Cause of damp issues?

DougMLancs

We’re about to complete on purchasing a 1950’s semi with filled cavity walls (filled 2011) and that has been vacant for at least 9 months. It used to have a suspended timber floor downstairs but it rotted away and was replaced with a concrete slab sometime before 2006 when the previous owner purchased it. Pebbledash to the front and rear and just brick to the side.

The driveway has been built butting up to the dpc on the side elevation do we know that will likely be bridging the DPC. To the rear surveyors can’t decide if it’s the patio being too high or the render too low that’s bridging the DPC (see photo). The DPC at the front is clear of the ground level.

We know from the building surveyor that the property has high exterior/interior damp meter readings on the 3 external walls (taken this summer). Internally there are a few places where wallpaper is peeling at the skirting level and it’s all been repainted recently so no other obvious evidence remains.

Needless to say there are those that have quoted to strip plaster to 1m and inject DPC but we’re very skeptical of this. They also want to install a soak away down the length of the side and rear elevations which I can see the merit of but I wanted to ask if there are any other entry points we should be thinking of? 

Since the original damp issues predate the CWI then we’re minded to think that it’s not the root cause but it may not be helping if it has taken in moisture. There’s a few screw holes that need filling on all three walls but otherwise pointing/render is in good condition. I’ll take more pics on the way home this evening.

FreeBear

Cut the slabs back so that you have a gap between them and the wall of 150-200mm wide. Dig down ~150mm, and then fill with decorative gravel so that it finish with the bottom of the slabs. That should stop water splashing up against the wall when it rains and limit any penetrating damp. Those are big heavy utility slabs (probably 50mm thick), so you might want to pay someone to cut them with a petrol powered Stihl saw.

The damp internally is most likely down to a lack of heating & ventilation if it has been standing unoccupied for any length of time. Open a few windows and monitor humidity levels - A dehumidifier (with the windows shut) will help dry the place out if natural ventilation is taking too long. And you are right to be skeptical of damp treatments. They invariably cause more problems and fail to cure the underlying issue.... e.g. https://forums.moneysavingexpert.com/discussion/6385858/tanking-slurry-done-wrong-advice 

DougMLancs

Thanks FreeBear! That’s a weekend sorted for me and some tools then  We’ll get our dehumidifier in there and see what it’s like after a few months.