behind a waterproof render previously applied to the wall and is now showing above it. The 'greasy' feel could be a high concentration of hygroscopic salts. These can sometimes be tasted with the tongue if you dare! Is there a guarantee for damp treatment on the property?


Is £4000 too much?

Q I have just had an independent damp company give me a quote on treating rising damp that has been found at my property. They have told me it will cost £4000 (2009 question) to treat which seems quite expensive. The damp has been found in about 25 metres of 9" wall.

A You state that you have had 'an independent damp company' give you a quote. I am not sure what you mean by 'independent'? It sounds like this company is a commercially trading contractor with a vested interest in their own diagnosis otherwise they would not have quoted you a figure. Without seeing the potential job it is impossible for me to comment but if you scan my questions and answers in all sections there is guidance on 'how much does it cost'. Make sure you obtain three or four quotes before making up your mind. As an alternative you may wish to consider engaging the services of a truly independent surveyor such as myself who has no financial interest in any work that may be necessary thus it could save you money.


Cellar - Damp Course - Dehumidifier

Q I have just recently moved into a 1900 Victorian Terrace. I don't know where to begin with the cellar as some of the walls are a bit damp. I am only going to use it as a games room. I had a damp course done 6 months ago. The walls where it got replastered looks like they have dried out but have bits of crystal on them, what does this mean? Also the old paint that was already on the walls is starting to bubble and flake off, again. I'm not sure what this means? I will be buying a dehumidifier but not sure what type size I should get. I eventually want to repaint all the walls but not sure what procedure I should be doing! I would appreciate any advice you can give me. Thanks

A By cellar I understand this to mean an area under the house, usually with earth retaining walls. As a consequence to provide dry wall surfaces it is necessary to either tank or dry line the walls from floor to ceiling which should be linked to a waterproofed floor. A remedial DPC in a cellar situation is seldom of much benefit. The white crystalline deposits on the surface of new plaster are probably sulphates which are present in most building materials, especially finish plaster. They usually form as the new plaster dries and may be brushed off. If they keep appearing it means water is continually evaporating and greater investigation is needed. Old paint bubbling off walls in a cellar is usual as the walls are probably damp. A DPC injection will not stop this happening. A dehumidifier will do little other than remove moisture from the atmosphere and the amount will depend upon the temperature - it will not suck moisture out from the walls of have any significant effect upon drying them. Do not buy one if this was your intention.

Have you had a chemical DPC injected in your cellar and does it have earth retaining walls? Let us know.


What is the difference between a dampcourse and tanking?

Q What is the difference between laying a damp coursing and tanking a house?
A A damp proof course is a continuous horizontal impervious barrier through the full thickness of a wall that prevents the movement of moisture.
Tanking is a term used to describe the application of a waterproof material onto the surface of a wall to prevent moisture penetration either into the wall (positive side) or from damaging the decorative surface (negative side) - usually in a below ground situations.

Does this sound right?

Q I have just had a damp & timber survey carried out by an 'independent surveyor' on an 1880 semi-detached house. He has said that there are high levels of damp on all external walls on the ground floor using a electronic moisture meter. He recommends using Dryzone and re-plastering at a cost of £5,600 for the work. The walls are solid 9 inch - this seems an awful lot of money. The walls to treat total about 20 metres. Does this sound right? I am a first time buyer.

A No it does not sound right!!

You say the surveyor was independent yet he gave you a price? A truly independent surveyor would not be in a position to do this but he could perhaps offer a guide. Was this the case? Please explain what you mean by 'independent surveyor'.

20 metres of 9 inch thick brickwork will use 6 tubes of Dryzone. Even at an expensive rate of £25 per tube this equates to £150 in product. If we now suppose that your 20 metres of wall equates to 25 square metres of re-plastering. At the price you have been quoted, after deducting the product cost (£150), this equates to a hack off and re-plastering cost of £218 per square metre!! This is outrageously expensive!!

Dryzone to regular contractors usually sells for £10 - £15 per tube so the product cost is more likely to be £60 - £90. I would be very interested to learn more about the 'independent' surveyor who quoted such a huge price. Please send more information or give me a call but DO NOT spend £5600 on 20 metres of 9 inch brickwork!


Basement flat damp concerns

Q I have recently had a survey performed for a house I am buying, well a basement flat to be exact. The building is 120 years old but and has recently been re-decorated by a developer. The survey has highlighted damp within external and some internal walls. Could you advise on our next steps, as looking at the walls there is no signs of any damp and recently (2-3 months ago) they have been re-plastered. The developer is saying there were no signs of damp during redevelopment; however should we still get someone in for an expert's opinion. Thanks in advance for your response.

A My advice when buying a basement/semi basement flat is to be very careful indeed. I would be particularly concerned if the developer has recently 're-decorated'. Experience has shown that basement flats tend to be more prone to the effects of condensation as they tend not to receive the benefit of sun light and the thermal gain from it. Solving damp problems in basement flats also tend to be more complicated hence expensive. Developers are there to make money and the more they spend on a property the less their profit so be careful. We are surprised that there are still timber floors in a basement. Naturally it depends upon a property's situation but many original basement floors have rotted away and have been replaced with solid floors. Is this not the case? Has the developer laid new laminate floors or something else over the original floors? If so why?

If there are no guarantees then you should certainly seek the opinion of damp and timber specialists preferably one that is a member of the Property Care Association . Make certain floor boards are lifted and sub floor timbers are examined. If the developer puts up resistance walk away - it will be cheaper in the long run. Sorry to be a doomer and gloomer.


I think my house has rising damp - my floor is rotten

Q I have three questions if that is OK, as I think my house may have rising damp. Two years ago we decided to fit laminate flooring in a living room. On lifting the carpet we found this had become mouldy and damp, and the floorboard underneath had become rotten, as had the joist below. The plaster was slightly powdery for a couple of inches above the skirting board, but the skirting board seemed unaffected. The area affected was a corner of the room where two outside supporting walls met. As it was two days before Christmas, we did a temporary repair, replacing the joist with an untreated softwood replacement and the floorboards with chip board. This "temporary" repair had been forgotten until this past weekend when I noticed the floor in that corner had too much "give". I lifted the laminate flooring to find the chip board and the new joist was completely rotten and very wet. As well as being wet, the wood was covered in some places by a white rubbery fungus, and over the rest in a black slimy ooze. There seems to be a white powdery dusting on some of the bricks, but again, the plaster above floor doesn't appear to be effected apart from some flaking of emulsion as skirting board level. My questions are;
1. Do I have rising damp?
2. If so, I have read a little on the web concerning Dryzone and the way it is applied. In my particular circumstances, the mortar between the bricks appears very sandy and soft. Will Dryzone still work, or is some form of re-pointing necessary before application.
3. I am in two minds as to whether to attempt the work myself of get someone to do it. My main fear in employing someone else is getting a fair deal. Do you have a list of approved contractors? Thanks

A From what you describe it sounds like your problem is with the floor and not the walls therefore Dryzone would not be relevant.

Prior to laying the laminate floor a small amount of 'ventilation' was happening through the floor itself. Now that you have laid a laminate floor this has been prevented resulting in a humidity build up in the sub floor void and very probably moisture accumulating beneath the laminate on top of the flooring/chipboard. Sub floor ventilation was probably bad originally but this just made it worse. It also sounds like sub floor condensation could be responsible for the paint flaking just above skirting level.

Check the sub floor ventilation. The property should have 9 inch by 6 inch air vents every 1.5 metres in all external walls with an internal suspended timber floor. They should be efficient air bricks such as square pattern aluminium or louvered plastic - NOT terra cotta which are only 20% efficient. Sub floor wall openings should also be present to allow a through draught.

You should get several expert opinions about what exactly is going on and then decide if you want to attempt it yourself. You should use companies who are members of the Property Care Association, formally called the British Wood Preserving Association. Please contact me again if you have any queries or when you receive the reports as I would be interested in learning the outcome.


Do I need to have a new DPC?

Q Not sure if you are the right people to ask but I am in the middle of refurbishing a 40 year old property and I have heard that I need to have the property's damp course done and certified before I can sell. Is this correct? Many thanks.
A You only need to deal with a damp course problem if the property actually has rising damp - There is no formal obligation or requirement for you to do anything. I would not expect a 40 year old property to have a faulty damp proof course so be careful about what people tell you. Hope this puts your mind at rest


Potential damp and woodworm

Q We are in the process of selling our 2nd floor maisonette.  However, our buyer's survey has shown up potential damp and woodworm problems (the property is approx 170 yrs old). The only sign of damp we have is mildew on the ceiling above our shower (which is located downstairs), no tidemarks or furry areas.  These problems were not picked up when we bought the property only 2 years ago. Is this something we should be worried about and would it be costly to fix?

A You state 'potential' damp and woodworm. Potential does not mean it is there - it could be that the surveyor is just covering himself because of the age of the property. Damp in a second floor maisonette would not be rising damp in any event. Is it costly to fix? - How long is a piece of string? Impossible for me to say but if you bought it two years ago and had it surveyed at that time, then it is unlikely that there is a serious problem now if at all.


Will the original slate DPC still be OK?

Q We are in the process of buying a 1930's semi-detached house and learn that the property still has its original slate DPC installed. We have not yet instructed a damp survey to be performed as the house looks, feels, and smells dry throughout. There is no evidence of wallpaper peeling, wet walls (inside or out) or staining and the vendor 'says' they have had no problems. What would you recommend here? Can a slate DPC still be effective, or should we invest in a modern solution?

A There is no reason why the original slate DPC should not be functioning normally. The only potential 'weakness' is any walls surrounding an area with a solid floor - possibly the kitchen. The original DPC would have been put in at a level to protect the timber floors - about 8 inches below timber floor level. When the solid floor was introduced, often in a kitchen, the original DPC was often bridged - sometimes this causes a problem, sometimes not. I assume you are having a survey undertaken (if not you should) so see what the surveyor finds before doing anything.  


Can this damp be fixed?

Q Our cottage has been built with black ash mortar and it has damp around the bottom of the walls. The plaster came away at bits and between the bricks this is crumbling away. Can this be fixed?

A What you describe sounds very typical and yes it can be fixed. Use a contractor who is a member of the Property Care Association.


Damp band at dado rail height but not below?

Q I have bad damp going the full length of the wall that divides my house and the neighbours. The damp is about six inches above and below the dado rail but its OK between the skirting boards and where it starts near the dado rail. What could be causing this?

A Difficult to say without seeing it but one possibility is that a waterproof render has been applied in the past to the lower section of the wall and dampness has risen up behind this and is now showing itself above the height of the render. This is not unusual.


Does rising damp ever dry out?

Q Does rising damp ever dry out by itself or will the area be permanently damp until treated?

A Rising damp will eventually dry out provided the source of moisture has been prevented. However one of the consequences of rising damp which originated from the ground is hygroscopic (moisture attracting) salt contamination. This means that even if the source of moisture has been prevented the wall may still remain damp due to the hygroscopic action of the contaminating salts, subject to the level of contamination present. If the dampness was only present for a short time and rectified, salts are unlikely be a problem and the wall should dry.


What is the best way to dry a wall?

Q What is the best way to dry an inside wall out when you have solved the damp problem out?

A There is no best way other than time. If the inside was kept warmer it would help combined with ventilation. De-humidifiers just dry the atmosphere and therefore only have a marginal effect on the wall so are not really worth it. People tend to think that they 'suck' moisture out of a wall which they do not. Time and patience is the only real way.


Does sewage affect a chemical DPC?

Q Please can you confirm if raw sewage will affect a chemically injected damp proof course together with surface water flooding of a lower ground floor dwelling that will require sterilisation and re-injection of a new chemical damp proof course together with newly tanked rendered plastered walls?

A A correctly installed chemical damp proof course is chemically bound to the masonry into which it has been injected. No flood or raw sewage will reverse this process, remove it, dilute it or wash it away. It is therefore difficult to justify further injection in these circumstances though I am aware many seem to take the opportunity and reinject but in my opinion it is not justified. On what grounds is it being argued that reinjection is necessary? What is the chemistry being applied?
I agree that wall plaster may be contaminated and might have to be renewed and care should be taken that the replastering complies with the specification stipulated by those responsible for the initial injection. It may also be wise to formally inform the company responsible for the initial injection that a flood has taken place and wall plaster is being renewed to their specification - just in case there is a claim situation in the future and they argue that a major event occurred and they were not notified. I would be interested to hear how this progresses.

BS 6576 and all that jazz!

Q We moved into a 17th century stone cottage 4 years ago. Prior to moving in a survey was conducted on behalf of the estate agents, stating that a DPC was required. A report was issued and work carried out according to that report in accordance to BS 6576 (1985). The walls treated were originally exterior walls, but now have an extension attached (pre DPC). The work involved a normal damp proof treatment by drilling holes, and a damp proof course being injected. Due to hygroscopic salts plaster was removed (1 metre) and re-plastered. Recently damp patches have appeared above this plaster line. This does get worse when it rains, but the wall does not have a chimney breast on it and the same wall upstairs does not show problems. The company that did the work insists that as the damp is appearing above their plaster line it is not covered under guarantee 'because they didn't treat that part'. Surely a quote to stop rising damp doesn't mean only up to 1 metre. Should they not have treated the whole wall if that's what they needed to do to prevent rising damp?  Were do we stand?

A Thank you for your question. BS6576 basically states that wall plaster affected by rising damp should be hacked off to a minimum height of 1 metre and a minimum of 300mm past the last detectable sign of dampness. The last detectable dampness is usually located with the aid of a moisture meter. It is therefore not unusual for correctly conducted remedial damp course works to have plaster removed up to varying heights and 1.25m, 1.5m and 1.75m heights are not unusual. Some contractors however are not aware of this and religiously hack off up to 1 metre only. Many contractors make reference to BS6576 in the hope that it will look impressive but many have never even seen a copy let alone read it!

From what you describe it sounds very much like the contractor did not remove the original plaster to a sufficient height i.e. a minimum of 300mm past the last detectable sign of dampness. Another possibility is that the new DPC is not working; the dense render applied in conjunction with the new DPC has concealed the dampness, reduced evaporation previously possible and in so doing driven the dampness higher.

The greatest concentration of hygroscopic (moisture attracting) salts in a rising damp situation is at the top of the rising damp. This is often referred to as the 'salt band'. It sounds very much like the salt band has now crept above the new plaster. The hygroscopic action of the salts explains why the damp is more visible on damp days and less so on dry days.

The bottom line is that the damp problem now evident is almost certainly the responsibility of the damp proofing company. It sounds very much like they did not act with the due care and diligence one would expect of an average specialist damp treatment company. Do not let them fob you off. It is possible however that they do not fully understand what they are doing and what they are now seeing is a whole new experience for them which sometimes create problems due to ignorance. I hope you are able to sort your problem out but if you have any further queries please do not hesitate to contact me.


Damp bathroom - Any ideas?

Q Have dampness to exterior of ground floor bathroom with white salt deposits visible. Unable to see inner walls as they are all tiled. Externally some bricks are spoiled and have lost facings. Evidence of previous damp course treatment. Took out patio blocks from edge of wall and made a soak away. Is the damp likely to be from inadequate damp course or air absorption through spoilt bricks, inadequate pointing etc? Any ideas?

A It is difficult to be specific without actually seeing your problem but from what you describe the cause could be any of the points that you list. The white salt deposits that you are seeing would almost certainly be sulphates which are present in virtually all building materials especially finish plaster which is calcium sulphate. The formation of sulphate crystals on a surface is an indication that moisture evaporation is occurring but where has the moisture come from that is evaporating? In a bathroom it is not beyond the realms of possibility that condensation could be responsible - condensation forms on the render coat beneath the skim coat and in so doing makes the skim coat damp. When the condensation evaporates it brings to the surface in solution sulphates which crystallise as the water evaporates off hence the formation of the 'salt deposits'.

The rectification of damp problems is often a process of elimination. You have identified some potential causes so deal with them one at a time and see if it makes a difference. You mentioned evidence of previous DPC work so why not get the company back for their opinion? See if the problem reduces or even stops during the warmer summer months which would point towards condensation being the problem.


Rising damp in a party wall

Q My daughter is considering buying a mid-terraced house about 100 years old. The dividing wall between this house and the neighbouring house has rising damp. If my daughter has the DPC reinstated to this wall what would be the effect to the neighbour's side of the wall. In cases like this do both parties have to tackle the problem jointly to correct the damp? Also is there a rough guide to the price per metre for replacing the DPC and re-plastering the damaged wall. I would be grateful for any advice on this problem. Thank you.
A Rising damp on a party (dividing) wall is a relatively common occurrence. If there is evidence of rising damp on the side of the wall within the property your daughter is considering buying then it will almost certainly be present on the adjoining side of the wall. It is possible however that the owners of the adjoining property may have already carried out remedial treatment and that what is now evident on your daughter's side of the wall is damage as a result of the original rising damp.

It is possible to install a chemical DPC from one side of a wall and for this to be effective it obviously has to go through the entire thickness of the wall. Work on a party wall has to comply with the requirements of the Party Wall Act and your daughter would be responsible for this. If the party wall in question has "back-to-back" fireplaces with the adjoining property then this does create treatment problems that many contractors do not fully appreciate. Because of the Party Wall Act and also because of difficulties caused by back-to-back fireplaces, many contractors are using "plaster membrane" on party walls. This is a dimpled plastic sheet material with a mesh fixed to the surface to provide a key for new plaster. It is fixed to a wall up to a height of approximately 1.5 metres (subject to the height of any rising damp) and plastered over. This is a very effective long term measure of "concealing" any dampness that might be present.

With regard to a rough guide price, I am not in a position to offer this since there would appear to be huge variations across the country. I suggest that you obtain at least three estimates from contractors who are members of the Property Care Association (PCA) formerly BWPDA - British Wood Preserving and Damp-proofing Association.


Sounds like the vendor did damp treatment on the cheap

Q We moved in to a Victorian house (1895) 9 months ago, and before moving in the home buyers survey raised an issue with rising damp. Before buying we had the seller complete the work as recommended by the approved company, which was an injected damp course approximately 2 bricks above the outside ground level. However something that we did not think of is that the inside of the house is actually 12-18 inches below the ground level outside. Now that we have re-decorated and re-plastered inside, we are seeing sign of rising damp, measuring up to 50% H20 content. I have telephoned the company that carried out the DPC repair, who are saying it is our fault for not using them to re-plaster with the specialist plaster, and it is basically not their problem.
My questions are:-
1. Has anyone come across this before? Particularly the house being lower inside than the new damp course put out side. Should this not have been spotted and a different treatment given?
2. The damp proof company said they would have told the previous owner to use a specialist plaster. However this information was not passed to me. Where do I stand legally?
We have a 20 year Warranty from the company that carried out the work.

A From what I understand your survey highlighted a rising damp problem and the vendor had a new damp-proof course installed prior to the completion of your purchase. From what you state it would appear that they had this carried out as cheaply as possible, i.e. injection of the damp-proof course only, and that no re-plastering works were undertaken.

The company that injected the damp-proof course have a duty of care to their client to point out the consequences of rising damp, i.e. hygroscopic salt contamination of wall plaster, and, if as you state, the external ground level is 12-18" above internal floor level then this should also have been pointed out, the problems it can cause and appropriate recommendations made.

The bottom line is what did the report issued by the contractor responsible for the damp course injection state with regard to the need for re-plastering and the raised external ground level? You state that the damp-proof company said they "would have told the previous owner to use a specialist plaster", the implication being that they may not have produced a report? They should have produced a report pointing all problems out, the consequences of them and other specialist attendant requirements such as re-plastering specifications etc. If they did not you may wish to consider pursuing them. You should study the warranty in your possession as it may state that in the event of a claim you would be required to produce the report to which the guarantee relates, which is normal practice. If your solicitor completed the purchase on your behalf without securing all of the essential paperwork to substantiate a claim then perhaps you may wish to discuss this with him and ask him what he is prepared to do about it.

With regard to practical issues what plaster did you use to plaster the inside walls? The problem that you describe is very common and relatively easy to deal with so do not despair but disruption is inevitable.



Damp in party wall in stepped terrace house

Q Hi, I have recently moved into a Victorian terraced house as a first time buyer and have discovered damp along a boundary wall that I share with my neighbours. The damp proof specialists that I have asked to quote me for the work have told me that the problem is arising because I live in a stepped terrace, and so my neighbour's property is higher than my own. I am therefore getting penetrating damp into the property. They have advocated tanking the walls up to 1m all along the affected wall (which is no more than 20m in total) and injecting the walls with a vertical damp proof course. Does this sound like a suitable course of action? Also, they are going to be charging me around £1500 for the entire jobs - including plastering etc. Does this seem like a lot? Obviously, as a first time buyer it seems like a lot to me, but I really have no way of gauging whether this treatment is the right one or if I am being overcharged. Any help at all would be appreciated.

A Stepped terraced properties do create problems but the extent of these are dependent upon the gradient  of the hill that necessitated the stepped construction when they were built. For example, on a very steep site every property is stepped but on a less steep site the properties may be stepped in twos or threes. The extent of work necessary would be dictated by the gradient. If at all possible you should try to gain access into the adjoining property on the higher side and if the properties have timber floors it would be ideal if one of these could be raised in order to check the height of the oversite (sub-floor soil) in relation to the floor level in your property. Sometimes the original builders were aware of the potential problem and removed sub-floor soil from against the party wall so that it did not cause a problem. If on the other hand the floor in your property is of solid construction and the floor in the adjoining property is also of solid construction then you know exactly where you are with regard to the heights, etc.

From what you describe it sounds like what the contractor is proposing is along the right lines. The height up to which the plasterwork should be removed on your side of the party wall should be a minimum of 1 metre above the height of the raised ground/floor that is present in the adjacent property. It is also suggested that the tanking should be carried out to this height as there is no point in changing specification part way up.

With regard to a damp course injection it is essential that this takes place above the height of the raised ground on the adjoining side of the party wall. To install it behind your skirting, for example, would be a complete waste of time since it would be bridged by the neighbour's higher ground level. The price you mention would be perhaps slightly on the high side for just 20 sq. metres and we would always suggest that you obtain three estimates. I have to ask, were you not aware of this potential problem before you moved in?  Did you have a survey and was any problem detected?

Q Thanks for your help with this. What you have said really does tally with what the contractor is proposing which is good. I just wanted to check as I know nothing at all about damp. I did actually get a survey done on the property before I moved in, but the surveyor failed to pick up the damp at all. I am currently in the middle of a complaints battle with Countrywide about this, but so far they refuse to admit any liability on their part. Thanks for the help


What level of moisture is a problem?

Q At what level are moisture readings indicative of a problem? I have a report that suggests that there is a damp problem because of readings of 5% w/w; 6% w/w and 8% w/w in three different walls. Also the moisture content in a skirting board was recorded as being 20% w/w to 28% w/w. These are very different readings. Do they all require action or is there a level which is normal and does not indicate damp which needs to be treated?
A The level at which the moisture content, not readings, is indicative of a problem would depend upon the material in question. You quote 5%, 6% and 8% readings taken from different walls but do not state how these readings were obtained.  If they were figures recorded from a hand-held moisture meter then as these instruments are calibrated for use on timber they would be wood moisture equivalents. It is not possible to quote actual moisture content of masonry/plaster when using such instruments. If they were obtained using a Speedy meter on site then they are of little value since these instruments do not differentiate between hygroscopic and capillary moisture when used on site. If they were obtained using the oven dry method described in BRE Digest 245 then they are accurate.

With regard to walls, a question often posed is, "When is damp damp?" To answer this question would depend upon your reason for detecting dampness in walls.  Surface moisture meters are known to be overly sensitive when used on masonry and this is sometimes used to the advantage of speculative damp-proofing companies touting for business. Structural surveyors will tend to protect themselves and will always draw their clients' attention to any dampness recorded. As a householder damp is probably only damp when it is having a detrimental effect upon the decorative finish.

With regard to timber you quote readings between 20% and 28%. If a surface moisture meter was used to obtain these readings then it is generally accepted that anything above 20% moisture content in timber should be considered at risk from fungal decay. The source of moisture responsible for this level of moisture content in timber should also be investigated and rectified.

If you would let me know how  your readings were obtained I may be able to expand further.


Who should I contact?

Q Hi I have recently had a survey done on a small 200 year old cottage. It has come back that a number of rooms have damp plus the kitchen floor is extremely wet indicating a leaking pipe or if that didn't cure it taking the kitchen floor up and replacing it. Downstairs in the front room the old beams go into the wall and he says that the wall they are fixed into is damp! Adding that the wood in the wall maybe rotting. My question is who do I get in to give me estimates for the work before I lower my offer? This is my first property which I am looking to develop. So I need to alter my offer accordingly. Would you advise pulling out or is it worth getting these things done? Thanks
A If it is a 200 year old property in need of improvement/development then a bit of damp and rot should not be a surprise. I suggest that you get at least three estimates from timber and damp specialist companies who are members of the Property Care Association (PCA), formally the British Wood Preserving and Damp-proofing Association (BWPDA). Also go to the Articles section of this site and read articles 4a - 4d inclusive which will be of great assistance to you. Armed with the prices produced by these companies you should most certainly re-negotiate your offer. What else needs doing that you could throw into the ring?


Correct damp meter reading?

Q Advise correct damp meter reading level for 5 year old property
A Most surface damp meters have colour coded zones - green, amber and red. Any reading in the green and lower amber zone is generally acceptable - above this further investigation is necessary. It is important to realise that surface moisture meters are sensitive and calibrated for use on wood only. They also react differently on different surfaces. Used on any material other than wood such as plaster or brick they are only a guide and the reading is obtained not quantitive. In a five year old property I would not expect any significant readings at all i.e. all in the green zone.

Greasy damp?

Q I live in a 1900 mid terrace house. I noticed over a year ago that small, greasy-looking patches have started to appear along the party wall, next to the fireplace, and around the fireplace too.  I have spoken to my neighbour and she has not got the same problem on her side of the wall. Recently, I put some sealant on the wall and painted over the affected areas. However, the patches have reappeared - and are now worse! The wall doesn't feel damp to touch but it is unsightly. Would welcome any advice.  Thanks.

A Very difficult to say what the problem might be without seeing it. If you sealed it (what with?) and the problem got worse then is likely to be damp related. Your neighbour (or the previous occupier) may have had the problem in the past and had a different plaster applied on their side hence it is not showing. You should get it checked out by a specialist who is a member of the Property Care Association and CSRT qualified.


Could laminate floor be causing damp walls?

Q I have a basic two up, two down old Victorian terrace. The front room floor is floor boarded, and the back room (plus under the stairs) is concrete. I had a laminate floor laid in the back room over the concrete about a year ago, and for about the last six months the internal wall in the front (that backs on to the under-the-stairs cupboard) is showing wetness (it looks wet rather than damp). I've had a damp contractor in, and he thinks the concrete floor is sweating, and causing the wet patch, as the building is so old he thinks it won't have a damp membrane in the concrete. He's recommending that to get the job done properly, the concrete floor should be dug up and replaced. Should I go ahead with this, or just rip the laminate up and relay carpet to let the floor breath better. If I go ahead with this and it works, will the wall dry out by itself, or would it need re-plastering?

A Difficult for me to speculate what the problem might be without seeing it.
It is assumed that the floor in the under stairs is the same as before i.e. no laminate laid, so only one side of the wall abuts the laminate - is this correct? There is no reason why laying a laminate floor on top of a solid floor should have any affect upon an adjacent wall. Rising damp is not under pressure and it will not be 'forced' elsewhere because a plastic surface membrane has been laid beneath laminate (we assume this has happened) The laying of the laminate and the damp wall are probably not connected but as said before it is difficult to say for certain without seeing it.

In any event do not dig up your floor just to incorporate a new damp proof membrane. There are available perfectly good epoxy surface membranes that are applied by roller and would probably be more than adequate in your circumstances - if it is actually necessary. It would also be less expensive, less disruptive and quicker to deal with the wall.


Neighbours - A damp nuicance!!

Q Our neighbours have their garden and soil built up high against our gable end wall and this is causing severe damp. They say as our wall is our boundary we are responsible for holding their garden back. Have you any idea if this is correct? Unusually, we appear to be responsible for maintaining boundaries on all 3 sides of our detached property.

A Your question is a legal issue thus I am not able to be of much assistance. I believe that if a neighbour's actions are having a detrimental affect upon your property it is regarded in legal talk as a nuisance and you would be entitled to take action. However action should be avoided whenever possible with neighbours as you have to live with them. What they appear to be saying is that if they decide to build a water feature against your wall you would be responsible for the protection of your wall or you must suffer the consequences?? This cannot be correct so I suggest that you take legal advice and try to resolve the situation amicably.


Would we have to raise the floor?

Q We have just had a survey done on a old end cottage, and the surveyor states that there are serious levels of rising damp. The downstairs has flagstones, and wood block flooring, although the kitchen floor has recently been laid with slate. There was no damp detected on the slate or the wood block floor. The flagstone floor which runs in the hallway, and the outer wall, had high levels of damp, along with the inner walls. As the cottage floor is level with the road, we would not be able I assume to have a damp proof course without raising the floor of the cottage. Am I correct in this assumption, and would we be crazy to buy this house? What kind of work and costs would be involved to do sort something like this out? Any advice would be greatly appreciated. Thank you.

A The fact that the floor in a property is level with the outside level does not prevent damp remedial works taking place and there is no need to change levels. Certain additional procedures may be necessary but these would be minimal. It is impossible for me to speculate on cost but get several quotes and negotiate the cost off of the asking price if you have your heart set on the property.


DIY DPC help required

Q Hi, I'm about to inject a damp course to my terrace house. Could you please answer the following:-
1. Do I need to take plaster off all the walls downstairs including the interiors?
2. Do I inject the outer walls from outside and interior including joining walls from inside?
3. Before its re-plastered I've been told to 'float it'? What is this, how and when is it applied?
4. Before I re-plaster can I apply a waterproof solution to the brick for added protection?

A To answer your questions in the order raised:

1. You only need to remove plaster from the walls in which rising damp has been diagnosed to be present. It must be removed to a minimum height of 300 mm past the last recorded moisture reading - not just one metre.

2. You may inject a wall from any side that suits you and the circumstances of the property. It makes no difference to the efficacy of the system provided you follow the correct procedures.

3. For re-plastering the first coat is a render coat comprised of 3 parts sharp washed sand to 1 part cement incorporating a waterproof additive in the gauging water. The second coat is a 'floating coat' of 3:1 with no additive. The skim finish is then applied.

4. What do you mean by a 'waterproof solution'? If you apply anything waterproof to the bricks before re rendering you will not get anything to stick since you will have made it waterproof - do not apply anything or you will have all sorts of problems getting plaster on the walls!

Forgive me for asking but why are you going to attempt this yourself? The questions you ask demonstrate you have a limited understanding of what you are going to attempt and you will not be able to provide a guarantee upon completion which has a value when you come to sell the property. You might not get it right and when you come to sell the purchasers surveyor may find a few problems and it will all have to be done again by a company in order to obtain a guarantee. How old is the property and does it really have rising damp? What type of system are you proposing to use?


Could boards and joists be damaged as well?

Q We are in the process of buying a new house. The survey results show rising damp. The repair costs are £1500 to re-plaster and inject damp proof course.  The report is only a visual one. Is it possible the floor boards and joists could be damaged?
A Any company that has made a diagnosis of rising damp has a duty of care to inform you that timber adjacent to the damp affected walls is at risk to fungal decay and should be inspected. If they have not done this then they have failed in their duty (and failed to conduct a survey in accordance with BS6576).  Well done for thinking about it and make certain you get it checked out before you proceed.


Are these prices fair?

Q We are in the process of buying a 1900 Victorian end terraced house and had a damp and timber survey done at no cost. We have had the report back and it doesn't sound too good. Tests showed high levels of internal dampness on the front bay window, gable wall of front room, areas of both internal/external walls of the rear room and all walls in the kitchen. As well as wet rot in the front room, he also picked up on the kitchen floor having felt damp proof course which is hiding problems. He has quoted us on damp proofing which is: £612.00 to insert chemical damp proof course to ground floor walls, £1,416.00 - remove/replace the complete living room floor, £75.00 - provide guarantee cover for rising damp, £75.00 - guarantee cover for timber treatment which in total is £2,178. As we know nothing about this sort of area is this a fare price? Also do you think companies that do free surveys add on extra costs?? Is there a cheaper way of doing this? Please help, we need your advice! Thanks

A You will have read on our site that we are not able to comment upon individual prices quoted since we have not seen the property.
You should certainly get more than one opinion - three at least. Try to get Property Care Association members and a CSRT qualified surveyor. You do not say if the price to inject a new DPC includes replastering. If not what have they said about the replastering which would be essential? We do not understand what you are saying about the kitchen floor. What is the original DPC? Did they not discover? The guarantee prices that you quote seem expensive.

Free surveys are always speculative and they naturally will be enthusiastic in their diagnosis and remedy since this is how they earn their living. Independent surveys and opinions such as those provided by me often save money as they often avoid unnecessary work. Whatever faults are found in the property should be negotiated off of the asking price or your offer price. You are quite at liberty to re adjust your offer based upon the cost of work necessary - this is usual. A sensible option is to engage the services of an independent specialist surveyor who does not have a vested interest in what is found. More often than not this saves money. You should also read our 'Getting on with the job' manual which may be downloaded from our web site as it will be very useful for you.


Can rising damp affect your health?

Q Can rising damp affect your health as my son who is 8 months old is always getting a bad chest and our wall is covered in rising damp?


A There is a lot of mythology about damp causing health problems. Spores produced by mould growing on surfaces as a result of condensation can cause respiratory problems but one tends not to get mould when rising damp is present. By breathing, perspiring, cooking and washing we as people introduce more moisture into the atmosphere in our homes than a few square metres of wall affected by rising damp will ever release. A thermally efficiency building combined with the provision of adequate dry heat and ventilation are necessary to provide a healthy environment during the cooler winter months. Inadequate heating, poor insulation and bad practices such as drying clothes inside all contribute to make an unhealthy environment. Are you certain that you actually have rising damp? Could it be condensation?


Will a laminate floor drive damp up a wall?

Q I want to lay a laminate floor in my dining room over an authentic tiled floor that I don't think has a damp proof course. If this is done will it cause damp to rise up the walls and if so what can be done to prevent this? The dining room is connected to the living room that also has the tiled floor and will be covered by carpet. Can you help?
A Laying a laminate floor over your dining room floor will not 'drive' moisture up the surrounding walls - Rising damp is not under any type of pressure. You will need to lay a suitable membrane over your dining room floor before laying the laminate in order that any moisture emanating from the dining room floor does not affect the laminate. Ask the floor manufacturer what they suggest.


What is the likely cause of my damp problem?

Q Our back boiler leaked six months ago taking out the whole ground floor. Floors were de-scabbled and walls re-plastered which was covered by insurance. We are end of terrace and have neighbours gardens that run alongside the length of our front and back gardens. The garden that backs on to the side of our house comes 2-3 feet up our wall. I have now noticed the wallpaper is peeling off of this wall. Do you think this damp could be related to the leak in 2005 or is it more likely to be from the neighbour's garden? The neighbours are council so would I approach the council or my insurers?

A Difficult to say without seeing it but from what you describe it sounds likely that the damp may be due to the high external ground against the wall. One possibility is that the original plaster was removed because of the 2005 incident and that the replacement plaster along the wall with the high external ground was not suitable for the circumstances hence you now have a problem. I suggest you start with your insurers as work that they paid for is now giving you trouble but you should also ask the council if they could lower the high ground or introduce precautions to compensate for the high ground.


When to do DPC? Do we tell the neighbours?

Q We're looking to buy a Victorian basement flat, which has damp marks up to 6 foot. They're persistent throughout the flat, even in summer months. We had a full structural survey, and a damp course was recommended with additional tanking in the bathroom.For this, we've received a quote for around £5,000 but we're unsure as to the disruption this will cause long term. In particular, we want to replace the existing kitchen and bathroom. But we've heard the replastering will take 4-6 months to dry out. Should we re-do the kitchen and bathroom BEFORE having the DPC?? Or will we have to rip everything out first, have the DPC and then wait up to 6 months before we can put in a new kitchen/bathroom?? i.e. will the flat be uninhabitable for all this time? Also, we share a couple of walls with neighbours. Do we have to tell them we're having the DPC? Could they stop us getting it done?

A We have answered several questions about basement flats already in this section. If you have damp marks 6 feet up the wall regardless of the season there is a problem and if it is in a basement flat that means it will be expensive to deal with it properly. Be careful because not many understand how to deal with complications in basements properly. We do not however follow your logic? If you put a new kitchen in now it will be against damp walls and will have to come out at some time in the future to deal with the damp. This will wreck the kitchen. How long the plaster will take to dry out depends upon what is being carried out. There are methods that could be used that reduce the drying periods but even if a sand and cement system is employed you should be able to install a kitchen/bathroom a matter of weeks after application and yes it will still actually be drying but you will not notice other than increased amounts of condensation.

You are required by the Party Wall Act to notify your neighbours of any work on the party wall. You should get your solicitor to check the lease because the cost of work on the structural walls may be shared between all of the lease holders in the block.

As stated before go very carefully if you are considering a basement flat. They are also more prone to condensation.


Can I use these short cuts?

Q Is it possible, once an injected damp-proof substance has been put into all the walls, to simply apply a waterproofing substance to the interior walls and then paper with a heavy embossed paper which can then be painted? Alternatively, I considered putting up boarding and dado rails which would effectively hide the unsightly salt line and damaged paper. I would appreciate your comments.
A It sounds like you want to avoid replastering. You have to remove the hygroscopic salts contained in the plaster as a result of the rising damp and the only way to do this is to re-plaster correctly. If you do not you will experience on going damage to decorations irrespective of what 'waterproofing substance' is applied to the original plaster surface. Dry lining is not to be advised since if it is not executed correctly and due to the limitations of a chemical DPC system it could cause other problems.

The successful outcome of any remedial DPC system is dependent upon three processes 1) the correct diagnosis, 2) the correct installation and 3) the correct re-plastering. There are no short cuts available such as you describe. If there were then all contractors would be using them.


Has tanking caused damp in kitchen above?

Q We are in the process of buying a Victorian stone built end terraced cottage and have just received the surveyors report. The surveyor comments on the plaster walls in the kitchen showing high signs of damp. The kitchen is above a 'tanked' cellar. Could the tanking of the cellar have caused any damp to rise? If so, what is the solution and would you advise continuing with the purchase of this property?
A Whether or not the tanked area beneath the kitchen would have an effect upon the kitchen walls above would depend upon the type of tanking carried out. If it was a cement based or pore blocking system then it is possible. If it was a cavity drainage membrane system then it would be unlikely. Whatever the cause it would be possible to remedy the situation. Get several estimates from damp proofing specialists and renegotiate the asking price armed with the estimates.


Damp front wall

Q We have recently purchased a Victorian terraced house which has a problem with rising damp mainly in the front wall (which has a bay window) but the damp also extends about 1 metre along the walls which we share with our neighbours. The front wall is externally rendered below the bay window. One company has suggested a chemical DPC and re-plastering (with a 30 year guarantee) whilst another has suggested the same work plus the removal of the rendering and its replacement with a waterproof render and wood float finish.  How can we tell if the re-rendering is necessary or not?

A Unless the external render is unsound - hollow - cracked - perished, there is no justification in removing and replacing it. It is probably a very hard dense waterproof render already and to remove it would cause damage to the underlying brickwork which is to be avoided if at all possible. Make certain when they hack off internally (which is essential) they do so 'gently' so as not to damage the external render.

Do I need a DPC as well?

Q If a property is being treated internally for structural waterproofing due to external yard level being approx 200mm higher than internal floor level, should the specialist installer also inject for horizontal DPC or not?
A In the circumstances you describe if it is an older property and the wall is suitable to receive an effective DPC system then one would expect a new DPC to be installed 150 mm above external ground level as well and internal plaster removed to a minimum height of 1.2m above internal floor level (1 metre plus 200mm) though higher would very probably be necessary. Circumstances may be different but it is hard to imagine what. I am not certain from your description if they are just dealing with the bottom 200mm and doing nothing else? If they are then it sounds like they do not know or understand what they are dealing with.


Small puddle from under skirting?

Q We have a damp patch on an internal wall, and have noticed water which is clear, in a small puddle coming out from under the skirting boards on both sides of the wall. It seems this water is soaking upwards in to the wall. There is a hole in this wall for central heating pipes to go through and we initially thought this was leaking but it has been replaced but has not solved the problem. Our house is 104 years old and the floor is quarry tiled throughout. There are also a couple of small damp patches elsewhere, but all on internal walls at the bottom. Could this be a damp problem or is it more likely to be a pipe under the floor? How can we check and who would be the best person to ask?

A If you have a small puddle then you have a leak - not rising damp. Rising damp is what is termed 'capillary bound' - it is not 'free water' as in the puddle. The pipe may have been replaced but there may still be a leak. Pipes generally do not leak - it is usually a joint of some sort or a valve that leaks and the water runs down the pipe and drips off. Not really able to comment on the other patches without seeing them. You should be able to establish whether or not any pipes are embedded in the floor and if so where they run. If the floor is original then it is very unlikely. Get a damp specialist who is a member of the Property Care Association and CSRT qualified to have a look.


Walls too thick for a DPC?

Q I am currently in the process of buying a 250 year old cottage and the survey has shown that damp is an issue. I have arranged for a contractor to provide a survey and quote for the remedial work required. He has told me that because of the thickness of the external walls, a conventional DPC would not be suitable and has suggested a method which involves coating with walls with a viscose membrane from floor to ceiling. He is estimating the costs to be around £25K which seems obscene to me. It is a large 3 bed property.  Are there any alternatives?
A All credit to the surveyor for bringing this to your attention - many would just drill the holes and take your money. It is true that the construction and thickness of some walls means that they are not suitable to receive an injected DPC so one has to look at other methods of achieving a dry decorative surface. What has probably been suggested is the fitting of a 'plaster membrane' (plastic dimpled membrane with a mesh to provide a key for plaster). This would be fitted from floor to ceiling however it may be sufficient just to apply a waterproof render up to a height of 1.2 - 1.5 metres. My advice is that you obtain several opinions from Property Care Association (PCA) member companies who employ CSRT qualified surveyors.


We were flooded - What is this damp measurement?

Q We live in a stone built cottage which is over 300 years old and has 18 inch thick walls. The walls are built of limestone, with a soil based cavity. The house also does not have any "footings" as such. The floors downstairs have been concreted over the soil footings and a damp plastic membrane has been put in. When we bought the house there was a lot of damp in the walls and even standing water on the floors. We had an injected damp proof system put into the walls and all the plaster chopped off to 1 metre high throughout the house. Ever since then (12 years ago) we have had no damp whatsoever in any part of the cottage. Unfortunately in June this year we were flooded out to a depth of 3 feet throughout downstairs and we are now in the process of drying out. We have not had any plaster removed as we felt the house would dry out naturally even though this would take more time. We have 5 de humidifiers and 2 blowers doing the work and things are drying out slowly. The insurance loss adjuster damp people have been and taken readings again this week. The floors are now around just over 20g/K according to the report and walls nearly the same. What should a "normal" reading be for a house built of this nature? Surely there must be some moisture still within the wall cavities and footings otherwise there would be some sort of subsidence and cracking? What does the measurement 20g/K represent?

A I am sorry to hear of the crisis you have been through. Neither I nor colleagues with whom I have consulted are aware of g/K as a way of expressing moisture content in a floor. It is however sometimes used to express the amount of moisture in the air - grams per kilogram of air.  What instruments are being used and what method is being applied to arrive at such a reading? We would be very interested to know.
We note you are leaving the original wall plaster on. You should be aware that the flood water could have driven what is termed the 'salt band' higher up the wall and it may now be at a height above the new plaster applied 12 years ago. A salt band is a high concentration of hygroscopic salt at the highest point of a rising damp complex. It remains in place even if the rising damp has been cured. Whilst it may have been adequately contained before the flood, the flood water could have caused this to move higher up the wall above the newer plaster - may be - just a warning that this could happen.
Please come back to me about the moisture readings. I would expect the walls and floors to take very many months to dry down and this will take even longer if a render is on the walls.


Living room floor lower than driveway?

Q We have a late 18th century house. The inside of the living room and dining room is actually at a lower point that that of the ground (driveway) outside by over a foot. We have started to get damp in the house and wonder what the fix would be. Is it to dig a gully around that part of the house so that it is level with the inside? Or some type of chemical damp proof or both. If chemical proofing where should it be in relation to the outside. i.e. should it be level with the inside or outside?
A It is assumed that the damp is on the wall adjacent to the drive. If at all possible dig a trench adjacent to the property incorporating a land drain at the bottom. Apply a suitable vertical barrier against the property and then backfill the trench. There are some CAD drawings on the Safeguard Europe web site that illustrate this procedure using a cavity drainage membrane - possibly under new build. For the record any DPC should be 150mm above external ground level where ever that may be.


Water coming up through floor?

Q We live in a terraced house about 100 years old. The downstairs wall, at the back of the house, where it joins next door has always had a damp patch on it, however recently moisture (appears to be clean water) is coming up through slight cracks in the asphalt floor, which seemingly was put down many years ago to cover the original flag floor. There are no water pipes in this area at all - is it possible for rising damp to actually do this? And to cure this would we need a damp proof course on the one wall and a new floor fitted?
A What you have described is termed 'free' water. If it is coming up through cracks in an asphalt floor then it is almost certainly not rising damp. Rising damp is 'capillary bound' which means if you stroke your finger across the damp surface your finger should not be noticeably wet. Are you sure water is actually coming up through the floor and the problem is not just condensation forming on the surface of the floor - which is not unusual? You need to be certain that you get what ever the problem is correctly diagnosed to avoid undertaking unnecessary work. The damp patch on the wall may well be rising damp but does a garden wall abut the rear elevation externally or is the gutter dripping etc.? Investigate and eliminate all possible causes before taking drastic action.


Water under my floor

Q I own a semi-detached house built around the 1930s.  A few weeks ago I discovered that there was a small damp patch just above the skirting board in the lounge - the wall paper had begun to peel away and some salty deposit on the plaster. The wall in question is an internal load-bearing wall dividing the lounge and the kitchen.  The kitchen has a concrete floor. The lounge has a suspended wooden floor - underneath the floorboards there is a void of about 75cm with concrete at the bottom (top of the soil). I removed some floor boards near the damp patch and on inspection saw water present (2cm depth) just around that area. I suspect this water is rising up the wall and causing the damp. There is no evidence of dampness on the other side of the wall (i.e. in the kitchen). Where has this water come form? I thought that it may be the water mains leaking so I arranged for the water supply to be turned off from the stop cock on the pavement out site. It is now over 4 weeks since the water has been turned off, but the water under the floor boards is still present. Could this water come from a neighbouring property with a leaky water mains? A friend has advised that it may be spring or ground water that is causing the problem. How can spring or ground water be 'diverted' or moved away from under the property (e.g. by putting sand or something on the concrete)? What is the best remedy and the cost involved?
A A 1930s property will have a damp proof course (DPC) in the walls and provided is being allowed to work correctly you could have a river beneath your property but damp should not rise past the DPC. Indeed I have surveyed numerous properties one of which had a stream beneath the floor and others with water depths of between 10cm - 30cm subject to the varying height of the water table. So it is not unusual to have water beneath a property. It is essential however that the sub floor ventilation is very good indeed - 9"x6" efficient air bricks every 1.5m in all external walls. By efficient we mean square pattern metal or plastic louver type but NOT terra cotta type as these are only 20% efficient and have the ability to bridge a DPC

You are correct to investigate all other possible ways by which the water may have entered the property and no doubt you have checked the plumbing on the kitchen side of the wall. One point however, in 1930s properties the DPC was built in at a level to protect the timber floors - about 8" beneath the timber floor level but when they in filled to create the solid floor for the kitchen they often bridged this DPC so it is not unusual to have damp in the walls surrounding a solid floor in such a property irrespective of the water under the floor.

Your local water authority is able to test the water to see if it has come from a main because it contains their treatment chemicals - chlorine, fluoride etc. so perhaps this is worth a try. If you put sand on the oversite the water would still be there in the sand but it would just be out of sight. If everything draws a blank your friend could be right but do not worry - just make sure it is well ventilated


What type of DPC is in a 1930s house?

Q In a 1932 solid brick semi detached 3 bedroom house in the black country what would have been the separator at DPC level?
A There would have been no 'standard' DPC material at that time but it is likely to be; bitumen felt,  poured bitumen or double slate. If the property has timber ground floors, to find out the type of damp course if it is not visible externally, lift a board in the under stairs cupboard next to the electric meter (they are usually short and loose there) and with a torch and mirror look at the mortar course just below the lowest part of the timber floor - usually about 200mm (eight inches) below the floor board level. You should be able to see the DPC.


Should I dry line damp walls?

Q I am installing a new damp course into walls with rising damp. Instead of re-plastering the internal walls to stop salt transfer I am thinking of battening and dry lining them. Have been in contact with the manufacturer of the treatment and they do not foresee any problem with this as long as the walls have adequate drying time in order to prevent dry rot occurring. By choosing this method can you tell me whether the guarantee would still be valid?
A Timber batten and plasterboard it not a method I would advocate on a wall with a history of rising damp. This is a recipe for dry rot and should be avoided (the wall may become damp for another reason in the future). I am very surprised that any manufacturer would sanction the use of such a procedure. Which manufacturer was it? Are you a contractor or householder and which type of guarantee are you referring to? - Product Guarantee or Process Guarantee? Hope to hear from you.

Contact Peter: Email - info@dampdecay.co.uk - Telephone: 015242 71794