PIR underfloor

[damessiahuk]

Hi- I'm looking to install PIR between joists on ground floor to insulate.

My plan was to screw battens to side of joists for PIR to sit on but was thinking I could screw batten at horizontal to joist from the underneath for it to sit on. This would require far less batten as could use 4 or 5 across the entire room width, and I can use thicker PIR.

Otherwise it's two battens on every joist.

Anyone done something similar? And what did you use?

(I was also thinking maybe an edging profile instead of battens if I did the each joist route)

Thanks

 

[Mr Chibs]

You could screw roof battens at 90° to joists, these are around 25x50mm.
If the insulation is cut tight, the battens would be a bit reassurance, but probably not necessary.
I put a building paper on top of the joists/insulation stapled onto joists, then wood floorboards.

What flooring are you intending to do?

 

[damessiahuk]

You could screw roof battens at 90° to joists, these are around 25x50mm.
If the insulation is cut tight, the battens would be a bit reassurance, but probably not necessary.
I put a building paper on top of the joists/insulation stapled onto joists, then wood floorboards.

What flooring are you intending to do?

Thanks- reassurance what I'm after as I suspect they will move over time! What you've said is what I was thinking about doing as less battens so that's great, just wanted to check I'd not missed something (recognising space underneath to actually do it may be tricky!)

There's an overlay UFH going on top

 

[damessiahuk]

I was debating just putting the floorboards that are coming up on the underside to support

 

[geraldthehamster]

You don't need battens. Cut the insulation sightly undersize. Insert screws horizontally and sit the insulation on them. Squirt expanding foam down all the sides to seal the foam to the joists. That's what I did