Currently undergoing a barn conversion - new concrete floors are in - am now considering what damp proof route to follow?
I've had a survey and a quote from a local reputable firm and they have advised the following:
Injected damp proof course and tanking system to 1.5m and return onto floor.
Personally I can't see how a pressure injected course can work in a stone wall? We want to have it done by a firm to get the cover of the warranty.
A good builder friend of mine used SBR tanking to 1.5m and has had no trouble over the last 3 years or so in his barn - even where the outside level of the garden sits about 6 inches from the sitting room window!
Research and experience indicate that damp moves through the small air bubbles entrained in mortar.
Where you have a brick wall with consistent mortar joints a dp cream inserted into a line of mortar will do the trick.
Having said that. As always it depends on the person doing the job.
For example damp proofing round chimneys can be doubtful.
For a stone wall with a rubble infill its impossible, how ever much you put in.
Consider? Its been there for a long time? What type of soil? Is it on a slope?
All these things may mean that given time 2 to three years, with the use of a dehumidifier or two and, steady heat indoors it may well dry out enough.
Traditional silicone injection won't work. Neither will the modern method of injecting creams into mortar beds. You have 2 options with a remedial dpc in this type of construction.
1. Injection mortar.
2. Electro osmosis.
It has to be put in above ground level so if you have any wall below ground level then tanking will be required. If tanking was correctly installed to a high enough point you could argue that you wouldn't need to install a new dpc as there is a limit as to how high moisture will travel up a wall particularly in a rubble filled wall which has several voids within.
Bear in mind though that moisture will travel higher if it can't evapourate. It tends to rise to the point where uptake = evapouration.
In our old stone cottage, nothing worked. We tried silicone injection, mortar injection (twice) ang 'Lectros' electric system. In the end we tanked all the walls up to ceiling height using a fantastic product called 'Spry membrane' and we have a bone dry house. The spry membrane systen allows the walls to breathe, whilst keeping out all the damp.