Victorian stone house - damp treatment advice

[ChrisJ70]

Hi - first post on here, but probably many more needed ... I've recently bought a victorian stone house at an auction. The structural surveyor we used picked up some areas of dampness although nothing to cause structural problems, and the mortgage valuer also briefly mentioned the same although no work was required or restrictions put in place for the mortage. The surveyor suspects that there is probably an old slate victorian dampcourse in the stone walls although its impossible to tell.

All of the downstairs walls have a kotina polystyrene layer behind the wallpaper and quite a lot of the wallpaper is peeling off (hence being sold at auction).

I've had two damp / building preservation companies look at the property. One said just to replace the old skirting boards that had been subject to damp and then be prepared to decorate more frequently than a new house, the other has suggested injection of a silicon(?) dpc, tanking and rendering the walls up to 1.2m and then skimming over the top. Both companies picked up damp readings but it seemed to be barely going into the red on the meter just above the skirting boards and then green/yellow at about 2 feet up.

There are also signs of quite a bit of weevil around the edges of parkay flooring (that was under carpet) that I've uncovered. The parkay appears to have been laid on concrete flooring with an old bitumin sealant. There is one room downstairs with floorboards and there are no signs of rot in the joists etc.

So I'm very confused and not sure what to do for the best. I am hoping to stay in the property for quite a few years.

I scrapped off a section of the kotina today. Above the skirtings is about 6 inches of sand and cement render and then above that is plaster. Somebody has obviously tried to deal with damp in the past although probably quite a while ago. If I do just replace bits of skirting board, should I have the walls re-skimmed with plaster including over the render, or just use lining paper prior to painting. The plaster above the render seem fairly sound to me, but I'm no expert - it wasn't crumbly and didn't look obviously damp.

Thanks for any advice.

Chris

[Deleted-user-3]

difficult one to answer definitively...
skimming over the render is fine and wont increase the damp, though it may make the problem more obvious...
its perfectly possible to blend in to the existing although when youve removed the paper you may think about reskimming the whole wall...
if there is damp present then it will just soak into the lining paper..
the injection + tanking is expensive but will cure the problem if its rising damp...
when they tried to remedy the problem r.e. the new render, is it rendered to the floor? bridging the damp course? - common problem
and the concrete floor + suspended timber floor, do they both show signs of damp?
the thing is, if the house originally had timber floors throughout, then concreting the back room without piping the underfloor ventilation from the front of the house through to the back of the house will cause airflow problems and would contribute to the damp problem....
stone houses are notoriously difficult to treat when it comes to damp as the 'cavity' is usually just old rubble and tanking is usually the only way to be 100% sure..
the concrete floor could also be causing problems if the damp proof membrane is inadequate or non existent...
removing the damaged areas of skirting and the wallpaper will give you a better idea....
sometimes over unventilated timber floors, the gap around the edge of the floor leaks cold moist air up behind the skirting boards.... condensation forms and if left untreated will soak into the walls and skirting causing problems...
if theres no evidence of 'salts' (like a cotton wool fluff on the walls) then this may well have something to do with it...
slate dpc in a stone wall is also likely to fail over a period of many years especially with stone settlement etc so this also could be a major contributory factor...
pictures once youve removed the damaged areas would help a lot...