OSB or tongue and groove boards for flooring in an expandable attic?

[*]We are building a bungalow with an expandable attic with a 38-degree pitch.
[*]The intermediate ceiling has already received a vapor barrier and insulation.
[*]The roof beams are approximately 24 cm and have a spacing of 50 cm for the insulation.
[*]The insulation with mineral wool is about 16 cm thick.

The roof was actually supposed to remain cold at first. However, we are also considering insulation next summer. We have read about mold with OSB boards and cold roofs, as these are diffusion-tight in contrast to tongue-and-groove boards.

[*]Are 22 or 25 mm OSB boards or 24 mm tongue-and-groove boards better suited for the raw subfloor?
[*]Is a counter-battening useful to allow ventilation between the beams, or should the OSB boards be laid directly on the beams?
[*]Should it be screwed down or installed floating?

Tongue and groove. Make sure to leave some air for insulation. Nail it. Zero nada mold. By the way, 38 degrees is quite witch-house-like. Go down to 30-33. karsten

Tongue and groove boards. Leave some air for insulation. Nail.

Is tongue and groove also the right choice if we insulate the roof and install underfloor heating and laminate flooring?

I don't think so. Something would have to be done with the dry screed, but I am not sure.

Our carpenter had the same concerns. He also thought that a wooden beam ceiling and underfloor heating are critical because wood expands with heat. However, our heating engineer said upon our inquiry that this is not a problem. Nordlys has already given the right keyword: [Trockenestrich].

Tongue and groove boards.

What thickness was installed?