My Damp Hearth

Thanks guys. I had an independent damp surveyor here yesterday, and was quite surprised how he recommended to just remove the plaster from the affected walls and line with a studded DPM, dry line, and replaster. That seems to be covering up the problem rather than fixing it o_O

I had the chimney fixed about 3 weeks ago. I suppose the next step is to have the 2 disused chimney pots fitted with vented caps, as they could be letting water into the chimney behind mine (which belonged to the house next door before it was destroyed in WW2).

I've discovered the dampest area is the front corner where the chimney breast meets the flank wall. It's clearly moist compared to the rest of the subfloor. The surveyor just brushed it off as 'completely normal in houses of this age'. Argh.

I've also identified a slate DPC which is very low down - one brick above the ground in the subfloor. I suppose this makes sense as it was originally a party wall.

I wonder whether it's worth having a strip of the render removed from the outside of the flank wall and injecting a new DPC above ground level. What do people think?
 
Whilst "covering up the problem" seems daft, it's actually a standard method of dealing with the the situation. As long as the damp never rises further up the wall, then you've dealt with it in one way, rather than another. If you've found the slate DPC, then either it's failed, or the damp's coming in elsewhere. Pitting vented caps on the chimneys will let them breath, and may dry out that problem, but it sounds as though you still haven't found the source of the problem, and the surveyor saying brushing the problem off as being completely normal, still doesn't get you anywhere. I suspect you'll need to put a membrane in the floor, as well as a new silicone DPC.
 
As for digging out the hearth, I would lay in a 4" pipe which pokes out under the floor void, the other end terminates a few inches from the outside wall. Put a couple of inches of concreter mortar over it as part of the new base. The advantages are, that it will let your under floor area vent into the stack, which will keep both drier. The air vent can then go, so you are not venting hot air up the stack. If you ever get your wood burner in, you can use the vent for the fire as it will then heat the whole house.
Frank
 
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