Dot and dab cold spot / damp?

[Guyray]

If damp find the source and fix it, it's a loft so would almost certainly be from a leak.
plasterboard insulated with celotex or similar would be impervious to damp due to the foil backing and plasterboard adhesive sticks to it fine.
Belt and braces would be to batten, and then use insulated board, as opposed to either batten and std board or insulated board and D&Das that wall appears to be cold wouldn't be a bad approach anyway. Battening with std board might still give you a cold bridge anyway and could still cause pattern staining.

Thanks Chappers. I think I'll stick to batten and insulated board. Not sure if I need to DPM paint and vcl layer too? It's marginal cost and time as the room will be recarpeted and decorated. Is that unnecessary?

 

[chappers]

with insulated board I wouldn't bother.

 

[vinn]

You might end up doing the whole lot again in 12 months time unless you or someone gets on the roof, and minutely examines both sides of the parapet, and takes pics of whats there.
If nothing else - eliminate possibilities.

With a child sleeping in that room you need to be pretty certain that you've found the cause, and that mould and slime dont start building up in the cavity behind the p/board.

 

[Guyray]

You might end up doing the whole lot again in 12 months time unless you or someone gets on the roof, and minutely examines both sides of the parapet, and takes pics of whats there.
If nothing else - eliminate possibilities.

With a child sleeping in that room you need to be pretty certain that you've found the cause, and that mould and slime dont start building up in the cavity behind the p/board.

Thanks. All copings and flaunchings have been checked and renewed. All chimneys pointed. Neighbour's parapet renderer, ours checked, sealed and all cracks filled. Flashings are in good order, no cracked tiles. Non Operational chimney vented and capped (with vented cap). Not sure what else to do up there? The lads on this site have been a great help, and I think have highlighted that we have not been ventilating the room well enough. This winter the damp spots have got worse, but the veluxs are rarely cracked and a bath is run in the en suite daily for our son (there is a fan in bathroom). All board to date is non insulated or foiled. The mortar in the party wall has lots of holes / gaps, so I really hope it's condensation and cold bridging. Plan is to repoint the brick work, possibly DPM paint, board with insulated board (50mm celotex GD5000) using minimal foam dabs.

 

[chappers]

As I said previously if you can leave the brickwork exposed for a while, particularly through some wet weather, you should be able to rule out damp/leaks.

 

[noseall]

You might end up doing the whole lot again in 12 months time unless you or someone gets on the roof.

It's cold bridging Vinn, pure and simple - look at the evidence. Why the scare stories about roof leaks?

 

[vinn]

I'm looking at the evidence, that shows damp brickwork, unventilated (or swept?) flue, & previous difficulties with a parapet and roof - lacking, are any photos of the roof arrangements.

I see thick black spot condensation accumulating on the cavity side of the p/board - this condition I've seen many times during demo, and its often accompanied with slime mould.

Children are more vulnerable to mould than adults.

My process of elimination doesn't rule out pure cold spot condensation, it merely attempts to answer the variables.

Jumping on to the bandwagon of mob views strikes me as more scary than coming to my own considered conclusions.

 

[Nige F]

Well judging by some of your considered conclusions I rather fancy Noseall and the mob. Just using my Queenly prerogative here

 

[foxhole]

From your description neighbours parapet is rendered while yours is brickwork? This will trap rainwater, should either be brickwork which dries out naturally or rendered both sides so water cannot get to the brick.

 

[rgregson1919]

Just came across this thread. I have a similar problem. Did you fix it ok in the end?

 

[mrpotato]

Its a long shot as this is quite old, but did you fix this? i have exactly the same issue in my attic. I found a hole in the felt, i patched it, but i still have a cold spot, and i think its because the plasterboard is going right against the brick work....

I was considering if i should use the moisture plasterboard, and put a layer of thermal foil between the rafters and plasterboard to fix on mine