ᐅ Thickness of the installation boards for the attic?

Created on: 16 Oct 2016 10:18
S
SanSabin87
Dear forum members,

We will be receiving a prefabricated house at the end of the year. The floor of the unfinished attic will remain open, meaning the ceiling joist structure will be visible and not yet walkable.
We would like to make the attic floor walkable by installing cross battens and then laying floorboards on top, so that we can store a few items up there.
I hope someone here has experience with this and can advise me on the spacing for the battens and the thickness of the floorboards needed to ensure the floor is safely walkable.

Thank you in advance for all your responses.
P
Peanuts74
18 Oct 2016 08:40
Bieber0815 schrieb:
In my opinion: hardly any moisture will penetrate from the house into the insulation (since the house is sealed), but the insulation, despite the OSB boards on top, is exposed to the atmosphere, and eventually the dew point will be reached somewhere (at night, during weather changes), and once mold appears ...

Why are the boards exposed to the atmosphere?
We also use OSB boards that are 22mm (7/8 inch) thick. On an area of about 1m² (11 sq ft), there are 300kg (660 lbs) of leftover tiles standing on them. According to the construction company, 18 or 19mm (3/4 inch) thickness would also be sufficient; it depends on the spacing between the battens/beams.
We have also left about 5cm (2 inches) of continuous air gap around it, and so far everything is fine...
B
Bieber0815
18 Oct 2016 11:03
Peanuts74 schrieb:
Why are the panels exposed to the atmosphere?

Because the roof is not "sealed."
P
Peanuts74
18 Oct 2016 11:14
Bieber0815 schrieb:
Because the roof is not "sealed".

That is not generally the case; a warm roof, which I would always prefer, should be sealed. Even if you only want to store wood decorations, I would be reluctant to expose them to the temperature fluctuations of an uninsulated roof...
B
Bieber0815
18 Oct 2016 12:33
I assumed the setup would be vapor barrier – insulation – attic space. If the attic is located within the airtight, insulated building envelope, this problem does not occur (though in that case, I would be consistent and properly finish the attic).
C
Caspar2020
18 Oct 2016 13:07
Peanuts74 schrieb:
That’s not generally the case. A warm roof, which I would always prefer, should be airtight. Even if you just want to store wooden decorations, I wouldn’t want to expose them to the temperature fluctuations of an uninsulated roof…

However, the original poster clearly did not refer to a warm roof, nor do they have one:

“We are getting a prefabricated house at the end of the year. The floor of the unfinished attic will still be open. That means the…”

In prefabricated houses, it is almost standard to have a cold roof space.