Damp on walls - who to contact?

[Cartoonist]

My modernist flat roofed 1930s house has a damp problem. The wall of the front bedroom has damp which seems to be moving from the top of the wall downwards. I have had two roofers who both said that the flat roof was OK (although not sure if they both didn't really want the work.) My question is who do I call to look at this issue? I suspect it is penetrating damp caused by the Tyrolene render which was applied in the late 80s. Is is best to call a general builder or a renderer or a damp surveyor or try another roofer? To put this into context the whole house has a damp issue but the worst of it is currently in the front bedroom. Thank you.

 

[worms]

Have you ruled out a condensation issue?

 

[Cartoonist]

I think so, it is quite extreme. Although having read the Heritage House website, maybe it is.. I just don't know where to start really. From reading that I need to find a builder/renderer who will use lime render/plaster.

 

[worms]

What is the building's construction? A "modernist flat-roofed 1930's house" could well be a concrete construction, which would mean that breathable render might not be required.

You say that the whole house has a damp issue, which is why I wonder if this is a whole house humidity/insulation issue. The bedroom in question being worst, could simply be that the walls there are the coldest or, if this bedroom is in use, reflect a greater amount of water vapour overnight when the temperature differential between room and external wall is at its greatest.

You may well have a render problem, but there is a risk that a builder might happily replace your render, only for you to still have the problem!

 

[paulc]

What is the building's construction? A "modernist flat-roofed 1930's house" could well be a concrete construction, which would mean that breathable render might not be required.

You say that the whole house has a damp issue, which is why I wonder if this is a whole house humidity/insulation issue. The bedroom in question being worst, could simply be that the walls there are the coldest or, if this bedroom is in use, reflect a greater amount of water vapour overnight when the temperature differential between room and external wall is at its greatest.

Also had damp problems here in a slightly older house. Bit of an oddball construction in that the upper half is solid brick wall with a cement & roughcast render finish. One room was so bad, the plaster was falling off the walls when peeling back some old wallpaper. Ended up stripping the room back to bare brick and insulating the walls and shoving even more up between the ceiling joists. Now possibly one of the warmest rooms in the house, and no more damp or condensation.
Apart from the architrave and door, there were no period features to conserve/save, so had no qualms about doing the work.

With a 1930s flat roof, I'm going to guess there is no insulation up there, and if there is a cavity, that is also uninsulated. If that is the case, then the lack of insulation certainly isn't going to be helping.

 

[Cartoonist]

Yes, think it is a lot of things which have all now failed at the same time and don't really know where to start. The previous owners ripped out most of the 1930s features in the 70s so not much to save here either. I think a lot of issues are humidity and condensation but I also think that damp is getting in somewhere along the roofline edge. This is a chunk of brickwork that fell off when someone was removing weeds under tiles on a plinth under the wall around the roof.

 

[88v8]

....the whole house has a damp issue but the worst of it is currently in the front bedroom.

Mmm some houses were just not very well designed.
Some buildings were not well designed, Coventry cathedral for instance with its leaks.

Attempts to rectify may be a Sisyphean task.

Unless you are very attached to the house, and especially as its period features have gone, I would be inclined to rectify the visuals and put it on the market come Spring.

Let someone else tussle with it. Move on.

Ivor

 

[Cartoonist]

I think you're right!

 

[malcolm]

The corner that fell off is easy to explain. The tiles on top are letting water in and it can't get out because the plinth is covered in cement. It's spalling damage where soaking wet bricks freeze. For that a lead flashing on top of the tiles would keep the water out more effectively than tiles and cement and would be easier than making the plinth breathable.

There is some spalling in the bricks above. Maybe partly water migrating from the plinth or splash. There is no roof overhang to keep the water off and the bricks are cement pointed so can't easily dry. The cement pointing might be original from the 1930s but the water would dry better with lime pointing.

 

[Cubist]

Malcolm is right in my opinion; rain-water is getting trapped behind the render and the freeze/thaw cycle is causing the brick-work underneath, and elsewhere, to spall. In addition some of that trapped water is migrating indoors to form the descending damp you mention. All of this can be successfully remedied by a good general builder. The real challenge is finding one of those these days.

 

[Cartoonist]

Thank you. Also that wall around the roof is backed with the roofing felt that they have extended upwards. At the back they have brought the felt right over the top of the roof wall. Would that make the situation worse with the spalling on the brickwork? Anyway, I need to find a decent builder.

 

[Cubist]

Thank you. Also that wall around the roof is backed with the roofing felt that they have extended upwards. At the back they have brought the felt right over the top of the roof wall. Would that make the situation worse with the spalling on the brickwork? Anyway, I need to find a decent builder.

So.. in effect they have created a felt lined gulley behind the wall that will trap water if there is not adequate provision for it to drain away. In addition there would be a good chance that any seams between sections of felt will leak. Not likely to be a direct contributor to the spalling but it won't help either.

 

[Cartoonist]

We've got an area of ponding on the roof as well. I think I probably need a decent flat roofer to sort out the ponding and roof fall and then move on to the tiles/brick/render.

 

[Cubist]

Sounds like a plan - ponds v roofs, not good.