Make cold attic accessible?

Hello community,

I need your help. I want to make my cold attic floor walkable in order to store a few things like Christmas decorations, old school materials of the children, and similar items.

A suitable floor folding ladder is already available. Otherwise, the ceiling structure looks like this (from the living area upwards):

Plasterboard -> counter battens -> vapor barrier foil -> ceiling beams with insulation in between.

I now want to cover the whole thing with 25mm thick tongue and groove boards. I have also had the tongue and groove boards lying in the attic since September.

The ceiling beams are about 8cm wide and have a distance of about 60cm.

Since I cannot screw the tongue and groove boards directly onto the ceiling beams in order to ensure proper ventilation, I certainly need an underlying structure made of roof battens. What do I need to consider here?

- What thickness of roof battens?
- Is one layer of roof battens enough, or better two layers so the air can circulate better?
- What distance between the roof battens?
- What distance should be maintained at the edges to the gable wall and to the collar beam to ensure air circulation?
- Should I treat the tongue and groove boards for protection? If yes, with what?
- Should I also treat the rest of the wooden structure in the cold attic? If yes, with what?
- What else should I consider?

I look forward to your tips, suggestions, and criticism.

Regards Lars

Of course, you can nail the boards directly onto the beams. Where do you see a problem with that? In prefabricated house construction, they build all the walls like that. Rigips, foil, insulation material, wood again.

My understanding was that tongue-and-groove boards are vapor-permeable compared to OSB boards and thus moisture could pass through the wood.

Hello,

Of course, you can nail the boards directly onto the beams. Where do you see a problem with that? In prefabricated house construction, all walls are built like that. Drywall, foil, insulation, wood again.

My contractor has it included in the construction specifications that the covering of the attic, if at all, must be done with at least 4 cm ventilation space.
Excerpt from the construction specifications:

My understanding was that tongue and groove boards are diffusion-open compared to OSB panels and thus the moisture could pass through the wood.

I had read that as well and therefore preferred the tongue and groove boards.

Regards, Lars

I can only say this from practical experience. From 1998 to 2016 we had a [REH] that we sold because of the new construction. My wife and I did the same ourselves with boards on the floor upstairs to use it as storage space, and there were no problems.

I had already installed 40x60 battens on the shell structure. It is then also easier to walk on later. And then I had already carried the tongue and groove boards up. I would like to screw the tongue and groove boards on now. But I will probably wait until next winter. Recently it was good to be able to look under the insulation again, that is, between the foil and the insulation.