We have just purchased our first house (hooray) and uncovered a few gremlins the home buyers report failed to pick-up.
There was some damp on the wall behind a sofa in one room (which failed to get noticed by surveyor) and in the corner of the same room.
We had a damp expert visit and hack-away at the plaster, apply DPC, lay a water-proof paste (bitchumin). Wait 1 week to dry then plaster over.
However the problem lies in the corner of the room (external wall) where moisture is still visible, almost forming where the DPC injections were placed.
Now i'm not sure whether this is the silicone of the DPC seeping through onto the painted surface, or whether damp/rainwater is slowly still seeping in from the corner (the damp in the corner was mild before).
Any advice is appreciated!
HP
Photo below
Best Answer
DPC is a water-impermeable horizontal layer, typically a type of plastic sheet, that you would find between two courses of masonry at the foot of a wall above outside ground level (e.g. one or two bricks above outside ground level). Its job is to prevent water rising by capillary action through the masonry etc from the wet ground below.
Obviously if the DPC is damaged or defective, it is usually not feasible to demolish the wall to rectify the DPC, so there are treatments which inject waterproofing material into the wall.
I am surprised that a vertical section of the wall corner has been treated - but I've not had this problem so can't be sure that is abnormal.
If that is an external corner, I would go outside and check that there is nothing outside bridging the DPC - like a heap of earth against the wall.
I would buy a damp test meter to determine if the discolouration is due to damp.
If it is the damp expert's treatment leaching through - and he didn't warn you this was likely - I'd consider asking them for advice and/or to rectify the problem.