Dampproofing Solid Walls

[andrewpreece]

My brother has an 1896 terraced cottage that has 19" solid walls. It has suffered greatly from damp in the past, caused variously by a leaky downpipe and cracked render. It took 18 months of dehumidifying to dry out the walls.

He now wants to gut the kitchen and completely refit it, and is talking about stripping all the plaster ( 3" of it ) off, and putting up some kind of dampproof membrane before having it replastered. This is because last year he found damp penetrating the kitchen wall, caused by a new crack in the render: it's all sorted now, but he doesn't want a repeat performance after the kitchen is fitted out.

To this end, he is proposing using some stuff he saw at Wickes: you paint it on as a sort of bitumastic film, then throw dry sand on it whilst it's wet to provide a key for the plaster.

Anyone used this stuff? Is it suitable for my brothers' intended use? Could it exacerbate problems if there is a penetrating damp problem again? Any insights appreciated,

cheers,

Andy.

[BigWallop]

You say the render has been put right on the external side of the walls, and I'd just like to know when the render was last replaced on this cottage, before this new rendering was applied? Did the builder use any modern forms of damp prevention on the walls before applying the new render, or was the rendering just patched in places?

Are all the pipes and drains sound? You're sure they aren't going to split and cause the same problems? Have any measures been taken to prevent any further damp ingress from other points around the property? Things like lowering the ground level slightly so the damp doesn't climb the walls. Roof drainage is all sound and checked for deterioration. Soil and grey water are being taken away from the house correctly. Things like that.

If all the preventative measures are in place to stop the dampness from re-occurring, then your brother should haven't any worries about fitting the house out inside.

[Mike]

I wouldn't do it. If you put dampproofing on the inside of the wall, damp will still gather in the wall and the only way out is through the render which will fail again.

If you really have 3" of plaster, consider instead removing this and using the space for a vented cavity behind some insulated plasterboard, fixed onto battens. Would still be about the same thickness but warmer and all damp would leave through the vents you would put in.

[N. Thornton]

Fwom:andrewpreece ( [e-mail])

This is altogether the wrong aproach. Ask the folks at

explain why, and how it can be sorted out properly.

If you do the above you'll only have more problems in future.

NT

[andrewpreece]

Thanks for that, I have reposted the query there and will see if anything turns up,

cheers,

Andy.