I recently purchased a property which appeared to have some puzzling damp on the 9inch wall between the dining room and kitchen. I have been advised by a neighbour that the previous owner removed the step down into the kitchen by raised the existing kitchen concrete floor to the dining level by filling with more concrete - thereby bridging the dpc.
I plan to angle grind a gap between the new concrete and the wall - which can be covered by the skirting board. With the source of the problem solved I plan to inject walls with damp proof cream and get walls plastered.
Does anyone have any comments about the method and do damp proof creams really work if injected by an amateur. . .
Actually thinking about the whole problem again - If it had been built correctly in the first place the wall dpc would have connected with the dpm of the old floor and it wouldnt matter how much concrete was added to raise the floor - it should be damp free. So something doesnt make sense. Mind you it is a 1900 property so maybe no dpm in the old floor at all. I still feel the whole problem is related to the later concrete.
well you could paint the entire floor with buitumin if you want that, would resolve any damp issues on the floor if you want it covering with carpet, or laminate flooring. If your using tiles then a waterproof grout is recommended
There is no evidence of damp on the concrete kitchen floor - although it has plastic tiles which may well be glued with bitumen creating a dpm. The damp is showing on either side of the 9 inch wall between kitchen and dining room which are now at the same level.
Course - without xray eyes I cant be sure what was done to the original kitchen floor before the new (ish) concrete was added. Maybe the dpc has failed in the wall too. It may be safer to assume both problems - that is: new concrete covering dpc in wall - and dpc in wall failed. I dont want to solve one assumed problem then find the new plaster stays damp and needs replacing again because of another problem. . .
The floor is not the problem. Injection damp proof courses do not work at all. In fact they make the problem worse. Anything that seals in moisture such as bitumen paint can have devastating long term affects on your property. I would guess that the damp wall is plastered in a cement based plaster such as gypsum. Cement based products cannot breath and trap in moisture. If so remove the plaster and redo it with lime plaster. The same as it was when it was when it was first plastered 100 years ago.