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Cavity Wall insulation and damp - how to induce liability
 Started by  neilcharlton
 18 Jul 2009, 5:35 PM

Like a few others on this forum our house is having damp problems only after the cavity wall was filled. its obvious the wool is bridging the gap and water penetrating into the inner brick / wall.
we had the installers out once many years ago but they just fobbed us off and the problem went away for a few years, now its back.
the wool was installed in less than half a day and i think they spent about 30 min on the site survey.
i've heard there is a correct method of survey and installation and i wanted to ask the forum members what this procedure is.
my reasoning behind this is that its difficult to prove the wool is the problem how ever it shouldn’t be too hard to prove the installers failed to do a good job or failed to do an adequate site survey in the first place.
i imagine its going to be a battle for us to get the installers to remove it !
my reasoning behind this is that its difficult to prove the wool is the problem how ever it shouldnt be too hard to prove the installers failed to do a good job or failed to do an adiquate site survey in the first place.
i imagine its going to be a battle for us to get the installers to remove it !
Who put wool into cavities?
Usually either technical foams are used or mineral fibres.
There was a reason why the cavity was build in the first place- to keep the internal wall dry.
Putting wicks between a wet surface (the external wall) and the supposed-to-be-dry internal wall is rather stupid. The only one who is to blame is the one who paid for job.Well, he could blame the ones who tought him/her the laws of physics on the other hand....
technical foams are used or mineral fibres - it probably was this , it just looked like yellow wool when i removed some.
the job was done through a governement grant stay warm , they came knocking on doors telling people they could have it done for free.
For a temporay solution a ventilated cavity could be fixed to the outer wall. This would keep away the driving rain and reduce the moisture content in the outer wall.
Mind the roof overhang, the reveals around windows and doors, these have to covered/protected against rain ingress as well.
For the missing DPC a chemical treatment of the walls/foundation could offer a solution to stop the capillar effect sucking moisture from the ground. This is a difficult enterprise, only a contractor giving a full guarantee should be employed to do such a job.
In the medium/longterm one has to keep in mind that from 2019 all buildings undergoing a major renovation have to have a net zero-energy demand when the job is finished.
See here:
One needs a good civil engineer to oversee this type of renovation, hard to find in the current market.....
Hi - your tale is a warning to us all, eh?
If your walls are letting damp through there is a fundamental problem with them, porous brick, the mortar needs repointing or the gutters/downpipes are leaking or blocked.
You may get away with a cheap quick fix by using Thompsons water seal or similar to coat the walls to prevent more damp coming through, but a permanent solution would be expensive. I think external wall insulation would be my choice, which would stabilise the wall, insulate some more and provide a new external weather surface to resist water penetration in future.
Although you may get some compensation from the installers (doubtful!) I cant see how anyone could remove the cavity wall insulation in any cost effective way
I was luckier than you.
I discovered the problem before insulation was fitted, when I drilled through the wall.
I was fitting a conduit and drilling through the outer wall, I realised that the drill was covered in rotting wood from the inner wall (in a false ceiling area).
I discovered I had drilled through an old lintel, above a rear window, that was made of wood - which was rotting.
I removed a brick, in the inner wall, a inserted a webcam.
When it rained, you could see water running down the inner wall surfaces - we have never suffered damp problems.
On investigation, I discovered that the slate roof did not fully seal the rain out and if we had a south-westerly wind the rain poured into the cavity between the bottom row of slates.
I do not know the cure apart from a new roof - which I can never afford.
I am glad I found it as I was waiting for Warmfront (the gov dept) to inject mineral wool -- The yellow wool refered to, and would've had the same penetration problems.
On a bright note, if warmserve had installed the wool - they would hve to remove it if theres a problem that existed before installation and they hadn't spotted.
contact warmfront and argue it with them.
EU regulations demand now the dynamic calculation of the dew point. Most installers never heard about it, be warned.
Check the www. for "wufi", a calculation tool.
I would be interested to know where I can find out more about the EU regulations regarding calculation of dew point. Thanks.
@ suegreenbuilding:
The relevant EU standard for surface condensation is called EN 13788
It is also an international standard, EN ISO 13788
Google also for " wufi " or " wufi+ ", there are plenty of resources.
It regulates the dynamic calculation of moisture behaviour in building components, for example in walls.
"Dynamic" in this case means that the moisture behaviour/movement is calculated under changing conditions like for example changing temperatures between day and night.
And as well under changing local climatic conditions.
The outdated calculations were based on the assumption that the external influences stay static, for example they used the average temperature and not the dynamically changing temperature between day and night.
Other factors like occupier's behaviour is dynamic as well, having a shower would increase the moisture in the bathroom rapidly and slowly decreasing when ventilating.
The outdated standard took only an average moisture content for the bathroom into consideration.....
The dynamic calculation is more relyable. Therefore it is now international and EU standard.
I'm not sure if this is already translated into BS. I doubt it, but it could be so.
If you find the relevant old BS changed into the new EN ISO standard let us know, I'm also intersted in the issue.
Thanks, and good luck!
See also here:
as well as
Look there for " P 125 " to see the various relevant and legally possible calculation tools.

Is the dampness, A. at high and low levels on the inner face of the outside walls or, B. just at lower levels above the skirting board?
Is the problem restricted to outer walls where there is wind driven rain. Is the floor level of the house close to the outside ground level? Is the cavity free of debris up to dampcourse? A thorough inspection of the cavity is needed to understand what is happening.
Asssumming that the material used to fill the cavity is the cause of the problem.
1. Is this due to water migrating from the outer leaf across the cavity and into the inner leaf?
2. or is it due to dampness below the dampcourse rising up the cavity fill (or debris in the cavity) and wetting the wall above the dampcourse.
If the cause is 1. above, then assumming no problem due to defects in roof, gutters and downpipes then treating with a water repellant is likey to be a long term solution to water penetrating the outer leaf. In my experience in severe weather situations one application is still effective after 20 years. I would do this rather that repointing because it is simple, very effective and cheap.
If the cause was 2. above and the dampcourse is sound a void needs to be created in the cavity so as to expose the dampcourse in both the inner and outer walls. This can be very difficult in the absence of cellars or a workable space beneath the ground floor.

I have been having a problem with my walls and dampness too.
We moved into our home in March 2006. It had had Cavity Wall Insulation (mineral wool) installed in 2000 by the previous owner. Despite having a full survey done the problem was not picked up when we bought our house.
We 'stretched' ourselves financially to buy the property so decided to put up with the dodgy decor until we have saved up some dosh. This summer we ripped out some old kitchen units and the full extent of the problem was revealed in all its glory.
Find your guarantee. The company who installed my insulation was dissolved in 2004 so I can't get them to come back. I finally managed to get CIGA (Cavity Insulation Guarantee Agency) to respond to my pleas. They arranged for an inspection to be carried out by the system designer (the people who make the mineral wool). The man who came said the house was not suitable for cavity wall insulation and that it should never have been put in. It all needs to come out. Our bricks are porous with lime mortar (c.1910), so the damp is able to penetrate all the way through to the inner face. It is now working its way along internal walls made of the same brick. Paint is flaking, skirting boards are curling up....I am thoroughly miserable.
I have had nothing in writing from CIGA yet to say whether we are covered under the guarantee, although they are getting quotes for removal for me.
I am hoping that my matter will be resolved without the need for me to appear on BBC Watchdog!
Has the lime mortar been pointed over with cement mortar?
Are there any leaking gutters or down pipes or high ground levels?
With real lime mortar I wouldn't expect to see any problems with damp so please check this one out.
My advice re-point outside with lime mortar and the problem will go away
Yes the lime mortar has been pointed over in places with cement, but in patches and this does not correspond with the damp areas.
No, no leaking gutters, no loose or missing roof slates, etc.
Ground level is not high. This is NOT rising damp - it is occuring in patches, some of which are at downstairs ceiling height and some are half way up a first floor bedroom wall. It is penetrating damp caused by driven rain on porous brickwork.
We intend to repoint after the insulation is removed. No point doing it before because they have to remove a number of bricks to remove the insulation.
The problem is that because the edwardian bricks are porous the damp is able to bridge the cavity to the inner skin and now it is soaking into interior walls causing damage to finishes on these as well as the external walls.
The insulation is saturated - you can literally wring water from the insulation. It has to come out.
fascinated to find this forum post.
My mum had cavity wall insulation installed last summer as part of a government grant.
At the end of sept, mould exploded in one room. It has damaged the decor, furniture in that room, carpets, everything. When i say exploded, in a matter of a few weeks it had covered one wall, spread accross the curtains, all over the furniture.
She initially contacted the installer. They have never really acknowledged a problem. They did come back and put some extra cavity wall insulation on the wall affected.
They then came back and installed air bricks. This has stabalised the mould, but her house is now freezing. They will not accept liability, and have offered to redecorate and pay £250 for the trouble. Its a joke. 'Experts' from the insulation manufacterer have been out, and offered one explanation. 2 different surveyors have been, offering two different explanations. My mum is stuck between all these 'experts', who cannot agree. she is 67 years old and this is really affecting her health. We are now at the point where they are offering to remove the insulation, which she is going to take.
One thing I think we can prove is that they never did a proper survey. My question is, do they have to? Is there any legislation? she has been messed around by these cowboys no end, and its a disgrace. Can anyone offer any advice on what survey they have to do, because its clear to me they didn't do one. one of the surveyors have written this in their report.
Apologies for hijacking the post..
They are supposed to do a proper survey. If they do not, they must rectify the problems. If you can't get any joy from the installers this is where CIGA come in. You should have a CIGA guarantee. They will rectify the problems up to a value of £10000.
My CIGA guarantee states that I am covered for '"defects in materials or workmanship in connection with the installation by the Installer of the cavity wall insulation at the above property shall be recitified without charge subject to compliance with the terms and conditions set out below." Failing to do an adequate survey as part of the installation process sounds like a defect in workmanship to me.
My concern is that having had wet insulation in place for several years the cost of removal of insulation, replastering, redecoration and potentially work on the cavity wall ties (which may have been compromised) may come to more than this £10000 sum.
Thanks for the response.
I waiting on a copy of their documentation with regards to the installation. I'll post when I know more. Thanks again
I would be interested to know how you get on and be pleased to offer the benefit of my experiences if this is helpful to you or anyone else suffering problems with CWI.
We are in the process of purchasing a property and have just had the survey done. Our surveyor has picked up that there is damp in the cavity due to the cavity wall insulation (foam). He says that the only way to resolve it is to take the outer wall off hack the foam away and re-build. Has anyone had this happen to them? Can anyone give me an idea of what costs would be involved? We still want to buy the house, but obviosly want to renegotiate the price, and any negotiation would be based on what the cost of the remedial work would be.
We are going to ask if they have a guarantee of course, and may be we can get some of cost covered there, but as Crutess above has indicated, it could cost more than £10000.
Any advice would be much appreciated.
Phil Ward
How does the surveyor know that the cavity insulation is the cause of the damp?
Are the gutters or any internal leaking, is it condensation?
What is the exposure like, condition of the wall, does the roof leak?
Great to find this exchange. My mum lives in a ground floor flat of an Edwardian house, which has 4 floors in total. Her bedroom had a fireplace which has been bricked up, but the hearth and chimney flue still exist behind the brick wall. There is also an air vent into the bedroom and both alcoves either side of the chimney breast have built in wardrobes. There are no signs of condensation or damp coming through the old chimney breast.
The only place for the bed to go is in front of the old chimney breast. The problem is that cold air in the chimney and cavity makes the bricked up wall freezing and the cold air coming into the room through the vent is also freezing. My mum is 70 years old and she wakes up cold and feeling unwell every morning. It's a nightmare.
What solutions are there? Could we:
(1) brick up the hearth so there is no cold air in the bottom section of the chimney flue/hearth?
(2) fill the cavity with insulation, if so what type?
(3) fill the cavity with vermiculite - someone mentioned this to me but am not sure what it is? or
(4) does anyone have any other solutions to suggest?
I am desperate to find a solution so await any ideas. Thanks so much! and apologies also for hijacking this site/trail of communication but I am hoping there will be someone out there who can help,
You are better off investing in a proper building survey. An eengineer together with an energy advisor would be more able to sort you out.
All major building jobs should not be done whilest people are living in the structure, esp. when we look at the elderly, fragile.
An old chimney which isn't used anymore should be removed. Meanining demolished in the attic down to the level of the habitated place, maybe even further down.
The roof/attic being sealed and properly insulated.
The remaining chimney can be used as a "thermally activated" part of the structure.Check the www what this means and involves.
All these are major projects, nothing for the unexperienced DIYer. Get a professional in to write you a report of what needs to be done step for step.
They are supposed to do a borescopic examination of the cavity,the cavity has to be more 50mm or wider and they should check for damp, poor pointing and whether the property is in an exposed position likely to get driven rain etc.
I think a major problem is that the so called "surveyors" recieve very minimal training, often only a day. In addition many work on a commission based earnings meaning that if they don't find a roof to insulate or a cavity to fill then they don't get paid or recieve a minimum basic income.
I wish this forum would email when a reply is posted.
Ok quick update , CIGA have been out twice now . They basically say the house was suitable and the installation is fine.
The dampness is caused by water getting in the roof or what ever.
There probably is water coming down the cavity but its the CWI that's bridging the gap.
CIGA are a joke , you'll be lucky to get them to pay for anything a few google searches and people have taken them to court over a number of years.
We'll basically have to stump up the cash to remove it, looks like it will cost around £1200....
Don't give up that easily. Contact a lawyer, a solicitor, the consumers organisation ect..
A total removal of the fibres will be difficult, almost impossible.
Get an expertise done by an independant specialist. Since it is almost certainly that the cavity fill is the cause of the dampness problem you should be able to reclaim costs and compensation for the troubles, if not from the installer than from the insurance.
Get an architecture/civil engineering company to look at the matter.
Sometimes the problem can be identified without site visit at relative low cost, using the wufi/wufi+ program.
Condensation risks can be calculated using internationally recognised mathematical methods. If wufi says "yes, there is a risk" then it would be very, very difficult for the insurance/installer to prove the opposite.
Like claiming the laws of physics don't exist in the building world.
You wouldn't need to drill open the wall if basic calculations say already that the structure is doomed to fail.
Try your architect/civil engineering chamber for a wufi report, it is quite common in GB that this calculation method is ready available in the office.
The architecture office of J.Little/Ireland has done several calculation runs using wufi, the result is almost all the time that retrofit insulated walls will become wet
if no aditional external meassurements are taken as well. For example external cladding, water-proofing of the external wall with chemicals ect..
The problem in our climate is two fold: high relative humidity plus driving rain. The walls get faster wet than they can dry naturally.
And this will cause inevitable dampness.
The original, old cavity wall was build to avoid the soaking of the inner wall caused by driving rain. The VENTILATED cavity to dry out condensation.
Any filling of such a structure can cause dampness trouble. Therefore the company who does so is reliable for the demage caused. The usual 2 year minimum consumer guarantee is not relevant if the job wasn't suitable from the beginning. You propably have an eternal come-back to them.
But contact a legal professional about this, a certified user of wufi as well.
It propably takes only a letter from each of them (the solicitor and the architect) to get your demage covered.
An easy and relative cheap step to get these forwarded.
Good luck!
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