Fixing PB to ceiling through insulation

[EvilDonut]

I will shortly be insulating a new pitched roof (single storey kitchen extension) using between-and-under PIR insulation - 100mm Celotex between rafters, 50mm under.

What is the best method of fixing the plasterboard to this afterwards? And how about the fixing of the 50mm Celotex - whats the best way there?

In the past I've used some plastic insulation hammer-in fixings (they had a big circular head), and then some really long plasterboard screws. The long screws were a cold bridge, thus defeating the purpose of the plastic fixings, and the plastic fixings kind of got in the way of the PB - they protruded from the insulation by about 3-5mm. This method was a pain.

 

[Notch7]

I will shortly be insulating a new pitched roof (single storey kitchen extension) using between-and-under PIR insulation - 100mm Celotex between rafters, 50mm under.

What is the best method of fixing the plasterboard to this afterwards? And how about the fixing of the 50mm Celotex - whats the best way there?

In the past I've used some plastic insulation hammer-in fixings (they had a big circular head), and then some really long plasterboard screws. The long screws were a cold bridge, thus defeating the purpose of the plastic fixings, and the plastic fixings kind of got in the way of the PB - they protruded from the insulation by about 3-5mm. This method was a pain.

Its one of the great, or rather not so great issues with fitting insulation.

I suppose sales of long screws mustve shot up! I buy lots of 180mm screws for warm roof construction

 

[EvilDonut]

Ha, ok. Thought that was the only way, was hoping for something better though. Is there a trick you use to actually hit the rafters when screwing those 180mm beasts in? The joists are only 47mm wide and if you're doing an 8'x4' sheet of PB on top of an 8'x4' PIR board, its hard to pinpoint exactly where to screw.

 

[23vc]

100mm drywall screws for the plasterboard, I asked the same question a few weeks back. They take some driving in but they do the trick
I just put a few clout nails to hold the 50mm insulation up, then the boards secure it, no idea if that’s ok or not, didn’t really think about it

 

[Ian H]

I marked the location of the rafters onto the wall, fixed the insulation with 75mm screws and a few metal washers then drew a line across from my marks on the wall onto the insulation.

When I fixed the first plasterboard I copied the marks from the ceiling to the board.

I only missed a couple of times.

 

[catlad]

I started off buying separate plasterboard and insulation to save a few quid but you soon realise that its a waste of time
ie. time is money! and you aren't saving.