Fixing plasterboard to IWI

[Hammertime]

I've got hollow cavity walls, internal leaf is thermalite. I've stuck 50mm PIR to it with PU adhesive, and I will use the same to attach plasterboard to the PIR, but I think I need some mechanical fixings through to the thermalite too.

What would people recommend?

- Twistfix make one but it's metal and they say it can cause thermal bridging.

- There are hammer-in fixings but again, the only thermal break is a thin piece of plastic and the screw is metal

- There are some plastic plugs with fibreglass pins to nail in like the Fischer DIPK, which is probably what I'll use if there's no better option - only problem is the disc heads are about 3mm thick, so skimming over could be an issue.

 

Is there anything more suitable that you know of?

 

Thanks

 

[Russell griffiths]

How are you running services, you could run a service batten on top of the insulation then fix plasterboard to that. 

[Mattg4321]

Why didnt you use plasterboard that comes already attached to the PIR out of interest?

 

I'm not sure there's any approved method of using mechanical fixings into masonry to fix plasterboard.

[Hammertime]

Thank you both. That could be an option, @Russell griffiths - I've generally tried to avoid running services on those walls eg putting sockets on internal walls where possible. My concern would be that I still need to pierce through the insulation to the thermalite in order to fix the battens and the plasterboard would be on top of those screws, so it's whether the margin of benefit would be worth the extra space lost. 

@Mattg4321 I decided to go that route partly for cost (it was much cheaper buying them separately) and partly because I can then foam and tape the PIR so the insulation and its foil facing are both continuous, which I thought would be harder with combined insulated plasterboard. 

There are some plastic plug and pin fixings here on insulationuk that look similar to the Fischer dipk ones, but it specifically says it's not for insulated plasterboard. I wonder why that is? I phoned them and couldn't get a definitive answer. Maybe because the disc is 3mm. If so, could I recess the disc slightly in the plasterboard then scrim over?

[Mattg4321]

6 hours ago, Hammertime said:

Thank you both. That could be an option, @Russell griffiths - I've generally tried to avoid running services on those walls eg putting sockets on internal walls where possible. My concern would be that I still need to pierce through the insulation to the thermalite in order to fix the battens and the plasterboard would be on top of those screws, so it's whether the margin of benefit would be worth the extra space lost. 

@Mattg4321 I decided to go that route partly for cost (it was much cheaper buying them separately) and partly because I can then foam and tape the PIR so the insulation and its foil facing are both continuous, which I thought would be harder with combined insulated plasterboard. 

There are some plastic plug and pin fixings here on insulationuk that look similar to the Fischer dipk ones, but it specifically says it's not for insulated plasterboard. I wonder why that is? I phoned them and couldn't get a definitive answer. Maybe because the disc is 3mm. If so, could I recess the disc slightly in the plasterboard then scrim over?

I understand why you did this, as I also did the same. That insulated board is impossible to detail properly in my opinion. 
 

I fixed it slightly differently to you though. I didn’t stick the PIR. I fixed through 18mm thick battens (then through the PIR) into the blockwork and then screwed plasterboard to the battens.