Install flooring in the attic directly on insulation?

Hello everyone

I have a pitched cold roof with a concrete ceiling. A vapor barrier foil is to be laid over the entire surface on the ceiling and then 20cm of styrofoam insulation. What do I put on the styrofoam, i.e. the "floor"?

Tongue and groove boards would be good because they are vapor permeable --> but for that I need a substructure
I can lay OSB boards over the entire surface --> possible problems with condensate
Cement screed --> expensive?

What other alternatives do I have? The whole thing should be inexpensive and not built up too high.

THANKS in advance for your help.

Xps + dry screed

So I don't think you will have problems with condensation. At least not with a concrete ceiling and vapor barrier.

Is ESB a "particle board" or where can I get it from?


I have read online about problems more often. When do you have problems with condensation here?

I would generally advise against using OSB as the last layer on the cold side for wooden ceilings, as the [Folien] are also often poorly installed. However, you have concrete and plan to put a [Folie] on top. I don't know what could be even less vapor permeable.

Do you want to use everything as storage space?

Yes, I want to use it as storage space. Which OSB board thickness do I need, 18mm or 22mm?