possible to use pir as a floating subfloor, no screed/t&g?

[r6deano]

Evening all,

Trying to find the best way to get the best insulation on a floor for a utility room. currently have 45mm to play with from concrete slab to finished floor.

ideas are either

bed tile backer insulation boards eg, 30-50mm, tile direct, use adaptor profile at threshold

joist out with 2x2, infill with pir, chipboard over

or, prep slab with 2mm levelling screed, lay 40-50mm celotex direct (plus dpm under), and lay floating floor on top.....conscious it may move, just wondered if anyone has successfully done this before in a low traffic small area. I'm guessing as per kingspan fitting instructions, I should prob float an 18mm t&g chipboard over the top for rigidity.

Any other suggestions to get the max insulation with such a shallow depth to work with very much appreciated. Flexi on types of finished floors. Was suggested vacuum panels but looks too niche to get hold of such a small quantity (7m2)

TIA
dean

 

[jeds]

If concrete is fairly flat, lay 25mm PIR foam with 22mm chipboard over. Glue board joints thoroughly. No battens or fixing needed. Leave a 7-8mm gap around perimeter. You could use 18mm chipboard to gain more insulation but the lighter board takes longer to fully settle. Slight variation in flatness might allow some slight movement initially but this normally disappears within a month or two.

 

[Swwils]

Try encon.co.uk to source the appropriate insulation. You should be guided by the proper value from the calcs required for your solution, otherwise you may have issues later.

 

[KenGMac]

As "jeds" above, my son lives in a Tenement block in Glasgow's west end. this property was originally refurbished by a local H/Assn.

All floors are exactly as above, Hall, lounge, even the Bathroom. All PIR foam, it has been that way for over 20 years, all is well with replaced glued laminated floors, and a tiled bathroom floor all floating on PIR.

Ken

 

[endecotp]

If concrete is fairly flat, lay 25mm PIR foam with 22mm chipboard over.

If you use T&G OSB, you can go down to 18mm and get a tad more insulation!