What is happening to my wall?

14 Oct 2013
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United Kingdom
Hi all,

I'm struggling to resolve this issue because I am unsure who to call in the first instance.

This is a 7-8 year old house so still has NHCB warranty however with a £1000 excess hence the reason I am trying to get some steer.

As you can see by the picture, the right side of the exterior (rear) wall always looks damp and has green growth.
The otherside of the wall (Living room) has no signs of damp and I believe the same applies in the cavity as there is a light switch and I would have assumed maybe it would have tripped by now.

One thing to note is the roof (slate colour) above is flat with a raised ridge - when it rains, water sits on this ridge and does frequently drop onto this side of the wall but I see no difference between this and bricks being rained on

The only thing I have come across given it seems to start from the bottom is maybe rising damp?

Appreciate your insights in this and also who I need to call to rectify.
I have checked with immediate neighbours (same age houses) but annoyingly/strangely their living room brickwork is cladded so can't tell the state of it

Thanks in advance


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There is a single drain on the other end however that will only drain what falls onto the recessed part of the roof. Its a bug bear of mine because it can hold some water but does eventually drain. The ridge however as you can see from this picture does hold water and that usually only goes away if it evaporates or a bird drinks it!

We initially got a roofer out who seemed to say the roof was fine and what he would do is make a slight lift under the ridge to persuade the water to go back onto the roof but we did not go ahead with it until we understood more about the brickwork

Interestingly, me neighbour to the right seems to have a drain on the opposite side (so where my wall issue is) as well but only he has this and none of the other houses seem to on this street (identical houses)

Most definitely not rising damp. Look at the wall next time it rains heavily. My prediction is you will find water pooling on the wide steel coping and running off the edge, down the wall.
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Is that an in-use boiler flue terminal at the top of the first pic? If so, perhaps condensation from the combustion products is falling on the wall. That might also be why some of the mortar looks discoloured/dissolved.
Is that a gap below the steel coping and above the brick next to the camera? IF so, does water come out of that gap hen it rains?
Thanks all
@jeds I did take a video so I will try and hunt this down. When you say wide steel coping, do you mean they grey bit above the gap pointed out in the image by @pcaouolte ? No idea what is under it but what you see is not steel. Its the same material the rest of the roof is lined with and is fairly flexible in that it can move when you grab it - however from memory, you are right, it pools and then runs off the edge.

But why is this an issue ? Is it no different to the wall being rained on ?

@Alec_t CCTV Camera :)

@pcaouolte It certainly is a gap. I'll try and climb up probably Thursday as I've run out of light today and out tomorrow but fairly certain it is. However I can't say I remember water coming out of there when it rains. Again will check once I find the video I recorded during the heavy rain a few months back

I'm also fairly certain the mortar is quite soft in that patch - even when it has not rained for days like this week
So the little wall around the roof looks to be about 3x courses high, and the damp starts from about 4 courses down and spreads out (the white is salts carried out by moisture)...
no expert but my thoughts
assuming the water is pooling on the roof above that area, somehow it is finding its way through the brick into the cavity and directed to the outer wall i assume via solid insulation appearing where you see it
now in my mind there will be some possibly most travelling internally on the cavity until hitting the slab and finding a path to exit possibly causing the dark patch on the rhs off that vent at the wall base below the discolouration ???
The last 2 posters are onto something when i look at this. The common threads are water is pooling on the roof and drainage is poor - only one small outlet opposite end. Fall "may" be inadequate too.

The damp appears about level with the base level of the main flat roof. Ignore the parapet coping wrap for the moment if it is sound, as damp only starts beneath the extended parapet upstand.

The rigld insulation in cavity (if installed) must be protecting inside wall from damp. Have you checked it with a moisture meter?

Looks like a flat roof fault and workmanship issue to me.
Thank you all

So I think if the general consensus is the roof, I'll get a roofer in
I did contact a number of roofers with only one actually turning up quoting the following

Supply and install UPVC roof drips to the rear flat roof edge.
Materials £240.00/ Labour £225.00

I suppose at this point I'm unsure whether this is what is required or a full rework on the flat roof

From what I gather, the above quote was explained in that he had some sort of rigid material to add to the surround of that roof coping to draw the water away from the wall.
But this would not resolve the pooling on the flat raised part of the roof
Correct I don't think that is the underlying fault. You could try it. It is low cost. Not sure how they will be attaching that to the current flexible roof material up and over the copings. Hopefully some sealant and not mechanical fixing. Looks like the roof may be epdm.

But is that damp coming from the outside of the wall or the inside. That is key. You could pay for a surveyor to report but will no doubt cost similar to your excess.

Bricks facing south or south west like at our house get regularly soaked and dry out. But they don't look like that and why not to the otherside of the door return?

If it is the main flat roof structure. And there are issues with drainage exit or fall, It may all need reworking to do it properly.

Edit. But if you start fixing the roof without reference to the building or the warranty company, it maybe even more difficult to progress a claim than their fine print probably already is...

Edit edit. The other thing that definitely needs inspecting is the roofing material covering the top of parapet. Conditon, flatness, joins substructure. As you say water pools there. It doesn't sound very well finished. Not sure what they've got finishing the parapet underneath the roof covering but if it drips in there it may not show until it hits the rigid board insulation inside the cavity.
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Thank you @GoodDIYjob
Out of interest, do you work with roofing and bookable/hireable ?

As for warranty - the excess is £1000 and a lot of the delay initially was due to them as they need 3 quotes. I contacted around 20 roofers via checkatrade and only one person attended and he quoted the above which due to the value, was not worth going through NHCB obviously. They eventually closed the case because of the time it took.

They seem to be fine and even made a point that if it was below the excess, not to go through them/just get it done but its a valid point.
I've only got 2 years left on NHBC so I'm not too fussed and could just treat it as a normal wear and tear repair though I just wish I picked this up when I first noticed the brick staining.

The white "salt" as has been mentioned above I always thought was dried up foam from my washing the car (I use a foam gun). It's rare for that side of the wall to ever be hit or even any wall but I know years ago when I first got the foam gun, it splashed a bit on it.
Just being naïve I think!

Drainage - a number of neighbours have always said even during the first 2 years of the warranty (no excess, on-site repairs) but the developer maintained it was fine because water goes towards the drain. And to be fair water on the flat structure itself does go towards - its just the pooling on the ridge that sits there.

Attaching - I'm 99% sure he had mentioned sealant

Damp: Must be outside surely?
From memory of the build, I think it is brick > breeze block > cavity > plaster
Plaster side is still the original paint from when we moved in and there are no issues at all on the paint/plaster work
I don't work in roofing but I had a problem with my own flat roof on new extension. Took nearly 2 years to resolve. I had to engage a retired friend who used to own a roofing merchant and a repair refurbishment division.

Yeah, it's hard with trades especially when they don't see something glaringly obvious or they've got lots of other jobs and assume they are being asked to quote on a small £200 job that could still go wrong, not fix the issue.

It won't be a cheap repair IF the roof has underlying faults and needs really starting again. I'm hypothisising because I haven't been there and you can't see all this in photos but poor fall, inadequate outlet size or position for roof area and fall, no box gutter formed to runaway water, top of parapet not properly finished and membrane sagging and pooling. You can see how if all that were true it may be start again..

Where are you BTW?

At this point I'm trying to think a way forward for you. One option would be for a quality surveyor to inspect and write a report on the flat roof and detailing and the fault. Yes it will cost but it gives you a firm reference and armed for any battle with warranty company. And comeback with his own profession and insurance or indemnities as well...

Other choice would be finding a trusted builder who could inspect and write their own report or engage a Roofer with whom they work to report and investigate but very hit and miss without a recommendation and it is a hassle type job!

3rd choice is finding a very thorough and experienced Roofer and do the above direct but a very tricky situation to follow that through, as you've found.

More i think about it the more i think you need a independent professional with experience and their own insurance to report on the roof quality and finish.

That's what immediately springs to my mind.
I think Jeds mentioned above it is probably water running off the top of the parapet wall.

Carefully pour some water on the parapet and see which direction it runs. I suspect it will follow the path of the yellow arrows channelling it towards the corner. Or the parapet is flat and the corner is a low spot so that is where the water runs off.

Where the roof membrane has been dressed up over the top of the parapet it should really fall back (slope) towards the roof so any rainwater run off collects on the roof. If it falls the other way there is no drip detail/overhang on the edge of the roof membrane so the water just runs down the wall causing the staining and moss growth.

Roof (1) edit.jpg
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