Gap filling when applying a plasterboard to an uneven wall.

[RichD1]

As it says, what gap will a foam adhesive fill behind when fitting plasterboard to an uneven wall. It's an old brick and concrete block wall which varies about 5mm to 100mm.

 

[motorbiking]

5-100mm? Thats quite a gap. Plasterboard adhesive foam will go to 20-25mm.

If you've got 100mm in places I think I'd be tempted to chip lumps off, or fit with some celotex.

 

[RichD1]

Typo!!! Should have been 10mm. From what you've said I shouldn't have any issues. Does the foam compress with a degree of force? Wouldn't like it to push in too easily as I'm boarding to some existing plaster.

 

[motorbiking]

No its solid once dry. You'll go quicker if you put some fixers in as you go to hold it while it cures.

 

[RichD1]

No, I meant when you're putting the board up. I don't want it to compress too easily as I'd like to be able to tap it in with a long straight edge so it will sit level with some old plaster above. Fixers, hadn't thought about that. I assumed it was a grab type adhesive especially as it has to go off a bit before fitting. How long till it does it take to cure enough to hold a 1.5M x 1.2M board in place?

 

[motorbiking]

You have the advantage of being able to inject some extra behind if its over compressed. It takes about 10 mins to hold.

 

[foxhole]

Apply foam , wait 30-60 secs for expansion and press to wall , this kills the expansion and sticks to anything it touches .

 

[RandomGrinch]

I have often used the Soudal low expansion adhesive plasterboard foam.
I find it is a good, easy to use product.
Currently at decent price from B&Q:

Soudal Genius gun Plasterboard adhesive 750ml | DIY at B&Q

Genius Gun Plasterboard Adhesive Foam by Soudal is a fast curing polyurethane adhesive that provides a simple, clean and efficient alternative to traditional mortar based methods. Perfect for bonding plasterboard panels directly to masonry or timber battens. Can also be used to bond decorative...

www.diy.com

The instructions are - after spraying the foam onto the board, leave for 4 minutes, then press the board onto a dampened wall.

 

[RichD1]

Glad you mentioned Soudal as I've just bought some but unfortunately our local B&Q were out of stock. How big should the bead be to ensure a gap fill of 10mm?

 

[RandomGrinch]

Glad you mentioned Soudal as I've just bought some but unfortunately our local B&Q were out of stock. How big should the bead be to ensure a gap fill of 10mm?

Because it's low-expansion and quite easily controlled, you get a good idea of the bead size when you are spraying.
If the bead looks a bit thin when you get around to the other side, just add a bit more.

 

[motorbiking]

you make a line around the edge and zig zag the middle. Its good stuff, if a little expensive now. I normally give it a minute and usually stick a few scews and plugs around the edges.

 

[lc155]

No its solid once dry. You'll go quicker if you put some fixers in as you go to hold it while it cures.

You're saying the foam adds structural integrity to the areas with voids? I've been debating using some kind of powdered tile adhesive that sets hard (but it may shrink when curing or crack/become brittle with time) or foam, but figured foam wouldn't actually offer support against compression if anything was ever fixed to it.

 

[motorbiking]

It sets hard.

 

[lc155]

It sets hard.

So you definitely rate the foam over any kind of hard setting powder then?

 

[motorbiking]

yes. I've used it on several projects.