Damp - Diagnosis

Which company do I believe?

Q I am in the process of buying a house and to be safe decided to have a damp proof and timber check done. I had one who was recommended by the estate agent who has done a lot of work for properties who I cannot find registered anywhere. I had one also done by the damproofers who I have used before who is registered. My dilemma is that the registered one brought back a lot of problems so I told the estate agent so we could perhaps get some cost off the property. I did show them the report. The registered one brought up as well as damp that the timbers under the room and hallway had partly been replaced and bolted with copper coating at the end but that no damp proofing between them and the masonry, so the estate agent sent in the unregistered company (I think) to check and he says they are fine. Please can you advise as one says fine and the other has totalled to £1,500 so far which is a lot for me to have to pay out.

A You say that one firm is registered and the other is not? Registered with whom? Please explain. You are right to be cautious however. Obviously it is in the estate agents interest for there to be as little wrong as possible but it is also possible that the firm they put in have been negligent in which case you could have a case against them if you purchased relying on their survey but this is a lot of hassle you could do without. Why don't you arrange to meet the 'registered' company at the property and ask them to point out to you (perhaps accompanied) exactly what they have found. If they refuse or play awkward you may draw your own conclusions. I would also suggest that you arrange for a third opinion form a company who is a member of the Property Care Association and make certain that the surveyor is CSRT qualified. Look again at my web site and read Informative Articles 4a - 4d inclusive. You should find it very useful and informative. Your situation is a very good example of why an independent survey conducted by someone like myself would be of great assistance.


Am I being fobbed off?

Q Please can you give me some advice. Over the last few months I have smelt a damp smell in our living room and it appears to be coming from under the front window,there is no sign of damp on the walls. I contacted our insurance company and asked them if there would send someone down to inspect our property due to having flood damage around the front and the back of our house. We have concrete floors throughout our house and never had any water enter our house during the floods. An inspection was done and the report said that we had seventy per cent moisture in the front wall of the house and also in the interior wall. The advice was to leave it because it is drying out nicely. The bricks are wet up to the damp course but there's no sign of damp inside the house. I am concerned about this report as I feel like they are just fobbing me off.I would greatly appreciate your advice on this

A I do not understand how they are quoting % moisture content as high as you report unless they took samples away for analysis. If they have quoted you this figure from a hand held surface moisture meter then the good ones are calibrated for use on wood - if used on any other surface then the result obtained is not quantitive. If you are concerned about the report you will have to engage the services of an independent expert and seek their opinion. If you let me know where in the country you are I may be able to point you in the right direction.


Contractor says the plaster is at fault - not their DPC

Q I have had a survey done that has highlighted a number of high moisture readings in the walls. There was a silicone damp proof course installed in 2001 and the installation company have recently inspected their work, coming to the conclusion that the subsequent replastering carried out was at fault. They claim there is evidence of hygroscopic salts. Does this reason sound feasible? What questions should I be asking?

A How did the contractor arrive at their latest conclusion? What is different now and what are they seeing now that was not there in 2001 when they made their original diagnosis that a new damp proof course was required? In other words how do they make one diagnosis to their advantage in 2001 and another to their advantage in 2006 possibly based on similar evidence? Did they arrive at their current conclusion using the same type of meter they used in 2001?

How have they tested for hygroscopic salts? They are not normally visible. Contractors often confuse Sulphates which tend to be visible and usually originate from building materials, with Chlorides and Nitrates which are hygroscopic salts usually derived from the ground.

Have plaster samples been removed for salt and composition analysis? If so who analysed them? Have you seen the report? Who did the re-plastering after the DPC? What advice/recommendations/specifications were enclosed with the original report in 2001 with regard to re-plastering? Were the consequences of getting the plaster wrong clearly pointed out in their original report? That is probably enough to be getting along with for now!

Incorrect re-plastering is a common occurrence if it was not undertaken by the DPC contractor. Irrespective of this the contractor was engaged as an expert and has a duty of care to provide the correct specification that should be used following the injection of a remedial DPC and to point out the consequences of not adhering to it or getting it wrong.

Good luck and let me know how you get on.


Who should I believe?

Q I have had a damp test done by two separate companies on my 120yr old terraced property; the readings came out at an average of 12-14% throughout the ground floor. One company has said that the DPC needs to be redone as the damp is over 10%, the other has said that it would only need doing once it reached 20%. The house has previously had a chemical DPC done, the first company that inspected and advised that a DPC is required are a new contractor, the second that said it was not necessary to re-inject is the company that did the DPC 7 years ago so it is under warranty to them.
Am I being given correct information or is it a case that one company just wants my business and the other doesn't want to shell out on warranty work?  Is there a recommended percentage at which a DPC is redone?

A This is an excellent example of separate contractors who have inspected your property - each demonstrating their own vested interest in their diagnosis and recommendations so I am are therefore not unduly surprised by their differing conclusions. I assume that both companies used surface electric moisture meters when conducting their inspections however when used on a wall it is not possible to quote an accurate % moisture content from such an instrument since most are calibrated for use on wood. Such instruments when evaluating a potential rising damp situation should only be used as an 'aid' only in the diagnosis procedure - they are not definitive.

Forgetting technical issues for a moment, and assuming a surface moisture meter was used I understand what the figures represent and we would regard them as low. If the company responsible for the original treatment is satisfied and no visible surface deterioration is evident then I would not worry. Increased moisture meter readings are caused by a variety of circumstances but the diagnosis or significance of the cause sometimes depends upon how the user of such an instrument earns their living. Your case highlights the benefit of having an independent surveyor inspect the property


What is this diagnostic process called?

Q Some years ago I saw a program on damp in houses. They had a professor bloke on who to test the level of damp in the walls of a property, first drilled the wall with a masonry drill, caught the dust on a piece of card, placed it in a cylinder type container and shook it, then he weighed the dust. This he said was the only way to obtain a true level of the damp in the wall? What is this process called?

A The process you refer to is sometimes called a 'carbide test' but it is more commonly called a 'Speedy Test' named after the Speedy Moisture Meter which is the actual instrument employed. The process is as follows: A weighed amount of material to be tested is introduced into the sealed container of the instrument and mixed with a measured amount of calcium carbide. They are shaken together and any moisture present in the sample reacts with the calcium carbide to produce acetylene gas. This exerts a pressure inside the sealed container which produces a reading on a gauge on the bottom of the container and this is calibrated in percentage moisture content.

It is not however the only way to obtain a true level of damp in a wall. If a Speedy is used on site it is very important to realise that the readings obtained are virtually meaningless. This is because the reading obtained is the 'total moisture content' of the sample being tested which is not sufficient to draw any meaningful conclusions. It is essential to know the hygroscopic and capillary moisture content (both of which together make the total moisture content) of the sample before drawing any conclusions and this is not possible using this instrument on site. There is a great deal of 'bamboozle factor' involved in the use of this instrument by many people using it who do not understand its significant limitations if used on site. A laboratory oven dry method (described in BRE Digest 245) is the best method to analyse a sample.


Damp found but not asked for!

Q We are currently trying to sell our property and have had a valuer round, then due to a mistake, also a surveyor who conducted a homebuyers report. Neither of these found a single bit of evidence of any damp; however the homebuyers report said a timber specialist would need to come round to inspect the wood as he was no expert. A timber specialist came round to inspect the timber, but also, without being asked did a damp report and low and behold he discovered damp! He said he was getting quite high readings in a 6m section from the wall behind the stairs to the front of the property. We only moved in two years ago and had no issue of damp brought up then other than a tiny bit round the electric box (under the stairs) where there is a hole drilled in the wall. We were told that this wouldn't cause any problems. (He saw this report as he was asking to see if there was one of any kind to do with any work that had previously been done). There is a damp proof course fitted and not a single shred of evidence inside or outside of any damp - no tide marks, no plaster crumbling or anything. But, this guy says we would need to strip back this section of wall, put new DPC in then re-plaster and put in new skirting boards...he isn't an independent surveyor as he works for a DPC company so I can't help thinking this is highly suspicious. What do you think we should do next? (The property was built in 1895)

A What do your purchasers think? Do they know about the timber inspector's damp report? It is possible that he may have been more vigilant than the surveyor (it's in his interest!) and there may be something there but if it is not causing decorative spoiling is it really a problem? The old question of when is damp damp comes to mind! It may be an area of wall to 'monitor' over the years but from what you describe drastic remedial action may be over the top at this stage. The bottom line is you will have to satisfy your purchasers if you wish to sell or obtain the services of a truly independent surveyor such as myself  who has no vested interest in the outcome of their imspection.


Persistant damp patches

Q We moved into a property in August which had a Damp Proof Course done in February of the same year. There are three recurring patches of wet that we're not quite sure are 'damp'. One being under a window - seals/drains have been checked, the area has been covered with plastic sheeting but the patch of wet still appears. The other two are either side of the chimney breast about half way down. We have paid out for a roofer to inspect the chimney etc and all seems fine. All three patches dry out and reappear with the slightest bit of rain. If you think that this could still be a 'damp' problem from the information I have given you, what do we do next?

A If you had a new damp course inserted only last February, then it is almost certain that the wall(s) will still be drying down. If you are seeing visible 'damp' marks that appear and disappear, subject to the weather, then something is wrong. You state that all seals etc. are all OK and you even covered the area with plastic sheet yet the patch beneath the window still appeared. The symptoms that you describe, especially in the area of a chimney breast, sound like hygroscopic (moisture attracting) salt contamination. These salts, mainly chlorides and nitrates, enter the building either as a result of rising damp or as a by product of burning coal - hence the chimney breast connection.

It is assumed that who ever did the damp course work also carried out the necessary re-plastering. If they did not then why not? Please be assured that a wall that has been diagnosed to have been affected by rising damp will have to be re-plastered to remove the salt contamination introduced as a result of the rising damp. Has the re-plastering been undertaken? The side of your chimney breast may be contaminated with salts as a result of moisture ingress that has now been cured. You may now be left with historic salt contamination which will appear damp in certain weather conditions and even show on a damp meter but the cause may have been rectified.  On the other hand moisture could still be getting in!

Have you called back the original company and asked for their opinion? If so what did they say? There are many possibilities and sometimes it is better to discuss this type of problem rather than type pages of 'may be's'. Please feel free to call me to discuss the matter in greater detail.


Sample of damp?

Q I need to send a sample of damp but don't know where to send it as I want to know what affect it is having on mine and my children's lives.

A A sample of damp what? What do you want to learn or know? What analysis is required? What are your symptoms? We would like to be of more assistance so if you could provide more information on the situation and circumstances we may be able to help.


Could spring be causing rising damp?

Q I have seen a lovely stone cottage and agreed a price, but when I received a copy of the surveyor's report, it identifies 'rising damp'. I believe there to be a spring in the back garden which has leaked over the years and wondered if this is the cause of the dampness. The house itself is immaculate and so is the plastering, but the paint has started to peel off around the skirting board in the living room.  On closer inspection, I feel that the gable wall has been dismantled at some stage as all the stonework doesn't blend in with the rest of the building. Should I be suspicious and withdraw from the sale?

A A property could have a spring, a lake, a river or even the sea in its back garden and whilst some of these may make the ground near the property more damp none of these would be responsible for any rising damp that may be present in a property; any rising damp would be due to the lack of an effective damp proof course. Old properties will have had maintenance and repairs undertaken over the years so do not let evidence of this put you off. The questions you are asking us should be directed towards your surveyor. Have you telephoned and discussed your concerns with him? If not do so but make a list of your concerns first in order not to forget anything. All suspicions are able to be investigated and conclusions reached. Obviously we are not able to advise you whether or not to proceed with a property purchase.



Moisture and salt testing

Q If I was to get a plaster test done for moisture and salts on my property after 12 months of a damp proof course being installed, where would they take the sample from e.g. height from ground, and what area size would be removed for testing?

A Testing plaster and conducting a moisture profile so soon after the introduction of a new DPC is unusual and likely to be inconclusive. Provided the wall suffered from rising damp before the DPC was introduced we would still expect it to be damp now as it takes a very long time for it to dry down.

If you are looking for ground derived salts such as chlorides and nitrates then if present, they would only be there in very small quantities indeed, if at all, as it takes many years for their concentration to build up in any quantity at a surface where evaporation takes place. Such evaporation would only be taking place from the surface of new plaster if incorrect plaster has been applied following the introduction of the new DPC. Correct re-plastering should not have any significant moisture increase.

It is more important to have the composition of the render analysed to check that it is in accordance with the specification stipulated by the product manufacturer of the materials injected.

To answer your question what height from the ground should a sample be taken? This depends what you are looking for and what you are trying to establish.  If you are looking for salts the greatest concentration will be at the top of the rising damp complex where ever this may be. Salt levels will always be low at or just above skirting board level which for some unknown reason seems to be a common site from where samples are taken. With regards to moisture it is known that it will always be damp at low level but this would depend if you are testing the masonry or just the plaster. A moisture test should report two results - 1) The air dry or hygroscopic moisture content and 2) the capillary moisture content. These two combined together make up the 'total moisture content' of a sample. Be careful however as the air dry moisture content can be significantly affected by contamination - hence hygroscopic moisture.

The size of the sample needs only be small - say 50mm square. If moisture content is to be checked it needs to be sealed and transported in a small air tight container for obvious reasons and tested ASAP.

Why do you need a test, or why have you been told you need one? What is the problem?


Do I have rot or rising damp?

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 effected 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 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 affected apart from some flaking of emulsion at 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?

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 certain amount of 'ventilation' was happening through the floor itself. Now that you have laid a laminate floor this has been prevented or drastically reduced resulting in a humidity build up in the sub floor void and probably moisture accumulating beneath the laminate on top of the flooring/chipboard. Sub floor ventilation was probably poor originally but this just made it worse. It also sounds like sub floor condensation might 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 engage an independent expert such as ourselves or obtain several expert contractor opinions about what exactly is going on and then decide if you want to attempt it yourself. You should use contractors who are members of the Property Care Association, formally called the British Wood Preserving Association. Please contact us again if you have any queries or when you receive the reports as we would be interested in learning the outcome.


Damp caused by cavity wall insulation

Q I live in a 1930's semi detached house and had mineral wool cavity wall insulation installed about 18 months ago. About two months ago I noticed a damp patch in the hall just above the skirting board on the long side wall of the house. That seems to have been caused by a combination of an air brick sloping backwards and letting water in with a combination of a 'mortar bridge' that I discovered in the cavity above the DPC. What is more worrying is that further investigation revealed dampness further along the same wall in the kitchen. I've opened up the floor in the kitchen and to me the brickwork below the DPC looks dry (other than at the very bottom in the angle where it joins the sub floor). I found that the insulation had slumped down below the level of the DPC and was resting on damp building debris in the cavity. The insulation appears to have become compressed and is damp.   It seems that the dampness in the insulation has absorbed into the brickwork above the DPC.  I understood that mineral fibre should not absorb water. 
I've had someone in from a local 'damp and timber treatment' firm who diagnosed rising damp, recommended a chemical DPC and clearing out the debris from the base of the cavity. I'm not convinced about the chemical DPC but wondered whether the clearing of the cavities and ensuring that the insulation isn't in contact with damp material would help. Your advice would be much appreciated.

A Damp problems caused by cavity wall insulation are not unusual and it sounds very much like you have made a good diagnosis yourself. Mineral wool in its expanded form in theory should not conduct moisture (but some say it does) and though we do not know for certain it seems likely that in its compressed form it might be able to do so more readily. If the dampness was not present before the insulation was introducedand nothing else has changed, then logically a consequence of installing the insulation is the dampness your property is now experiencing.

One point frequently overlooked is that the action of hammer drilling to install cavity insulation dislodges mortar within the cavity which then accumulates at the bottom and sometimes causes a DPC bridge situation within the cavity. Do not waste your time or money with a chemical DPC at this stage. We would suggest that first of all you clear out the bottom of the cavity but who should do this? Have you had the insulation company back and asked for their opinion? From what you describe they may have caused the situation so they should rectify it? Another point to consider for the future is that you may wish to apply a surface silicone onto the external face of the brickwork to reduce the risk of moisture transmission across the cavity at a higher level.


Surveyor missed the damp!

Q We moved into our house 4 months ago and we noticed after taking of the wallpaper damp in the walls. The old owners said that they had no problems with damp on their additional housing questions form and that damp coursing was done in 2002. Our solicitors have stated that they sent us a copy of the guarantee which we did not receive (I have emailed them). We also have damp in the corner at the bottom of stairs and underneath which is an internal wall.  We have a chimney breast at the back of this of which they boarded up.  We were told that because the air could not circulate it has gone into the walls and plaster could this be correct? The same thing has happened on another internal wall which backs onto our neighbour's chimney.  He has a Gas fire instead of an open one so not sure if there is sufficient ventilation. Where do I stand on that? We only had a basic survey done by Countrywide surveyors and they did not pick it up. I need to know where I stand as we can't really afford to have immediate works done on the house.  Oh and it was built in the 1900s.

A You should get the company back who carried out the work in 2002 and ask their opinion. If this is not possible or they identify a valid reason why it is not their responsibility get three reputable companies in to inspect and report their findings. Send copies of their reports to Countrywide and ask why they did not detect the damp. It does not matter how basic Countrywide's survey was - they had a duty of care to you, their client, and if they failed to detect any dampness present then they failed in their duty of care and could be held liable. Take legal advice and check that you may be covered for legal expenses under your house insurance.


Damp has returned - Help please?

Q Hi I am selling my house. I've only had it a year. I had a survey when I got the house and had a damp course done then but now I am selling the damp has come back. Can you tell me what I can do or is there any one I need to talk to about this matter? I have sold the house but the buyers will not budge on anything till I sort this matter. Can you help please?
A You need to get the contractor back who treated the damp when you bought the house just a year ago and they should sort it out if it is their fault. If it is not their fault they should tell waht the cause is to enable you to rectify the problem


Surveyor failed to find any damp

Q I moved into my 1900 mid terrace last July. Had homebuyers report done- stated no sign of damp and therefore they assumed DPC working efficiently? A short while after moving in I noticed painted walls yellowing in places on a couple of interior walls and paint flaking off. Under stairs cupboard smells damp. Now I notice plaster in places going soft and sinking in mainly around sockets. Plastering very lumpy in some places. Do I have rising damp/dry rot roughly 3-4 ft up wall? Also when I had survey done it pointed out excess water in yard due to neighbour's downspout discharging into my yard not into drain. This has now been corrected but could this have caused the problem? I have a dehumidifier on several hours per day and it needs emptying almost every day. It holds 16 litres and humidity level is 85 when I turn it on then decreases to 65. Thanks

A If as you say you paid for a Homebuyers report and the surveyor stated that no signs of damp were detected and now some three months later you have damp showing, then you should certainly request that the surveyor who undertook the inspection revisits the property as he may have been negligent and you may have a case against him.

Flaking paint is not necessarily indicative of damp and it could for example be caused by poor decoration preparation. You also state that the plaster around the sockets is changing. This could be due to new electrical sockets being recessed into a lightweight plaster rather than a sand and cement render. The neighbour's downspout discharging into your yard rather than a drain would be unlikely to have an effect internally. What is of concern is the volume of water that your de-humidifier extracts. You do not state how many people occupy the property but 16 litres extracted during a day is a lot. To extract this volume of water it is very likely that you are drying clothes internally and possibly do not have mechanical extraction in the kitchen or bathroom. This level of water vapour in the atmosphere would almost certainly condense in unheated and poorly vented areas, such as your under stairs cupboard, causing mould growth and hence a musty smell.

You may want to consider obtaining the opinions of two or three damp specialists who are members of the Property Care Association or an independent inspection by someone such as ourselves before you ask for the Homebuyers surveyor to revisit the property - this way you are forearmed.


Should I believe an honest opinion?

Q We have had a surveyor from a building firm who deal with wall tie replacements, damp proofing, dry rot etc. On inspection he has given my property the all clear of the problem at present and has advised another inspection in 3 -5 years. This is excellent news as my property is about to exchange contracts. It was built in 1929, should I take his advice?

A It is in a contractor's interest to find work and from what you describe he should be commended for providing an honest opinion and what I hope is a correct diagnosis. Without inspecting the property I am not able to advise you on what course of action you should take. You do not say if you are moving into the property or moving out of it.


What type of survey is required?

Q My girlfriend is in the process of buying an 1890 terraced property. The valuation survey has stated that the property has dampness to ground level walls and unevenness to ground level floors.  Should she commission a damp survey? Or should she request a quote from a damp proof specialist to assess the cost of rectifying the problem?
A She should have a survey undertaken by a suitably qualified (CSRT) damp specialist who, if they work for a building preservation company will almost certainly be able to provide you with an estimate for the work that they deem necessary. On the other hand she could have an 'independent' damp  survey undertaken by someone such as us who has no financial interest in any work that may be considered necessary as a result of the inspection. We offer this service. Whilst the second option will cost money it very often saves money by only recommending work that is necessary and justified. If you could let us know which part of the country you are in we may be able to help or point you in the right direction

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