Thermal plasterboarding solid wall/internal insulation - advice please

[Kocher]

Hi,

First time posting here, I have taken all the plaster off on the external solid 9" walls (1930s house) and now want to insulate and redo them using celotex 37.5mm thick 2.4mx1.2m plasterboards. I have heard many stories about damp and condensation issues caused by internal insulation. Do you guys think think with above, my walls could suffer from damp and condensation issues?

The walls are completely dry but it seems like the existing brick jointing material is plaster or just sand, as it starts to come off as soon as you poke it with anything, so I have removed some of the jointing and will repoint with cement mortar before adding the plasterboards. Aslo, the only issue I have with the wall, is on the plastered (maby non breathable) outside walls of a previous walking wardrop (1.5m*1.5m) in the main bedroom, they have a lot of damp patches on them and condensation too. I have had the small windows open in that room for the past 3 months and the damp patches are still there. Condensation drys off when all the windows are opened up after few hours.

I would prefer external insulation but that's out of my budget currently.

Your advice is appreciated.

 

[foxhole]

Insulation does not cause condensation in any form , must be listening to jakanory? Would use 50mm + insulted board 37 is a bit mean.

Whats on the exterior of the damp area?

 

[Kocher]

Just bare bricks. Although I did forgot to add that, the roof has some holes in it that hasn't been touched for years (I found this thanks to google streets view history) also a roofer told me the gutters need changing too as they are the old cast iron ones (all pending repairs). I have bought the house 3-4 months ago.

The 50mm is too thick and expensive, it will almost cost double the 37.5mm. The internal insulation is a short term solution and will externally insulate it in the future. Thanks

 

[foxhole]

The roof and gutters could be the source of all your damp, need fixing before any internal work.

 

[Mechanical Mike]

I insulated my walls using similar method and room was much more comfortable. Suggest use expanding foam to close any gaps and foil tape so that warm air can't get past insulation to the cold wall and condense.

 

[Spudgun888]

Insulation does not cause condensation in any form , must be listening to jakanory? Would use 50mm + insulted board 37 is a bit mean.

Whats on the exterior of the damp area?

It will if warm, most air gets behind the insulation and onto the cold wall.

 

[foxhole]

It will if warm, most air gets behind the insulation and onto the cold wall.

No air moist or otherwise gets behind insulation, there should be no gap.

 

[Spudgun888]

No air moist or otherwise gets behind insulation, there should be no gap.

Yup, if done properly, and there's absolutely no gap at perimeter, ceiling, or floor.

 

[foxhole]

Yup, if done properly, and there's absolutely no gap at perimeter, ceiling, or floor.

So you contradict yourself

 

[Spudgun888]

So you contradict yourself

How'd you figure that one out...? I said if warm moist air gets behind, which is what will happen if it's not done installed properly.

 

[foxhole]

How'd you figure that one out...? I said if warm moist air gets behind, which is what will happen if it's not done installed properly.

Exactly why would anyone leave a gap .There are endless if’s.

 

[Spudgun888]

Exactly why would anyone leave a gap .There are endless if’s.

Righteo, foxhole.