Subfloor on celotex - choices - grateful for advice

15 Mar 2012
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United Kingdom

In the midst of renovating rooms on the ground floor. It's an old church, with a concrete slab floor over DPM.

I'm planning on insulating the floor with 50mm celotex, and was looking at putting 18 or poss 22.5mm T&G chipboard over the top for the subfloor. 50mm with floating chipboard layer, is about the max I want to lose from room height (and I've got the Celotex).

However, reading online, that might not be optimal if we want to (ideally) lay a reclaimed solid wood floor of some description. I think it would be ok if we went engineered and presumably floated an engineered floor on the floating chipboard layer?

I did think of installing 2x2" battens instead, with 50mm celotex insulation between and laying the reclaimed floor over the battens, but that gives cold bridging and from the calculator means I'd need min 65mm celotex to achieve the right U value.

I've only bought the Celotex at this stage, and would be grateful for any advice as to the subfloor choice before I plump for chipboard? Is is as simple as a) chipboard + engineered floating floor or b) rafters, insulation between, and reclaimed or are there other options I might consider in this situation?

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