Fixing insulated plasterboard - general advice

[endecotp]

I think I need to return that I get something completely different, such as foil covered PIR plus plasterboard.

If that's significantly cheaper than the laminated board, and it often is, then yes. Check what seconds&co have.

But then I still have the issue of fixing it to the wall - I guess I can glue just to get it in place, and then mechanically fix when everything is where I want it to be?

Yes, I'd probably glue the insulation to the wall and then glue the plasterboard to the insulation, and put a few mechanical fixings through everything to make it fire-secure.

I'm honestly not sure about glue on foil-backed boards. The only similar thing I've done was celotex pl4000 onto brick using sticky-foam. The back of pl4000 is not "foil colour"; it's cream IIRC, but I think it actually is aluminium (and hence moisture-proof) but with a layer of cream paint or similar. Anyway it sticks fine with sticky-foam, and the celotex website says suitable for dot&dab. I'm not sure about the boards that acually look like aluminium foil.

 

[JP_]

I assume mechanical fixing is needed in case of moisture getting to the adhesive - chap at Siniat said that any moisture on the wall will affect adhesive and it might fall off. They suggested some metal fixing battens to keep everything away from the wall, but these are their own products and I've not seen anybody else mention them!

Still confused. There seems not to be a definitive answer... I just want to be told what to do!

 

[endecotp]

I assume mechanical fixing is needed in case of moisture getting to the adhesive

No, they are for fire safety as explained previously. (They also help keep it in place while the adhesive cures, which simplifies things a bit.)

chap at Siniat said that any moisture on the wall will affect adhesive and it might fall off.

That sounds a bit dubious to me, but I'm no expert.

... I just want to be told what to do!

Celotex & Kingspan both have lots of PDFs you can download. For example: https://www.celotex.co.uk/download/19c803f3-193d-461b-b6b7-8fb070002bbe

 

[endecotp]

Note that the celotex doc describes using dot&dab adhesive, not sticky foam. Here's a stick foam document: https://www.everbuild.co.uk/wp-content/uploads/2017/08/DryFix User Leaf rev.2.pdf

I think reading the two together should tell you exactly whato do!

 

[JP_]

But I have read many times today that you cannot use adhesive on foil backed insulation.
Maybe I'll just in a builder!

 

[Doggit]

It depends on the adhesive. You can't use plasterboard adhesive to dot and dab it, but you could use Gripfill, or adhesive foam (quicker and great fun); and then you can use the adhesive foam to fix the plasterboard to the cellotex, then put in the fixings. Use a long piece of 3x2 to tap the board into place, and flatten it across it's length and height.

Just had a look at the dryfix stuff, and it look interesting, but not sure why you can't use an ordinary foam gun, as long as you clean it out afterwards.

 

[motorbiking]

Moisture is caused by warm air touching a cold surface. i.e. a poorly insulated wall. If you install a decent amount of PIR and I'd suggest 40-60mm as its not that much more than 20-25mm and you do it well, you won't get any moisture behind the insulation as the warm air will be insulated from the cold surface.

Its worth doing well or just buy a dehumidifier until funds permit.

 

[JP_]

Now that sounds like a plan I can follow.

 

[JP_]

So, I will probably see if I can get this:
https://www.mkmbs.co.uk/prodb001449-kingspan-thermapitch-tp10-tf70-tw55-2400mm-x-1200mm-x-50mm/
stick on with https://www.amazon.co.uk/gp/product/B00NVKMCMU/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
then stick on some plasterboard.
Then screw the whole thing into the wall, with these: https://www.screwfix.com/p/fischer-...l+Content&utm_content=TextLink&utm_term=58258

 

[Doggit]

You'll need the adhesive gun as well, and some foam cleaner wouldn't go amiss.

 

[endecotp]

Yes, 50mm of PIR will be more than 4 times as insulating as 20mm of polystyrene.

Do you have a foam gun? If not, Toolstation sell a Soudal product that doesn't need one; the reviews aren't great but you might consider it; videos suggest the mechanism is a lot better than normal foam cans. Also toolstation currently seem to have one of the cheapest "not obviously junk" foam guns for £12.50.

 

[JP_]

I do have one, one I bought for the expanding foam I was going to use to seal the underfloor insulation boards - in the end I cut them the right size and used insulation tape instead. It's a Siroflex contractors foam gun. Not used it yet, but it looks very nice. Hopefully that will do the job. Never used one before though!

 

[Ian H]

I dot and dabbed a load of foil back plasterboards once, they were spec'd on the drawing. They lasted a couple of days

I saw a guy foam PIR onto a wall and that worked.

 

[JP_]

Cross your fingers. 2 minutes to go!

 

[endecotp]

I'm still holding my breath!

(How much did you get on the bedclothes?)