Damp Assessment. Thermal Plasterboard

Ben1989

We had some damp assessed which is in our electrical/coat cupboard. The plaster is crumbling and there is also a patch of wet powder.

The assessor said it was purely due to that corner of the house collecting the cold. We also have an original stained glass window there which lets cold in.

He said a remedy is to take all the plaster off to brick and put up thermal plasterboard.

With that said, we're thinking of just knocking down the entire cupboard to free up space. This will obviously expose the cupboard wall into the hallway. My issue is, if we were to put up thermal plasterboard, I imagine it's much thicker than ordinary plaster/plasterboard leaving a big bump. We don't have the expense at the moment to do the whole side of the stairs. so it matches.

Does anybody have any idea how to make it match? Can a plasterer do a very gradual gradient from thick plasterboard to original plaster? Is just leaving as is and having a step the neatest way?

I hope I make sense.

TIA

Bendy_House

Will thermal p'board leave a step? Yes, at least 35mm thick (I think that's the thinnest), so you'd need to finish the join end off with something to make it look neat - not slope it down. A timber moulding of some sort?

However, if this damp is caused by what the guy says - essentially condensation from the house, because that wall is (a) cold and (b) not well ventilated, then (b) and (a) should be sorted by simply removing that cupboard.

You could then just reskim the damaged plaster, and leave insulating it until you can afford to do the whole wall - and then it'll match.

Is this an external wall? I'd have thought so...

If the cause is rising or penetrating damp, then you don't really want to cover this with insulated p'board until the issue is first resolved.

Ben1989

Thank you. Yes - he said condensation. It's the exact same (to a lesser extent however) in the box room that's directly above it. Always significantly colder.

Well, we won't be removing the cupboard fully, I should have said. The cupboard is in the front corner of the house which hardly sees sun. Yes it is an external wall corner. The actual cupboard area protrudes from the front of the house and the cupboard comes into the house about 1.5 metres. The idea is to knock it down and put a door back up etc flush with the front door so it will still be a cupboard (for electrical fuseboard) but significantly smaller. Maybe just put the thermal board in there as it'll be hidden away?

Bendy_House

Will thermal p'board transform the insulation value of that wall? Yes. Will it cure the damp issue? Probably, but maybe not fully.

This will likely remain the coolest - if not coldest - surface in the house, and - since it's inside a cupboard - also won't have much air circulating through it. Both are a recipe for condensation.

So almost certainly it'll make a huge difference, perhaps even fully sort it, but a 'stale' cupboard - especially if there are boxes and things against that wall which again prevent ventilation - you could still have some issues. If you do, the answer would likely be to ventilate the cupboard, and definitely don't pile it up with stuff - allow a good air channel across the wall.

Ben1989

Here is an image of the damp. I have removed the cupboard today

Bendy_House

The mains cable (and something else?) is coming through in that corner? And that's where the damp mostly is?

What's that fancy round thingy?

Ben1989

It’s an air filter just to help with the musty smell.

Here are some better images. The last image is the old cupboard.