Damp

[a.n.other]

I have a few damp patches on my front wall. What is best, seal the inside, seal the outside, or seal inside and outside?

[a.n.other]

That is the front wall of the house, not the garden!

[Andrew Barnes]

The best thing to do is to try and find the cause of the damp, maybe a leaking gutter/downpipe etc. Sealing the wall is treating the symptoms. Is the damp visible inside or outside the house?

[Blueyonder]

Would it not be better to find out where the damp is coming from first, and tackle the problem from there?

[Gilbert]

Without tackling the source you only seal in the damp to create worse problems later. As already suggested, check the guttering/downpipes near the damp patches. Has the outside wall been rendered 'across' the DPM? This can allow rising damp to 'jump' the DPC and carry on up the wall. Is there anything against the outside wall which will cause damp - a heap of sand, a pile of bricks, a lean-to, flower bed, etc.? Is there an open chimney? Has the wall had a DPC repaired and not been re-rendered? Old damp render and plaster should be removed to a metre above the line of damp and reinstated with waterproof rendering to allow the wall to dry out without affecting any new internal plaster. Old plaster forms hygroscopic (water-attracting) salts which continue to absorb moisture from the air even if the source of damp has been cut off so it should always be removed rather than just 'sealed'. Cheers Gilbert

[a.n.other]

[Gilbert]

Check to see if the downpipe is blocked at the top outlet (where it joins the gutter) - usually with leaves, etc. This will cause water to run down the outside of the pipe, or on the wall itself. Check that any downpipe unions are sealed and/or fitted correctly (i.e. upper fits inside lower). Cheers Gilbert

[stuart]