"Glueing" insulated plasterboard to the wall

[JP_]

OK, I was going to get a plasterer to do the last bit of the room (had a quote for about £250) but maybe I will DIY it ....

The wall is old, plastered. Some crumbling, so I've been scraping that with a utility bar to get all the loose stuff off.

So, could I just get some insulated plasterboard and glue it to the wall with adhesive, then paint straight onto it? I know it wont be a great job, but by time I put some pictures up, put the TV there, and a sofa, there won't be much left to see.

Also, the wall is 250cm high, board 240. Is it best to leave a 10cm gap bottom and cover with skirting, or leave 5cm gap top and bottom and using skirting and coving?

Admittedly, I've not looked into how I actually get it to stick yet ....

 

[Doggit]

You can dot and dab insulated plasterboard, but I've glued 25mm foil faced cellotex to the wall, and then glued the plasterboard to that.

Not sure of the size of the wall, but you could put a board along the bottom of the wall, and then cut a second board 130cm high, and keep patching the wall up and down. Alternatively set the plasterboard up toward the ceiling, and use hardwall in the gap at the bottom.

You'll need to clean all of the crumbling plaster off the wall, and it would be sensible to then apply a brick stabiliser to stop any further crumbling.

 

[JP_]

The wall is about 280cm wide. I like the idea of glueing insulation the board on top...

 

[Doggit]

But if you've got problems with the wall, you can't guarantee that the adhesive will grip in all places; hence dot and dab insulated plasterboard is better. You can only do that with the non foiled board, so I suppose you could rip the foil off of one side, dot and dab it with plasterboard adhesive, and then glue it. I only had a 4ft wall to do in the basement, and that took 1 tube of gripfil, so it's not a cheap method.

 

[oldbutnotdead]

If the plaster sounds hollow when you tap it then get rid of it- you need a sound surface to dot and dab to. If you do end up going back to brick, bruah the loose cack off (stiff brush) and PVA the wall before you start fixing.
If you use gripfill to glue the plasterboard to the insulation, use the solvent-free stuff. If you're not going to plaster the wall then use tapered edge plasterboard (so you can fill the joins properly). With your 2500 headroom I'd stick 2400 up to the ceiling and skirting board to cover the gap (150 or 170mm board will look right for that height wall). Or get 8' x 4' plasterboard (1220 x 2440)- even less of a gap to cover!

 

[opps]

Why PVA? Wouldn't SBR be better? I can see that there might be times when you want the PVA to reactivate and become glue-like but if you want to reduce suction, wouldn't SBR, which does not soften when wet, be more apt?

Sorry, I am not criticising your advice but if I were going to use a waterbased adhesive, I would feel more confident if the substrate was not prone to weakening when wet.

 

[oldbutnotdead]

Think the pva is more about sealing an otherwise dusty surface so the goo will stick (you can sweep that wall all you like, its always going to be dusty after you've knocked 100-year old plaster off it). As for pva reactivating when wet- does it? Never noticed it myself (unless you submerge the join for a while)

 

[Doggit]

Exactly, it's got to get pretty wet before it reactivates, but that's not to say that it can't, and we're not on site to make the experienced judgement call. But PVA isn't about sealing a dusty surface, as it quite often will just roll off the dust, it's more about sealing a wall prior to plastering it, so the plaster doesn't get all the mouisture sucked out of it. Horses for courses.

 

[catlad]

I have used expanding foam a lot to glue plaster board/celotex to walls.
You will need clamps until it sets and you will need to lightly spray the wall with water to aid the spreading of the foam.

 

[Doggit]

You should have used adhesive foam instead, as it won't expand, goes off quicker, and is much easier to handle; but well done for having achieved it.

 

[catlad]

I have used both, not much difference really once
you have a bit of experience! Ie. light trigger finger and clamps at the ready I often use a length of 3x2" from one side of the room to the other as a make shift clamp and then jammed it until the foam has cured.

 

[Doggit]

I've used that trick as well; it's a good one, but the adhesive foam doesn't need clamps. You can spray the adhesive foam on, press the two pieces together, take them apart to break the foaming, and then push them back together again, and it just grips; there's no need for clamps when you do it like that.

 

[catlad]

The stuff I used which was specifically for bonding boards
was pink but I can't remember the name.
What is the stuff called that you have used?
is it the pink stuff.

 

[Doggit]

Sounds as though your memory is as bad as mine Catlad. Yup, it was pink, and I think it was called Soudal. But I saw some green adhesive at Ecobuild last year, and it made the Soudal look useless. The guy sprayed it on the board, and it foamed slightly, then shrank back, and when he put the other piece on, it gripped immediately - just wish I could remember what it was called.