new build attic flooring

Archer Hack

Hi,

I'm flooring attic in new build.

Ceiling joises are 225mm. Theres 200mm rockwool between joists and 200mm rockwool accross the joists.

General advice i read is to avoid squashing insulation - this to me rules out laying OSB directly on joists/insulation.

I was thinking to cross batten with 2x3 which would bring the floor up additional 75mm to 300mm. Then lay the OSB/loft board on top of the 2x3. So i would be squashing insulation but will still have at least 300mm there. I might go 2x4 to reduce squashing- mainly just for cost and minimizing reduction in height in loft im thinking 2x3's.

Would you think it would be a noticeable difference with the insulation squashed a bit? Any reason to not do the above or consider alternative?

standardg60

Probably be disagreed with but I don't see the issue with squashing all the insulation between the joists, considering you're adding another insulating layer with the osb.

Lumen

Most analysis of squashed insulation compare a fixed insulation quantity at different levels of squash.

What you're comparing is 200mm of unsquashed insulation to 300mm of squashed insulation.

A greater insulated depth is what's important.

Do it.