best way to fix insulated plasterboard (50mm)

DublinDilbert

Hi All,

I'm going to be fixing insulated plaster board (50mm) on two external bedroom walls. I'm planning to fix with mushroom fixings and will get a plaster in, I will also use the insulating caps on the metal mushrooms.

I was going to go belt and braces and use a thin coat of bonding compound, possibly put on with a notched trowel, to also bond the board in place. Would this be considered over-kill? My thinking is that this would take up the space between the board and the wall, avoiding any air gaps etc.

Thanks.

10-10-20

Would you consider adhesive foam? I'll be using it tomorrow to fit reveals here, it's a good system. It can get tighter to the wall than dots and dabs without doing what you're describing.

As you'll probably know, dots and dabs are done so that if the background wall is out of whack then you have 2 or even 3cms of wiggle-room to even out the boards. No real reason why this can't be lessened on a very flat wall, but you need to be sure that it's flat and that your first board gets installed with sufficient clearance off the wall so that all remaining boards are able to be aligned appropriately.

One thing I'll mention is that I went down to Chadwicks today to pickup foam adhesive and their pricing was actually bonkers - they had 750ml cans for 19 to 25 EUR while you can get similar cans in other providers for 10 EUR. So shop around.

In terms of metal mushrooms, I don't see justification in fitting steel mushrooms throughout, I mix the types by fitting both nylon and also steel ones, typically keeping the steel ones to the upper parts of the board. As it has been pointed out - if the fire is hot enough to melt the nylon, you'll already be at the gates. ;)

DublinDilbert

Thanks for that. I have used foam in the past and will be using it on the reveals.

Walls are fairly flat, so was going to butter the area with a notched trowel and offer up the boards. I also find the adhesive is good to give a bit around the edges of the board,to the ceiling and other walls

DublinDilbert

BTW the reason I only use foam on the reveals is that I find it takes up all the voids and deals with them being uneven. I don't like the idea of any voids behind the boards on the wall

GreeBo

Are the walls already bare block/brick?

If you havent bought the warmboard you might consider battens with 30mm+ insulation between them, then 20mm warmboard over the top to help with thermal bridging from the battens. The benefit here is that you can fit a continuous VCL over the 30+mm and also you can fix the plasterboard (and future curtain rails, tv's etc) to the battens. The VCL will work as an air barrier and help minimise draughts behind walls/sockets etc, if you detail it well.

Downside is that you have to batten out the wall first of course! But if the walls are pretty plumb then that isnt that bad a job. Rockwool might be easier to fit between the battens as its more forgiving than PIR, which you would need to cut well and then use gapo tape or foam to fix into place.

If you go ahead with the 50mm board straight to the walls, then ensure a continuous bead of foam or adhesive around the edges to also cutdown on draughts.

DublinDilbert

I used the sticky foam to bond them, I forgot how good that stuff is, there really isn't any gap behind the boards. Did use some mushroom fixings too.

I also put some brown rawl plugs inside some mushroom fixings, so I can screw the rad brackets and skirting directly into them. I also added mushroom fixings for the curtain rail brackets, I have some small self drilling screws for metal studs, mounted the curtain rail brackets to the mushrooms.

Dr.Tom

I was always under the impression there was a proper sequence to follow when doing this in regards to fitting a membrane amongst other things to stop mould forming between the plasterboard and original wall.

GreeBo

https://www.boards.ie/discussion/comment/123099114#Comment_123099114

Yep, membrane goes on the warm side, which for us in Ireland, is inside, on top of the insulation, under the final finish, typically plasterboard.