I'm looking for some advice. I have have recently bought a house and am doing some renovations. There were signs of damp on the party wall and going slightly around the corner to on an external wall. The damp does dry out slightly in dry spells however reappears in wet weather. I have taken up the floor boards in the area to reveal an area of concrete, below the damp area which does not extend the entire room, the concrete is also damp. The exterior of the exterior wall is showing no obvious signs of an entry point but the neighbour does have a drain which could be close to the area of damp . Also worth noting the neighbour is not showing any signs of damp. Does anybody have an idea what could be causing this? Any help would be much appreciated
Looking at the pics, the flooring looks new in that area, as does the concrete, I don't like the fact that the joists, which also looks new are supported by bits if timber wedged under them, all in all this looks to have been a problem area for some time, how deep is it under the flooring were there is no concrete, are there an air bricks in the outer walls front and rear.
Yep someone has lifted the flooring in that area (i.e cut floorboards on joist). When you purchased the house did the survey pick up any thing? looks like the old owners made a 'quick fix'. Can you supply and pictures of the exterior of the house.
Thanks for your replies. Yes the joists relatively new must have been replaced at some point (badly!). The ceiling above this area had also been replaced I believe due to a previous leak In the bathroom above however I think that this is unrelated as there are no signs of any other damp and the damp is rising up from the ground. The flooring elsewhere is approx 1m depth with open air bricks . There was a lot of debris beneath the floorboards in this area, could this be as simple as lack of air flow? I will post pics of the exterior tomorrow. Thanks again!
Hi Danyel (really?) That first photo shows what appears to be a very damp patch coming up from the floor - is that dark area currently as damp to the touch as it looks? It is almost certainly rising damp and is very likely caused by that concrete slab acting as a wick and drawing moisture out of the ground (which is usually damp, so nothing wrong there) and transferring it to the inner wall skin due to no proper damp proof course being fitted there (or possibly the DPC is below the concrete slab level so the concrete slab is bridging it.) As pointed out above, it's only a matter of time before these joists become affected by this semi-permanent dampness. You say it almost dries out in dry warm weather? That's not a real surprise as the unusual warmth simply manages to dry out the wall almost as quickly as it's being fed fresh damp from below! It's unlikely to just be simply a matter of lack of ventilation below the floor, although the much reduced depth due to the concrete coupled with the fact it's in a corner certainly doesn't help. But I doubt adding more vents down there will cure it. (Your neighb isn't affected probably because they don;t have this mysterious concrete slab on their side.) How to cure? I suspect you need a DPC fitted in between the concrete slab and the inner wall skin, and it should really be fitted below the joist level too - so that looks as though it should be installed flush with the top of the concrete slab. Or, how easily can that concrete slab be broken up? That might not be as hard as it appears, and could well be the best solution as it sorts out the likely cause. (Assuming that the concrete slab isn't some sort of foundation reinforcement - but surely not; it's too high for one thing.) (I'm assuming this house wall is made of 2 'skins' - an inner and an outer brick layer with a cavity in between?) Ok, if you don't break up and remove that slab, then you need to prevent damp from coming up that internal wall skin. There are liquid chemical DPCs you can inject, but you are much better off with a proper 'plastic' barrier like the type you lay when building a hoosie. 'All' that needs doing is for the first visible mortar line (the cement between brick courses) above the concrete slab top to be gouged out to leave a slot, and then for a plastic DPC to be slipped in and then the gap refilled with fresh mortar. This can be done in short stages, ooh, around 2' long so that the whole house doesn't fall down (slight exaggeration...). You would also continue this new DPC to a goodly couple of feet beyond where you see the damp patch, I'd have thought. Really not a major task at all. If it happens that the lowest accessible mortar line is higher than the bottom of the new joists, so that the whole joist cannot be isolated from the damp by the DPC, then the whole joist end will need encasing in a DPM so's it cannot get damp. These new joists - are they full length or just stitched-on end pieces? If the latter, can they be easily unbolted and removed to ease access to the lower wall? If not, I suspect they'll have to come out one way or another, but - again - not a big issue; just cut off the peskies and refit afterwards with a side-piece of joists to stitch them together. As suggested above, there is some dodgy work under that floor - it does all smack of DIY...
something is not right there - old floorboards, new floor timbers, levelled and propped with wedges - blockwork and overlapping poured concrete a poor DIY attempt to underpin perhaps
Exterior photos could be interesting. Mind you, it's a shared party wall, so the next would have had sinking feelings too had it been subsidence?
it's on the return external wall as well, perhaps not pinning for the party wall, but there's blocks showing on what looks (from the description) like an external wall where I'd expect to see bricks - so some addition/remedial works have been done - get a camera down the neighbours drain
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