DIY Insulation & Plasterboard Sandwich

[Nick]

I've read of a few people using separate PIR boards and plasterboard sheets for internal wall insulation instead of buying the pre-bonded stuff. That's exactly what I'm planning to do for my retrofit as it will make the airtightness detailing a lot more solid.

 

I'm not clear on what to use to stick the plasterboard to the foil-face of the PIR though. I'm planning to use adhesive foam to stick the insulation boards to the masonry so using it again to stick the plasterboard on would make sense, but I'm not sure how much of a gap it will leave - I have a fiddly detail to line the plasterboard edges up with the windows and anything more than a couple of mm gap will be an issue.

 

Alternatively, acrylic adhesive will stick to both materials according to literature, so I'm wondering if a grid of small blobs on the plasterboard be a workable idea? The only thing thinner would be contact adhesive (or nothing and just bang a load of mechanical fixings in), but I have my doubts the insulation boards will be flat enough for either of those to work.

 

Can anyone who's done it before advise what worked for them?

[nod]

Your making hard work of it 

[Nick]

26 minutes ago, nod said:

Your making hard work of it 

 

By using separate boards?

 

I originally planned it with insulated plasterboards and would make life easier to use them, but there were just too many places that I couldn't find a way to seal properly. It's an old building where there needs to be a continuous VCL to protect the brickwork. With a pre-made board where the VCL is glued between the insulation and the plasterboard, I have nothing to run airtight membranes from windows or perimeter details into - no way to overlap them / glue them / clamp them, e.t.c. How do you go about detailing these sorts of areas if using insulated plasterboard?

[nod]

47 minutes ago, Nick said:

 

By using separate boards?

 

I originally planned it with insulated plasterboards and would make life easier to use them, but there were just too many places that I couldn't find a way to seal properly. It's an old building where there needs to be a continuous VCL to protect the brickwork. With a pre-made board where the VCL is glued between the insulation and the plasterboard, I have nothing to run airtight membranes from windows or perimeter details into - no way to overlap them / glue them / clamp them, e.t.c. How do you go about detailing these sorts of areas if using insulated plasterboard?

If you use insulated pb you can simply seal in the same way as dot and dabbing with 12 mil pb 

Continuous bands of compound 

[Nick]

19 hours ago, nod said:

If you use insulated pb you can simply seal in the same way as dot and dabbing with 12 mil pb 

Continuous bands of compound 

 

I get that the tape & fill between boards and the band of compound behind them is supposed to be airtight, but what about all the other details that aren't just one board next to the other?

 

Like when a board finishes up against an existing stud wall, or a ceiling, or a window, or a doorway, e.t.c. The way all the IWI guidelines tell it, air / vapour is just going to take that route to get to the masonry and create air leakage & condensation.

 

The only solution I can think of (the one we use in the glazing industry) is to run a membrane to continue the layer and overlap it onto the next airtight element and terminate it mechanically or with adhesive. I can see a way to do that with separate PIR boards as there is an nice foil face to stick things to, but how are you supposed to do it with insulated plasterboard where you can't access the VCL?