I'm renovating an old French farm house, which is suffering from bad damp in some walls. The walls are a good 1m or more thick at the base, made from random stone with a mud motar(!) - no DPC of course. When I got the place, the walls were not rendered inside or out, and the room in question had a mud floor. The builder didn't like the look of the outside surface of the wall, and recommended that outside we rendered with a lime mortar, to stabilize them. This was done, and a nice coat of Dulux Weather Shield was applied. In side, the dirt floor was dug out, a damp-proof membrane put down and a concrete floor poured. The builder did mention that when the floor was dug out (before the membrane & concrete went down), after several days of heavy rain there was a small lake in the room! Anyway, its been several years now since this was done (project has been on hold - fell out with the builder big time). But now I see that the internal surfaces of the stone walls are wringing wet, up to a height of about 1.5m. Lots of efflorescent salts on the surface.
My guess is that we suffer from a high water table (the internal lake when it rained), and the water is rising up the mud motar like a wick. The external render/paint job probably made it worse (preventing the wall from breathing), so its all coming in on the inside. So the question is how to solve this? We ran two 'french drains' down the outside of two sides of the house, and those walls seem a little better. Would one down this remaining wall help? If not, how do get a damp proof layer into a 1m+ thick stone wall? I'm told chemical injection wont have a prayer, and I see mixed reviews of the Dutch, or Holland, method of ceramic tubes. Does anyone have any advice?
Thanks for the advice. That's very interesting! I had heard of the system, but saw mixed reviews on the web (some very scathing). But I got the impression people were using it on brick walls, not stone ones, (where it may not be so good) and in cases where it was not a genuine rising damp problem. Anyway, its good to know that it does actually work! I'll look into it some more, and hopefully find a company locally who can do it for me.
I maybe a bit late as the work may have been carried out but I have only just joined the forum and seen your post and thought I could help. I had a damp problem in my walls that were over a metre thick and started to panic on what damp proofing system to use. However all my miracles came with FREEZTEQ'S help. FREEZTEQ is a frozen damp course system that can be carried out by yourself on the external walls, so no need to make a mess inside, BONUS!!! All I had to do is place the FREEZTEQ packages into the freezer for 48 hours then place them into pre drilled holes into the mortor line at 110mm centres to within 25mm of the wall thickness. So all you need to carry this out is a drill, a 22mm drill bit, a domestic freezer and FREEZTEQ's packs, its that easy!!
I have not had a problem since and would recommend this sytem to anybody and a extra bonus is that it comes with a 30 year gurantee! I can't find their number at the moment but type it into google and it will come it.