Insulated plasterboard or insulation sheet and plasterboard

[purplemonkey]

so I'm about to order up my finish layers and the thermal calculator shows to use insulated plasterboard. but knowing how annoying insulation and plasterboard is to cut. having them glued together just sounds like a right nightmare.

Are the values the same for buying them separately (25mm celotex, and 12.5mm plasterboard) and fixing them independently?

 

[noseall]

It is easier (and more economical) to do them as separates.

 

[purplemonkey]

Yes I think I came to the same thoughts.

any advice on how best to fix them independently.

 

[catlad]

It will take you twice as long buying them individually.

 

[JP_]

yep, separate. Easier to cut, to handle, and cheaper. Plus, does insulated plasterboard have a vapour barrier? Kingspan has one each side, very important to prevent moisture getting through and condensing on the cold side.

 

[KenGMac]

purplemonkey, good evening.

On the work I see they are generally separate

Can i suggest you do some maths? what would Insulated plasterboard cost, as opposed to foil backed board and the 25.mm. insulation?

If you find you are going to save some money on separate ?? you could consider enhancing the spend on the insulation, OK it will take time to get a pay back, indeed if your pockets are deep enough go for as much insulation thickness as poss, that way you will be future proof as far as Insulation thickness is concerned?

The primary reason that I see for individual application is space saving, fit the insulation between the uprights and fit the plasterboard direct on to the upright.

Ken

 

[noseall]

The benefit of fitting separately means that you can stagger the joints of each layer and the insulation board edges need not necessarily land on battens joist or noggs. You also have the opportunity to foil tape the inso' layer prior to boarding.

All in all a far superior more robust way of doing the job. I would NEVER opt for bonded sheets where individual layers is an option. It's only when dabbing we use the Styrofoam bonded type boards. These also require supplementary mechanical fixings so are a faff in any case.

 

[^woody^]

I had a shock just a couple of weeks ago when seeing the price of insulated plasterboard now. What a joke.

Celotex and battens it is!

 

[JP_]

Yep. I ordered some insulated plasterboard last year - about £30 for 20mm of poor quality insulation on plasterboard, instead of about £40 for 50mm kingspan and insulation board.
I sent it back.

 

[noseall]

You will often find the insulation bonded stuff is curved due to the way the laminated layers are bonded under stress. You sometimes struggle to get this stuff to dab straight. Not good at all.

 

[purplemonkey]

yes I have noticed the separates are cheaper, any advice on how to mount the insulation before screwing through the plasterboard?

 

[garyo]

You will often find the insulation bonded stuff is curved due to the way the laminated layers are bonded under stress. You sometimes struggle to get this stuff to dab straight. Not good at all.

For me the biggest headache with this is the precision you need to be able to blindly hit the edge of the rafter without being so close to the edge of the PB that it cracks, or too close to the edge of the rafter that you miss it.

When you're working on a join between two sheets of plasterboard that are mounted over a 50mm PIR layer, are you screwing both sheets in to a ~45mm wide rafter or do you add a batten to the rafter to give yourself a larger target?

 

[purplemonkey]

ah yes thats a good point. I could always use OSB attached to battens first I guess.

 

[JP_]

Everbuild Pinkgrip foam all the way!

 

[purplemonkey]

Hadn't thought of using something like that. so this could be used on both insulation and then plasterboard. does it work over head too?