Damp party wall

[burt12345]

Apologies if this question has been answered before, but as we most problems, it's hard to know if someone else's issue is the same.

We have damp on a party internal brick wall (our side is most probably a extension, neighbour is most probably sandstone). So I thought I'd best strip it back and have a look, here's what I found:

1. Pulled off plasterboard.
2. Behind that, batons nailed to the wall, behind those, plastic sheet, then plaster top coat, with bonding plaster first coat, then bricks.

I have a moisture meter, and the dampness seems to rise up to about 1.5m, some of plaster has/is coming off the bricks.

Here's what I think I should be doing, could somebody please confirm this is good practice

1. Pull off any loose plaster from the bricks
2. Fill any holes and make good any areas with bonding plaster (do I need a top coat?)
3. Paint over with bituminous paint.
4. New batons 1" x 1/4" (screwed into siliconed holes or just nailed?)
5. Plastic vapour barrier
6. New Plaster board starting about 1" up the wall to leave a gap at the bottom?

Do I need to be using insulation backed plaster board? Ideally I don't want to lose any more room width than I have to.

many thanks

Matt

[burt12345]

I'm thinking that whatever I do my side will have to be a tanking measure. The dampness is pretty much the whole of the wall, so I'm guessing that the moisture is coming from the neighbours sandstone side.

Any opinions?

[stoneyboy]

burt12345,
If the damp is rising to about 1.5m then you should start by getting a damp proof course injected into the party wall.
end

[burt12345]

Is there any point doing that as I expect it's coming from my neighbours sandstone wall, would that explain why it's so high? I doubt my neighbour would do anything about it as his side of this wall is his upstairs, below that is his kitchen which is mostly below our garden level. Basically our house is basement+2 storeys at the front, 2 storeys at the back, neighbour is two storeys starting at same level as our basement.

Actually, thinking about it, the damp top level corresponds with his pitch roof line, which we've just gone halfs putting proper lead flashing between our wall and his roof. I was horrified to keep looking at the cracked concrete fillet painted with waterseal being left as a solution, so hopefully that may have been the issue? Any thoughts? I'm guessing if the wall has had years of leaking from above it will take a long time to dry out?

Thanks matt

[welsh brickie]

hack off the loose stuff, screw battens to the wall but pack them off about 10mm then sprayfoam the entire wall, The foam is waterproof so it eliminates the need for buitumin paint and vapour barrier and it will be more heat efficient.