How To Fix PIR Below The Rafters

[EViS]

We will be installing celotex/kingspan inbetween our roof rafters, leaving a 50mm air gap.

We will then be installing celotex/kingspan below the rafters and have a question about the installation.

1. What's the best way to fix celotex/kingspan below the rafters? And how would we then fix the plasterboard over this?
2. If we opt for celotex/kingspan which is already adhered to plasterboard, what's the best way to fix this to the rafters?

 

[dann09]

FWIW: it's simple enough to pin sheet materials to rafters, but there are a bunch of other variables to consider. Why not call the Mfr's customer service/tech advice and get best practice for your situation.

 

[EViS]

I gave them a call, their answer was, and I kid you not, "they do not offer advice on fixing methods". What!?

 

[^woody^]

Use screws!

A few in the insulation to hold it, then screw the p/b as normal

 

[EViS]

No need for any washers to stop the insulation from popping through the screw?

Are drywall screws the most cost effective option here? Screwfix doesn't seem to stock these in lengths over 100mm. To be comfortable, I would need around 120mm screws to secure the plasterboard through the insulation and into the rafters.

 

[Zebra579]

I believe that drywall screws are the norm, but I know what you mean, they tend to disappear into the insulation. What I did, was to use small squares of cardboard, just to stop the screws from disappearing into the insulation. Then when it's all up and you are ready to fix the plasterboard, just pull the bits of cardboard away, or leavethem in, it makes no difference, and fix the plasterboard using more drywall screws. This may not be a professional solution, but seems to work!