Damp - Treatment Methods

Is this a damp cowboy?

Q We have a contractor locally who is stating to customers, that the tanking of walls will cure rising damp. They are informing customers that the drilling and injecting is not necessary once the walls have been partially tanked. He has written a letter to a customer stating that, "We do not inject and have not done so for 8 years now as drilling and injecting is outdated and unreliable". They issue xxxxxxxx Chemicals Insurance backed guarantees. I would appreciate your thoughts on this.

A It would appear that the contractor is a little ignorant of the facts. Does he just apply tanking slurry over the wall and then renovating plaster on top? What event is he guaranteeing against? Rising damp!!? If he is guaranteeing to cure rising damp then from what you describe he is doing nothing to stop it - he is just concealing it. The word cowboy comes to mind.


What is the reputation of Holland damp system?

Q What is the reputation of the Holland system for damp proofing? Does is work?

A There are many articles on the web about the damp control system developed in Holland to enable you to draw your own conclusions. We would only advise the use of a system which has third party accreditation in the UK from the Agrement Board - the Holland damp proofing system does not have an Agrement Board certificate.


Feed back on electro osmotic damp control system

Q I have rising damp problems in my 1890 Vic terrace (Sydney Australia).  My first question is have you had any feedback on the Electro Osmotic System to counter rising damp. It also claims to drive the dissolved salts back down out of the walls.
Second question is - my walls do not have a cavity and are originally a lime plaster. Is it safe to re-plaster the damp affected walls with cement based render or does it need to be lime based so the walls continue to 'breath'? Thanks for your help.

A We are very familiar with electro osmotic 'damp control' systems over here in the UK and since they do not have third party accreditation in the UK we would not recommend them. They most certainly would not 'drive the dissolved salts back down out of the walls'!! This would be physically impossible and perhaps illustrates one reason why we do not favour such a system - often contractors who market such systems introduce their own science and tell you things that you want to hear in order to make you buy - be careful!

You should re-plaster the salt contaminated walls with 3 parts sand to 1 part cement. There is no problem using this on sound brickwork. Make sure the joints are well raked out to help resist shrinkage cracks in the render. If you use anything less than this you are likely to experience on going hygroscopic salt problems. Look for a company who uses Dryzone which is a cream damp course system made over here but we know it is available in AUS in fact the Paramatta town hall was treated with it! If you get stuck come back again.


Physical or Chemical DPC?

Q We have recently bought a house which has some damp patches. We have contacted a couple of specialist damp companies to come and give us quotes. One company has suggested using injected chemicals and the other has suggested placing a plastic membrane in between the bricks which will work out very expensive. We intend to keep the house for many years however we are not sure which would be the best way to treat the damp. Do the chemical treatments really work? Which treatment would you recommend?

A My company installed Physical DPCs for years and there is no doubt that a physical damp proof course is the very best - it 100% stops rising damp but it comes at a price. Chemical systems are good and they will 'control' rising damp with many having third party accreditation. Both systems require re-plastering as well due to salt contamination but with a chemical system the correct re-plastering is even more important in order to control what is termed the 'limitations' of the system.

If executed correctly both processes will provide you with a dry decorative surface so it is a matter of 'pays your money - takes your choice'.

Does electro osmosis work?

Q Does electro osmosis work?

A Despite having been around for many years electro osmotic damp course systems have never achieved third party accreditation in the UK. In addition the Building Research Establishment publication 'Understanding dampness' is not very complimentary about such systems. You should be able to draw your own conclusions from this.


Flood damage and electro osmosis DPC problems

Q I had a water escape in my loft causing water damage to walls and floors. The house was dried out by the insurance company and walls re-plastered and re painted, ceilings replaced, bathroom tiling removed replaced etc.  We have been out of the house for nearly 6 months and the repair work commenced after nearly 1.5 months drying out. The painting was finished last week and now discolouration is forming at the base of some walls above the skirting. I thought this may be damp and contacted the damp proof contractor who installed the electro osmosis system for previous occupants of the house. The system has not been operated for the last 6 months. Initially the electric was off due to flood and then isolated until checked out. When the insurer's restoration people measured the water levels prior to installing the dehumidifiers they claimed the property was damp. I disputed this as we never had any visible signs and explained that the unit had been off. They didn't believe the system would work as a damp proof measure. During the course of the restoration work, two wires to my knowledge had been cut off (going across doors) and I don't know if the one running across the fireplace was cut of and plastered into the wall.  The installer informed me that the system should never be switched off for any amount of time and that the plaster on the walls contained an additive which is part of the damp proofing.  What I want to know is where I go from here. I am devastated as I was eager to get back in my home as the whole process has been one big headache with incompetent contractors. Can the existing system be repaired if so does the plastering need redoing?  All existing plaster on the affected wall was stripped back to the stone and redone. Any help would be appreciated.
A You state that the plaster was stripped back to the stone and redone. Was this by the builders repairing the flood damage? If so what re-plastering specification did the use? Did they take it right down to the ground behind skirting? If they did use a lightweight plaster on a wall with a rising damp history then you are likely to have trouble. What is the specification that the electro osmosis contractor states you should use? The additive he mentions is very much secondary - the actual sand to cement ratios is much more important.

Press the plaster with a compass point or similar. If it sinks in with relative ease then you have light weight plaster. Insufficient time has lapsed for there to be any significant accumulation of chlorides and nitrates in the new plaster. If the osmosis wires are reconnected and it is all turned on again then if the system works all should be fine but I would not hold your breath.

Other points:
Obviously the property was damp before the dehumidifiers were put in because it had just been flooded or are we missing something? It would also depend upon how they were measuring the moisture - was it the atmospheric moisture or wall surface readings they were relying on?

There are many who do not have confidence in osmotic type remedial DPC's. Whether it is on or off rising damp is a very slow process so it would not suddenly rush up the wall and transform the atmosphere - or are we missing something else?


Which method should I use?

Q I have had a couple of firms out to estimate on a damp proof course. One wants to take plaster off from the inside of room and another wants to double inject from the outside therefore less mess for us and quicker. Could you please advise which method is the best and which gives the best cure at end of treatment. Thank you for your time.

A Sounds like one company is cherry picking!

If rising damp has been diagnosed in a wall then it is essential that correct re-plastering is also undertaken if you want to achieve a long term dry decorative surface. Do not let anyone try to convince you otherwise. The wall surface will not dry out due to the fact that hygroscopic salt contamination will almost certainly be present in the plaster as a result of the rising damp and the only way to get rid of this is to remove the plaster that contains it. It will not melt away, evaporate off, go back to the ground etc.

Some companies will try and avoid re-plastering and cream off the most profitable part of the job which is the injection process. Do not let this happen. It sounds like the chap who wants to inject from the outside only is one of these and should be avoided. If he is talking double injection then he is using old fashioned materials. The best material now available is called Dryzone which is a very effective cream injected into the mortar course. There are cheaper imitations available but insist on Dryzone which comes in foil sausages. Goggle Dryzone for more information.


Does electro-osmosis work?

Q Does electro osmosis work?

A Electro-osmosis as a principal of physiss yes but when applied to function as a damp couse in a building? Electro osmotic damp proof course systems have been around for many years but they have never achieved third party accreditation in the UK from independent testing bodies such as the BBA (British Board of Agrement). You should be able to draw your own conclusions from this.


Dutch damp treatment company - to good to be true?

Q I have seen an advertisement for a Dutch Company 'Holland Damp proofing' who claim to cure all types of damp by inserting damp regulating bricks into the outside wall of a house. This system also claims that no re-plastering or decorating is necessary after treatment. This sounds too good to be true - can you please advise?
A We would urge you to research damp control systems very carefully - especially if they 'sound too good to be true'. Such a system does not have UK third party accreditation (independent verification that it works) so you may wish to look at other options that do. If rising damp is present in a wall then correctly formulated re-plastering is essential if a dry decorative surface is required. A specialist damp treatment company would be failing in their duty of care if this was not clearly explained to you.  No re-plastering would be a very attractive option as it would eliminate mess. Unfortunately this incorrect advice is used by some as a sales ploy to attract you to pay for the profitable element of the work and the result is often a frustrating long term dispute as salt contaminated wall plaster will never dry out.


What do you think of the Schrijver system?

Q What do you think about the Schrijver damp control system?
A In the UK the Schrijver System does not have third party accreditation from an independent body such as the Agrement Board to confirm that it performs as claimed. There are numerous articles about this system on the web that will help you to decide if such a system is suitable for your requirements.


Dutch system says that I do not need to re-plaster?

Q I have a 100 year old house with 9" solid walls which has been in need of damp-proofing for some considerable months. I have had some quotes and they all say I need to re-plaster. I have seen an ad for a firm with a Dutch system which they say "Damp-proofing without the need for re-plastering". If all the other firms say it needs re-plastering why doesn't the Holland system? I would be grateful for your views.

A Any system or procedure that claims to prevent or control rising damp in a wall and also claims that no re-plastering is necessary to achieve a dry decorative surface should, in our opinion, be viewed with a considerable amount of caution.

Rising damp in a wall, where the water is derived from the ground, brings with it in solution salts and minerals that accumulate at or near the surface of a wall where evaporation takes place. The greatest concentration of these salts and minerals in a rising damp complex is at the highest point of the rising damp, usually in the wall plaster and often referred to as the 'salt band'. Salts derived from the ground that are deposited in the plaster as the water evaporates are mainly chlorides and nitrates. These salts are what is termed hygroscopic which means they have the ability to attract moisture from the atmosphere in much the same way as a salt (sodium chloride) in a steamy kitchen. This means that even though the rising damp may be effectively controlled, decorative spoiling is still likely to occur as a result the hygroscopic actions of the salt contamination.

We do not know of any remedial damp course procedure installed into a wall that can reverse, cancel, displace or negate the actions of chlorides and nitrates that have contaminated wall plaster as a result of rising damp. Any organisation that claims' re-plastering is not necessary when dealing with walls affected by rising damp should be viewed with scepticism and you should conduct very thorough research before committing yourself.



Is this Schrijver system correct?

Q Is the Schrijver system damp control system effective for a 30 year old bungalow which has off peak storage heating? The lady of the house has constant condensation and damp, she collects water in containers in all rooms especially in cupboards. I am her electrician and friend. Schrijver system has told her she has rising damp.
A Bungalows are notorious for suffering from condensation and we would be 99.0% certain that a 30 year old property would not have rising damp due to a defective damp proof course. We are aware of a case that went to court recently and Schrijver were ordered to return the money as it was clearly demonstrated that their system did not do what it was claimed it would do in the circumstances  for which it was installed (it was a case of condensation control).

The condensation problem needs to be tackled and you should look at adequate heating, adequate insulation and the occupants life style. Stop immediately any internal clothes drying - extract kitchen and bathroom water vapour. The lady should also consider purchasing and using a domestic dehumidifier. It is the occupier who is generating the water vapour that eventually forms as condensation and some find this difficult to comprehend. The problem will disappear during the summer so do not let this fool you.

You are a good friend to intervene on her behalf - probably a good electrician as well!


Does Dryzone work?

Q Does Dryzone work?  I have one wall that is particularly damp. The internal wall was rendered with cement which has been removed but there is no sign of the wall drying out. After serious consideration and much reading I am coming to the conclusion that a DPC is the answer - but which one - is Dryzone OK?

A Dryzone has third party accreditation not only from the UK but also Germany that basically says - yes it does work! A bare exposed brick wall that currently has, or has had rising damp will never dry out completely due to hygroscopic salt contamination so do not wait in vain for this to happen. Dryzone is the original of its type and almost certainly the best product on the market for the control of rising damp. There are other cheaper imitations around but the level of active ingredient in these is tiny compared with Dryzone. It is important to remember that injecting Dryzone is only part of the process. Using the correct specification to re-plaster is equally vital.


Limitations of a chemical DPC?

Q I've read an information sheet about Dryzone and would like some advice on the statement that 'the base of the wall may always remain damp due to the inherent limitations of the actual injection damp proof course'. Would you be able to explain please what the inherent limitations are and the extent of the dampness at the base of the wall? On a related point what would be your reaction if Dryzone was injected into brickwork rather than into mortar?

A The statement that you quote relates to all chemical DPC systems - not just Dryzone. A chemical DPC is a band of water repellent material that will never 100% reach all areas throughout the thickness of a wall, unlike a physical DPC. As a consequence it is known that the lower section of a treated wall will always have some dampness present - this is what is termed a 'limitation' of a chemical DPC system - but the rising damp has been controlled. This is one of the reasons why the replastering specification in conjunction with the DPC is so important as it has, amongst other things, to be able to control the limitations of a chemical DPC system at low level.

What is the point of injecting bricks? The only continuous pathway for rising damp is the mortar. If you had bricks of steel and sponge mortar you would have rising damp but if you had sponge bricks and steel mortar there would be no rising damp. Therefore if you create an impervious mortar course by targeting it, you create an effective DPC. If injection took place into the bricks only it is unlikely to diffuse adequately into the perps between the bricks and its effectiveness would be limited. Injecting the bricks has been discredited for many years now but many, perhaps out of ignorance, still drill and inject bricks. I hope the above assists your understanding further.


Chemical or Physical DPC?

Q We are in the process of buying a large semi-detached property aged about 175 - 200 years old. A full structural survey was done, with the result being there was no evidence of a DPC, with rising damp evident in the walls. What will be the most effective type of DPC for a property this age? The Surveyor said that a Chemical DPC would be suitable. But on a previous property of a similar age that we looked at, that Surveyor recommended the more 'traditional' physical DPC. I'm happy to have a Chemical DPC installed if it is 'up to the job' or should I go for the physical DPC which I know will be more costly, but will it weaken the structure? The work will obviously be done by a recognised company (not DIY).

A You did not state the method of construction but in virtually all cases a chemical DPC combined with the correct re-plastering to the correct height is sufficient. Do not let contractors use a plaster type called 'renovating' or 'limelite' as our experience has shown these materials are not up to the job in the long term. Insist on a 3:1 sand:cement render. The most modern and seemingly most efficient chemical DPC system is called Dryzone which is a cream like material injected into the wall. Other cheaper imitations are available so be careful as their active ingredient content is significantly less. The undersigned has many years experience of installing physical DPC's and to be honest with modern chemical systems being as efficient as they are a physical DPC is not worth the extra cost or risk.

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