Flooring - Concrete and Insulation thickness

da3533 · 2 Dec 2023

Hello

My garage floor already is already concrete. I want to put 100mm PIR Insulation and was told to put 50mm screed on top.
I need to put a bit more, as in 100mm screed. is this ok or will it be too heavy?

Or can i put 150mm pir insulaton and then 50mm screed?

Suggest i put on concrete first then PIR then screed?

Thanks

motorbiking · 2 Dec 2023

Are you converting it to a habitable space? Might it be easier to just build a floating floor?

da3533 · 2 Dec 2023

motorbiking said:
Are you converting it to a habitable space? Might it be easier to just build a floating floor?

I am converting to a room. Can’t get floating floor, no vents. I would rather screed…

motorbiking · 2 Dec 2023

Floating floor, not suspended timber floor...

bottom up:
concrete
DPM
PIR
DPM (optional)
Timber boards

23vc · 2 Dec 2023

Yes to 100mm screed. Although that’s probably considered towards the tricky end of things to DIY nowadays.

da3533 · 2 Dec 2023

23vc said:
Yes to 100mm screed. Although that’s probably considered towards the tricky end of things to DIY nowadays.

Thanks. Why tricky?

23vc · 2 Dec 2023

Because mixing and laying sand and cement screed is fairly hard work to do and get right, if you haven’t done it before. Floating floor much easier.

da3533 · 2 Dec 2023

23vc said:
Because mixing and laying sand and cement screed is fairly hard work to do and get right, if you haven’t done it before. Floating floor much easier.

Oh. No I was going to get someone to pour it on .

noseall · 2 Dec 2023

da3533 said:
Oh. No I was going to get someone to pour it on .

Liquid screed? You'd be better off increasing the insulation thickness.

For sand/cement screed, more thickness can be beneficial regards an unbonded lay.

Ivor Windybottom · 4 Dec 2023

Is there a weight limit for PIR? 100mm or 150mm concrete is often laid on top of it.

Presume there is a limit though, but I don't know what it is.

But as suggested above, more PIR and a sheet of chipboard would be less hassle and better insulated. I have a room like this, I can confirm it's not the bouncy castle I imagined it would be. I put timber of the right thickness under each doorway, in place of the PIR, bolted down into the concrete then screwed the chipboard into it, just to ensure it wasn't bouncy at the edge. I don't know whether this was necessary, the rest of the room is rock solid. 22mm chipboard is much better than the standard 18mm.