Flyfisher
Member
- Messages
- 10,168
- Location
- Norfolk, UK
We have a room that was redecorated about 8 years ago and involved stripping all walls of all plaster and cementitious render and re-rendering with a lime mix. Unfortunately, the lime render was then skimmed with gypsum plaster (don't ask!) before being painted with F&B casein distemper. Eight years on, all is well except for one area about 1m2 where the paint has 'blown'. Interestingly, the problem is on an internal wall and not an external one, so I don't think it's a penetrating damp sort of problem.
I've been thinking the best solution is to strip back the affected area (and a bit more) to the brickwork and replaster entirely with lime and then repaint with more distemper for a nice breathable wall. However, speaking with other people I've been warned that the blown paint could be due to salts within the wall coming through the plaster and that replastering may not stop this. It was suggested that a 'salt neutraliser' applied to the brickwork before replastering might help. I'd not heard of such a thing before. Has anyone tried it? https://www.permagard.co.uk/salt-neutraliser-5-litre
Another suggestion has been to use a sulphate resisting cement render with an additional liquid salt inhibitor additive, then a skim coat of normal finishing plaster on top. Apparently this would stop the salt from coming through to the surface. but of course would also be an impermeable finish that might lead to other problems, so I've discounted that idea and my feeling is to simply remove the offending area and replaster with 2 or 3-coat lime plaster.
So my real question is about the salt neutraliser - will it do any good? Could it do any harm? Any other suggestions?
I've been thinking the best solution is to strip back the affected area (and a bit more) to the brickwork and replaster entirely with lime and then repaint with more distemper for a nice breathable wall. However, speaking with other people I've been warned that the blown paint could be due to salts within the wall coming through the plaster and that replastering may not stop this. It was suggested that a 'salt neutraliser' applied to the brickwork before replastering might help. I'd not heard of such a thing before. Has anyone tried it? https://www.permagard.co.uk/salt-neutraliser-5-litre
Another suggestion has been to use a sulphate resisting cement render with an additional liquid salt inhibitor additive, then a skim coat of normal finishing plaster on top. Apparently this would stop the salt from coming through to the surface. but of course would also be an impermeable finish that might lead to other problems, so I've discounted that idea and my feeling is to simply remove the offending area and replaster with 2 or 3-coat lime plaster.
So my real question is about the salt neutraliser - will it do any good? Could it do any harm? Any other suggestions?