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

Boards flat. Thickness n.a. Just boards.

Which thickness was installed?

For our wooden beam ceiling ground floor/upper floor, which is to be inhabited, we have a thickness of 28.5 mm – for the wooden beam ceiling upper floor/attic a thickness of 23.0 mm

We will screw tongue and groove boards 3000x146x27 directly onto the beams. I want to lay the boards in a random pattern. For this, it would be necessary to either saw each board individually so that it ends on a beam or let them end between the beams (distance <50cm).

Does anyone have experience whether tongue and groove prevents vibration? Or should I let each board end on a beam and therefore cut them individually?

Why the extra effort? If the [OG] is being converted, you won't see the wild bonding pattern anymore anyway?! I would keep it simple and additionally always let the boards end on a beam. When you convert, there will be a lot of weight on it and I wouldn't really trust the 50 cm overhang.

I would keep it simple and always let the boards end on a beam. When you finish, there is a lot of weight on it, and I wouldn't really trust the 50 cm overhang.

That's exactly what makes it complicated if I have to saw each board to length. Random bonding means I only saw when there's an obstacle.

Rauspund. Pay attention to some air space for insulation. Nail. Zero nada mold. By the way, 38 degrees is pretty witch-house-like. Go down to 30-33. karsten

I am currently, besides many other construction sites :) also planning how to best convert the cold roof into a small storage space. Therefore, I am bringing up this topic again. I quite like the picture with your solution. I would have less height with a (gable roof), but it should be enough for storage. I would now first screw battens onto the roof beams (40x60) and then put tongue and groove boards on top. Probably planed spruce (2000x115x19). To allow the air to circulate underneath, I would also leave space at the edges. Maybe a bit less than in the picture. That should be okay so far. However, I still have 8 rolls of between-rafter insulation (30cm thick) left over from the insulation work on the upper floor ceiling. Does it make sense to insulate the cold roof now and then simply tack foil (vapor barrier) over it so that the insulation wool is not freely accessible? Or would it be best to leave the roof completely cold?