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Fixing Penetrating Damp in the Winter

Postby Ian Dudley » Fri Dec 05, 2008 11:51 am

I moved into our house over the summer, it's a detached two story house built circa 1920.

Over the last month we noticed a lot of damp and black mold on the inside of the bedroom cupboards at the back of the house, the back of which are an exterior wall either side of an inactive chimney breast.

From investigation, the render on the chimney above the roof is falling off and needs a complete overhaul, but we're struggling with money right now and I'm not sure when I'll be able to pay the couple of grand needed to get a contractor in. I'm thinking of maybe wrapping it in a tarp until next summer and getting the work done then.

I'm also not convinced this is the sole source of damp. The damp and mold showing inside the wall is not adjacent to the chimney, but rather at the 'far side' of those sections of wall with clear dry sections between them and the chimney.

I've already discovered that the gutters on that side were completely blocked (full to the brim with soil and grass growing in them!) and have cleared them out. But I'm not convinced that was the problem either as the gutters are old iron ones that abut flush to the facia and it looks like the water was spilling over outwards. The damp areas are a few feet below the gutter.

While up the ladder I could see that there were moldy areas on the outside of the wall that match the location of the damp on the inside. The surface coating in these areas is brittle and has risen away from the wall, so I'm guessing water is penetrating through from the outside. However, the damp patches on the outside are about a quarter the size of the patch inside horizontally, although I think they are taller (its hard to directly compare). The worst area on the outside is the corner of the house and the patch on the outside runs up the corner edge for about six feet vertically around a foot or so wide.

The front corner of the house has a similar problem with a discoloured section of brittle render on the corner and we've now noticed some damp coming in at the bedroom at that end too, but there's no chimney around there.

I'm tempted to chip off all the brittle surface on the outside wall, then go over it it with exterior paint (e.g. Weathershield) or similar. Is this enough though or do I need to treat the wall first? Would it work as a stopgap solution till next summer when I can do a better job in dry weather? Or would it make the eventual correct fix even harder?

Also, do the walls need to be thoroughly dried out first? If so how do I achieve this in the winter when its never really warm enough to dry out. The wall is very exposed (the neighbouring house is shorter and lower than ours) so I guess it gets a lot of wind blown rain.

Any advice or pointers appreciated. It looks like the weather is going to be reasonable this weekend, so I'm hoping to get up the ladder and halt the problem while I can. I know there is no point in trying to address the damp inside until I stop the water getting in, and I'm worried about the black mold affecting us sleeping in the same room, not to mention its in my wife's wardrobe and she can't hang her clothes up!

Thanks in advance, Ian.
Ian Dudley
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