Patching old plaster with plasterboard

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Oops, obviously had this on the wrong forum, as got no replies.

Got a small job where I've decided to use plasterboard instead of thistle, for a few reasons actually, main one being I'm not that good at plastering& there's a residual damp issue which I don't trust not to come through again with plaster (previous attempt at plastering the bottom 10 courses of brick resulted in bad salt efflorescence - wasn't tanked though). Also, it doesn't have to be too pretty because the wall will eventually be behind a built in cupboard. I will probably attempt a finish skim coat though.

The plaster was hacked off & brickwork left to dry out for about 2 years & the only remaining sign of damp on the party wall appears to be in one small area of pointing (circled blue). Previous damp-proof rendering under the window & in the corner of the outer wall seems to have been successful. So, I'm not sure if the source of the damp is rising damp or the result of a massive leak from upstairs next door about 10yrs ago, which affected my neighbour much worse.

Just as a FYI, I will be using a salt inhibitor & KA tanking slurry (up to blue arrow level) behind the gyproc, which will be attached with Sudal foam.

So, Q1. How much gap, if any, should I leave between the edge of the plasterboard & the existing plaster on the left & above that it's going to butt up next to?

Q2. As I will eventually be removing the skirting board along the wall to the left (red arrow) (as well as beneath the window wall corner - to dotted red line) to allow the back of the cupboard to lie flush to the wall, I'm not sure what I should fill the gaps with: plaster, plasterboard or wooden plank? (those bits of wood at the bottom were just there to stop mice getting in)

Thanks guys
Damp proofing job.jpg
 
Oops, obviously had this on the wrong forum, as got no replies.

Got a small job where I've decided to use plasterboard instead of thistle, for a few reasons actually, main one being I'm not that good at plastering& there's a residual damp issue which I don't trust not to come through again with plaster (previous attempt at plastering the bottom 10 courses of brick resulted in bad salt efflorescence - wasn't tanked though). Also, it doesn't have to be too pretty because the wall will eventually be behind a built in cupboard. I will probably attempt a finish skim coat though.

The plaster was hacked off & brickwork left to dry out for about 2 years & the only remaining sign of damp on the party wall appears to be in one small area of pointing (circled blue). Previous damp-proof rendering under the window & in the corner of the outer wall seems to have been successful. So, I'm not sure if the source of the damp is rising damp or the result of a massive leak from upstairs next door about 10yrs ago, which affected my neighbour much worse.

Just as a FYI, I will be using a salt inhibitor & KA tanking slurry (up to blue arrow level) behind the gyproc, which will be attached with Sudal foam.

So, Q1. How much gap, if any, should I leave between the edge of the plasterboard & the existing plaster on the left & above that it's going to butt up next to?

Q2. As I will eventually be removing the skirting board along the wall to the left (red arrow) (as well as beneath the window wall corner - to dotted red line) to allow the back of the cupboard to lie flush to the wall, I'm not sure what I should fill the gaps with: plaster, plasterboard or wooden plank? (those bits of wood at the bottom were just there to stop mice getting in)

Thanks guys
Damp proofing job.jpg
@John j
 
Dear god...
Is it advice you want?
That all just sounds like the biggest ever bodge from a bloke who knows very very little about plastering or damp issues and wants confirmation that what he intends to do for a CUSTOMER... Is correct...
Its a no from me im afraid...
 
Oops, obviously had this on the wrong forum, as got no replies.

Got a small job where I've decided to use plasterboard instead of thistle, for a few reasons actually, main one being I'm not that good at plastering& there's a residual damp issue which I don't trust not to come through again with plaster (previous attempt at plastering the bottom 10 courses of brick resulted in bad salt efflorescence - wasn't tanked though). Also, it doesn't have to be too pretty because the wall will eventually be behind a built in cupboard. I will probably attempt a finish skim coat though.

The plaster was hacked off & brickwork left to dry out for about 2 years & the only remaining sign of damp on the party wall appears to be in one small area of pointing (circled blue). Previous damp-proof rendering under the window & in the corner of the outer wall seems to have been successful. So, I'm not sure if the source of the damp is rising damp or the result of a massive leak from upstairs next door about 10yrs ago, which affected my neighbour much worse.

Just as a FYI, I will be using a salt inhibitor & KA tanking slurry (up to blue arrow level) behind the gyproc, which will be attached with Sudal foam.

So, Q1. How much gap, if any, should I leave between the edge of the plasterboard & the existing plaster on the left & above that it's going to butt up next to?

Q2. As I will eventually be removing the skirting board along the wall to the left (red arrow) (as well as beneath the window wall corner - to dotted red line) to allow the back of the cupboard to lie flush to the wall, I'm not sure what I should fill the gaps with: plaster, plasterboard or wooden plank? (those bits of wood at the bottom were just there to stop mice getting in)

Thanks guys
Damp proofing job.jpg

Q1. A smidge.
Q2. Whatever as you won’t see it.
 
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