Baffled by Damp on Walls.

[BearTricks]

Hi.

We repainted about six months ago and noticed some damp shortly after. Prior to repainting there was none noticeable. Its all on the front wall of the living room which has a large, flat roofed, bay window. Recently with the weather it has got much worse.

Now there is an almost perfectly horizontal line of damp about three or four feet up, on both sides of the window. This would suggest something structural to me. Below that the damp is patchy with the worst spot coming out from under the window on one side. It doesn't seem to be rising damp although there are some patches by the skirting boards.

I originally thought water was collecting on top of the window, coming down the sides and penetrating however there doesn't seem to be enough to do this. Apart from where the worst patch under the window is, I think that's where the water does drip the most. The opposite side seems to get little to no rain on it but is still damp.

A friend who lives in a similar house, built at approximately the same time, is sueing a company because badly installed cavity wall insulation got damp and ruined quite a pricey renovation job so of course my other half is convinced it's that.

I don't know much about anything, but starting on the assumption that it is cavity wall, could the horizontal line be where the insulation has slumped and created a colder void where condensation could collect? I can't see any damage on the outside walls. The pointing looks fine as far as I can tell.

The house belonged to a relative and we are not sure if there actually is cavity wall insulation but it's likely if other homes like ours had it. I still can't figure out why the damp only started showing up after we painted.

Any advice would be appreciated, including on what to do next. Never had to deal with this issue before.

 

[sunnybob]

If you have a loft, you can crawl over to the edge and look into the cavity, but protect yourself from the fibreglass with a full paper suit and mask and goggles.

A long time ago now (70's), but my inlaws had exactly your problem with a new house, they tried everything but could not cure it. eventually the y broke the inside wall away where the damp was, and found the builders had completely filled the cavity in that area with broken bricks and floor sweepings. It was a biggish job to clear all the scrap out, but once repaired the damp never came back.

 

[MikeG.]

It sounds a little like this house might have had previous damp "treatment" (AKA as vandalism), including the installation of a waterproof plaster, which was/ is typically specified for a metre high. This simply masks the problem rather than dealing with it, and might explain why the damp is visible above a line at this approximate level.

Damp advice over the internet, without seeing photos or doing a site visit, is fraught with danger. As sunnybob has shown, there can be reasons for it which no-one could predict. Assessing the factors leading to damp in the first place would start with a full description of the wall, including age, condition, type of masonry, mortar (including re-pointing), and surface finishes. And of course, photos.

 

[novocaine]

you'd be able to see injection points up the outside of the wall if it has cavity insulation installed (normally looks like a random pattern of 1" cement plugs in the mortar line). you can also ring CIGA (google it) who should have a record of it if it was installed as it had to be registered.

beneath a window is unlikely to be slumped insulation unless it's got wet, I'd go with Mike's vandalism assessment, again look on the wall outside for plugs in the somewhere in the lower 5 courses this time in plastic.

I'd also add that like Mike's assessment of damp cowboys I'd consider the dopes adding cavity insulation to be in the same category of vandal.

 

[MikeG.]

......gotten.......

Don't go turning American on us!!!

 

[novocaine]

......gotten.......

Don't go turning American on us!!!

Sorry, fat fingers and fast typing. ah, I see what you mean by going Americano.

 

[BearTricks]

Think I've figured it out.

There's a small hole in the flat lead roof over the front window for the water to drain via a small drainpipe in to the main drainpipe. The small pipe is blocked so excess water is running down the wall right in the corner between the two houses where you can't see it. Alas this is where the damp is worst.

After failing to disturb the blockage with a big stick, and feeding a hosepipe out of the window to flush it out I got annoyed and climbed out on to the roof in my waterproofs with a pair of rubber gloves. Seems like there's something substantial in there (probably matted together with years of pigeon sh&#t) so I reckon I'll get a drain snake tomorrow and do it properly.

The sun is out now so hopefully no more rain overnight.

 

[Rorschach]

The smallest of holes can cause big problems over time. A pin prick hole in the welded seam of our car over the course of several months filled the spare wheel well with gallons of water and soaked all the carpets in the rear of the car.

 

[Lons]

The smallest of holes can cause big problems over time. A pin prick hole in the welded seam of our car over the course of several months filled the spare wheel well with gallons of water and soaked all the carpets in the rear of the car.

I had the same issue with a new BMW a number of years ago, wasn't noticible as the water collected in the spare wheel well under the boot cover, the car electrics eventually went haywire but it took the dealer more than a week to find and sort the problem and yes it was a couple of pin sized holes in the weld.

 

[Phil Pascoe]

Think I've figured it out.

There's a small hole in the flat lead roof over the front window for the water to drain via a small drainpipe in to the main drainpipe. The small pipe is blocked so excess water is running down the wall right in the corner between the two houses where you can't see it.

This has annoyed me, as I have see this before but didn't remember it. The lead tray when I realised where the blockage was was holding maybe 35 - 40 gallons of water.

 

[BearTricks]

Here we go again.

Could not shift the blockage so had to call a roofer. He took a few attempts to clear it, but it seems fine now. He also told me the gutters were blocked so he cleared those too. I can't actually get to the gutters and wouldn't if I could because they're so bloody high up, so had to take his word for it conveniently.

However, the damp isn't shifting.

The majority of the damp is to the left of the bay window, where most of the water was leaking. It showed up around the time we realised the roof was overflowing, and some of it seems to run down from under the windowsill so I'd be surprised if there isn't a link. It comes and goes but it's worst when the radiator, which is also under the window, is on. A few weeks ago, the drainpipe on that side of the window came loose and was pouring water down that side of the window too.

On the walls around the bay window, the damp is about a metre up in a perfect straight line, which I understand indicates waterproof plaster. The walls outside aren't wet, the pointing could be touched up in a few places but I wouldn't say it's damaged, and I can't see any indications that there's cavity wall insulation installed.

We've had some plumbers round, one to replace the valves on that radiator, and they didn't seem to think there was a leak in the system. The pressure isn't dropping, at least not at a noticeable rate, and I'd hazard a guess that it would have to be dropping enough to notice in order to cause damp.

Would it be possible that, with the roof and the bust drainpipe, water has built up in the walls and we're seeing it work it's way out via evaporation when the radiators are on? If so, would a dehumidifier speed up the process? I can't think what else it could be given the evidence, but then again I sit in an office all day every day so what do I know?

Otherwise any ideas? At times like this (and when I talk to mates who are plumbers, and when I pay triple digits to get an emergency plumber out on a Sunday evening) I wish I'd trained as a plumber myself.

 

[Inspector]

You'll probably hate me for saying this.
It's time to cut a few inspection holes in the living room plaster and have a look. If areas are wet you might want to peel enough off to find out where the water is getting in and go from there. After you get that dealt with you can decide what to do about the rest of that wall. Rip off all of the wall and clean up the damage and mould now or just patch until the summer and fix it then
Sucks that it is this time of year.
Pete

 

[novocaine]

much like drying wood. about 1" an year. (ok, bricks are a bit quicker, more like a year to dry out a wall). yes a dehumidifier would help. won't fix the world though I'm afraid.

 

[Nigel Burden]

My daughter has damp in one corner of the lounge in her flat, ex local authority old peoples flat. It is about two feet down from the ceiling. The flat behind extends beyond hers creating an L shape externally. She has had the landlords out numerous times to attempt to sort it out.

The problem fist occurred after the management company, which is basically a company set up by the old East Dorset Council, made a repair on the valley in the roof to remedy a problem that a neighbour in a flat below and behind hers was having. This gives you an idea of what she is dealing with. They, the management company, have suggested that it could be coming from the other side of the building :shock: although their surveyor believes it's the valley on the roof. They have also had plumbers out who have confirmed that there is no plumbing in that area.

After threatening legal action they are supposed to be getting roofers out today to look at the problem as the surveyor believes it's the roof

A few years ago we had a damp problem in one corner of our lounge and a little in the front of the lounge. We had the front and sides of the house re-pointed as these were the walls that were getting the prevailing weather. The pointer said that he believed that the house should not have been cavity wall insulated, it was done by the previous owners when the house was about three years old in 1977 with urea formaldehyde foam. He suggested removing the insulation and installing external air bricks to keep air flow in the cavity. We had this done, and a ventilation system installed in the loft to keep air circulating, and ten or so years on we have not had a damp problem.

I also had a problem on a previous house where it was cavity wall insulated. That was due to dirty wall ties allowing damp to wick across the cavity.

So as you've probably guessed, I'm not a great fan off cavity wall insulation, although I believe house are now built with insulating blocks on the inside wall with a gap creating a cavity.

Nigel.

 

[BearTricks]

I forgot to mention.

House built around 1890.

There's a handful of air bricks around the house. My job this evening is to go round and see if they're blocked up at all. Dehumidifier on order from Amazon.

 

[Lons]

I forgot to mention.

House built around 1890.

There's a handful of air bricks around the house. My job this evening is to go round and see if they're blocked up at all. Dehumidifier on order from Amazon.

Ah well your problem can't have anything to do with cavity insulation as it wasn't introduced until the '70s.
My son has a substantial brick terraced house with solid brick walls built around the same time and he had damp issues due to a leaking gutter / down pipe connection, it took 12 months to dry out.

 

[novocaine]

I forgot to mention.

House built around 1890.

There's a handful of air bricks around the house. My job this evening is to go round and see if they're blocked up at all. Dehumidifier on order from Amazon.

Ah well your problem can't have anything to do with cavity insulation as it wasn't introduced until the '70s.
My son has a substantial brick terraced house with solid brick walls built around the same time and he had damp issues due to a leaking gutter / down pipe connection, it took 12 months to dry out.

except in the 00s the government decided it was a great idea to offer a grant for it to be installed which had the same effect as when they did the same to combat damp, you got every schister and cowboy under the sun starting cavity insulation firms and installing (badly) cavity insulation in homes that really shouldn't have had it. there were genuine companies out there but they weren't that common.
10-15 years later and those homes are now having massive issues with damp, bridged cavities and failed wall ties.
The guarantee that was given at the time? 10 years and completely worthless. any (and I mean any) modification to the insulation and it isn't cover. so had a company come out and take a look at your damp, maybe drilled an inspection hole to see what was going on? lost your guarantee. had your windows replaced, yep it's gone. had your door replaced, yep, gone. You can appeal to the ombudsman, they'll send someone out to inspect, don't expect a response though.

it costs around 2k to remove the stuff from a 3 bedroom house.

The people taking it out? same as those that put it in but a different company name.

On a new house the cavity is maintained, the insulation has to be placed against 1 leaf with an air gap (both for how it works and to stop bridging), on an old house with injected insulation, that doesn't apply.

sorry, rant stopped.

don't think it's cavity insulation that's the issue here, think it's just drying out time if you've stemmed the leak. a brick can hold something like 1/4 litre of water, you've got a few of those sat there so call it 20 litres, add plaster to the surface and you have maybe 30-40 litres of moisture as a maximum in the wall. stick a bucket in the corner of the room with 5 litres in a see how long it takes to evaporate (granted, bigger surface area but you get the analogy) it's going to take a long time to dry out.

 

[Woody2Shoes]

I forgot to mention.

House built around 1890.

There's a handful of air bricks around the house. My job this evening is to go round and see if they're blocked up at all. Dehumidifier on order from Amazon.

Ah well your problem can't have anything to do with cavity insulation as it wasn't introduced until the '70s.
My son has a substantial brick terraced house with solid brick walls built around the same time and he had damp issues due to a leaking gutter / down pipe connection, it took 12 months to dry out.

except in the 00s the government decided it was a great idea to offer a grant for it to be installed which had the same effect as when they did the same to combat damp, you got every schister and cowboy under the sun starting cavity insulation firms and installing (badly) cavity insulation in homes that really shouldn't have had it. there were genuine companies out there but they weren't that common.
10-15 years later and those homes are now having massive issues with damp, bridged cavities and failed wall ties.
The guarantee that was given at the time? 10 years and completely worthless. any (and I mean any) modification to the insulation and it isn't cover. so had a company come out and take a look at your damp, maybe drilled an inspection hole to see what was going on? lost your guarantee. had your windows replaced, yep it's gone. had your door replaced, yep, gone. You can appeal to the ombudsman, they'll send someone out to inspect, don't expect a response though.

it costs around 2k to remove the stuff from a 3 bedroom house.

The people taking it out? same as those that put it in but a different company name.

On a new house the cavity is maintained, the insulation has to be placed against 1 leaf with an air gap (both for how it works and to stop bridging), on an old house with injected insulation, that doesn't apply.

sorry, rant stopped.

don't think it's cavity insulation that's the issue here, think it's just drying out time if you've stemmed the leak. a brick can hold something like 1/4 litre of water, you've got a few of those sat there so call it 20 litres, add plaster to the surface and you have maybe 30-40 litres of moisture as a maximum in the wall. stick a bucket in the corner of the room with 5 litres in a see how long it takes to evaporate (granted, bigger surface area but you get the analogy) it's going to take a long time to dry out.

I agree with the points about retrofitted full cavity fill insulation and about the potentially long drying out time. I think that a more salient point about a house built 100 or more years ago is that it's fairly unlikely to have a cavity at all!

 

[Lons]

a house built 100 or more years ago is that it's fairly unlikely to have a cavity at all!

I would say it's very unlikely and that the walls will be solid, one giveaway is to look at the brick pattern on the outside where if the bricks show as full side on along the length of the courses it's likely to be cavity and wall ties but if there are regular examples of bricks end on then it's solid is the bricks are used as ties.
Cavity walls didn't become widespread until around the 1920s so probably 30 years after this house was built.
How much water the bricks are holding depends on the porosity of the bricks, in my sons' case they are very dense and most of the ingress tracked through the mortar.

As far as grants for cavity insulation is concerned unfortunately it's all too common that decisions are made on all kinds of actions without enough though for the consequences or sufficient regulation to prevent abuse. Could name loads but smart meters that don't work and electric cars with not enough charging facilities are two that come to mind. I'll continue to ignore both until all the issues are solved. :wink:

Edit:
This publication might be of general interest. http://thinkhouse.org.uk/2019/nhbc1019.pdf

 

[Woody2Shoes]

There are also little traps for the unwary. I just built a cavity wall but used snapped headers to make it look like a solid wall - in flemish garden wall bond. There are also brick facades stuck old timber frame and things like mathematical tiles made to look like brick. I suppose these aren't really cavity walls but walls with voids in them! Cheers, W2S