OSB board on paving stones in carport

Please note that interior insulation is very prone to mold. I would suggest laying [Schweiß ahnen]. Then leveling fill and finally walkable insulation boards for the attic. Alternatively, PUR or PIR boards and finally cheap click vinyl.

If the room is not to be heated like the house, but only kept frost-free and warmed when the workshop is used, I would keep the insulation minimal and allow fresh air. Put on a sweater, aim the infrared panel, and that's it.

Yeah, a workshop doesn’t need insulation. I also don’t understand what speaks against just leaving the paving stones as they are.

As previous posters have already pointed out: better not to insulate and rather install an infrared panel if needed.

A hut where one laughs is better than a palace where one cries. (Chinese proverb)

Nice signature

Hello "scotti07". It is actually as the previous speakers have written: OSB is not very suitable. The harmful factor here is not moisture penetrating from the back (because of the "thicker" PE foil as a vapor barrier), but the humidity associated with the lack of heating in the autumn and winter months. I would design the structure similarly, i.e. possibly level the concrete pavers, lay PE foil at least 0.2 mm thick and pull it up at the edge above [OK Fußboden], set grid-like support beams with a maximum spacing of 50 cm and adjust their height. Fill the compartments in between with thermal insulation; however, for a functional insulation layer you already need 10 cm! On top, as a load-distribution layer, moisture-resistant gypsum fiber boards, at least 35 mm thick, ideally laid crosswise in this thickness (for high loads). Regards: KlaRa