ᐅ How to Properly Finish an Attic in a Massa Haus GmbH Home in Simmern?

Hello, I live in a Massa prefabricated house built in 1999. I plan to cover the attic to create proper storage space. Currently, there is Rockwool insulation between the rafters, and nothing else—so in the sloped areas and the intermediate ceiling to the upper floor. At the moment, loose OSB boards are lying around so that you can move around a bit.

Now I want to install a vapor barrier foil over the insulation on the sloped areas, followed by OSB boards, also on the floor.

Is this the correct approach, or is there a risk of mold or similar issues? Furthermore, the attic contains a chimney and a chimney sweep hatch made of PVC glass, which is not insulated.

I hope someone can provide more detailed advice, possibly also on which type of foil is needed.

Best regards,
ronnystritzke

Be sure to consult a professional for advice.

You have a cold roof, and there is definitely a reason for that. Under no circumstances should you install the OSB boards tightly against each other. Otherwise, the insulation wool will start to mold.
If you want to lay a floor, use tongue and groove boards. These are breathable. Even then, do not install them right up to the edge—there needs to be airflow underneath.

Leave space at the top and bottom, and preferably space with battens behind it... who or which specialist is responsible for that? An architect?

Best regards,
Ronny

What thickness should be used for the floor? Isn't 23.5 mm (about 1 inch) a bit too thick, since no furniture will be placed on it?

Regards,
Ronny

not on the top and bottom, but on the edge...

BUT I’m not a professional, I’m just repeating what my site manager told me and what seems logical to me. Every carpenter or drywall installer should be familiar with this; otherwise, you should consult a building surveyor, architect, or site manager...

Tongue-and-groove boarding is breathable, meaning moisture can pass through. OSB cannot do that.
Most hardware stores usually only sell 19mm (3/4 inch) material, which is too thin for me; I will install 22mm (7/8 inch) boards.

I got a quote from Leymann for 23.5 mm (about 0.9 inches) panels; they don’t offer anything else. It costs around 10€ per square meter (approximately $10 per square yard), which is quite expensive. I will use drywall for the sloped areas, with a vapor barrier behind it. At the top, near the ridge, I’ll leave it open so any possible condensation can escape.

Don’t you think 19 mm (about 0.75 inches) would be enough? I was planning to screw counter battens onto the valley beam at intervals of about 30 cm (12 inches) anyway...

Best regards,
Ronny