im a builder ..the system i use works like this ..excavate a channel around floor up to all walls ..75mm wide ..fill with pea gravel ..another channel leads to a sump with a pump ..connected to a drain ..any water entering will filter through gravel to sump where it is pumped away ...the walls are covered in a stiff plastic ribbed sheet ..this sheeting has a flat area where you drill and fix to wall .when the fixing is in place .in the centre of fixing is another fixing point ..you fit vertical 2x1 lathes to this ..then you can plasterboard ..floor similar but has upstand ..this method leaves the room totally dry ..i recently done a job using this method and the room is now full of computers .. its not cheap 7-10 grand but 100% good

The other answer is right. There are no half measures here. If you want dry walls this is going to be messy. The walls need to be cut back to the masonry the dimpled plastic put in running to some sort of soak away or best a sump pump and drain.

I have two rooms in my house which are partially built into a hillside. The far wall of the rooms is completely underground, one of the side walls connects to the neighbours (this is dry). The other side wall is an exterior wall with a small window (this is damp in a wedge shaped patch with the thick end of the wedge towards the underground wall. The dividing wall between the two rooms is damp also.

Both rooms were tanked several years ago and damp proof flooring was installed. The flooring is fine however the tanking has failed. The end, dividing and part of the exterior wall are damp. The end wall and dividing wall is also salting.

My question is; does anyone know of a damp proofing system which I can have installed which doesn't involve having the old tanking hacked off and replaced? I know this would make a huge mess and I would like to avoid it if possible.

Thanks