ᐅ Insulating the upper floor ceiling. Vapor retarder on the floorboards, is using friction-fit mineral wool acceptable?

Hello,

I bought a small house built in 1957 and now want to insulate the ceiling of the upper floor. I have partially removed the floorboards, and this is what it looks like: below the beams, there are hardboard panels coated with plaster on the room side. The cavity is empty, no slag or anything else inside. However, there are many screw tips visible, probably screwed from below—I don’t know why.

I originally planned to line the cavity with a vapor retarder (not a vapor barrier), then install 160 mm (6.3 inches) of mineral wool insulation pressed in, followed by a 2 cm (0.8 inch) air gap, then a breathable roofing membrane, and finally the boards installed with a ventilation gap of about 5–10 mm (0.2–0.4 inch).

Since the effort to remove all the screws is huge, I need an alternative. My idea was to place the vapor retarder on top of the floorboards, then install the mineral wool on top. At the chimney passage (for the chimney sweep), I would place wooden battens between two layers of mineral wool to create a board walkway to the chimney. Is this feasible?

I am financially completely stretched, so blown-in insulation is not an option. I hope someone has advice for me.

I have exactly the same problem, except in my case it’s nails sticking out. I’m not sure how to proceed either.

Hello, I bent the screws, placed an impact sound insulation in the cavity, and then installed the vapor barrier. It worked ;-)

Fescha63 schrieb:
Hello, I bent the screws over, placed an impact sound insulation in the cavity, and then installed the vapor barrier. It worked ;-)

Well, I just hope for your sake that you never have to unscrew those screws...

Otherwise, that could turn into a real tough job.

If I ever have to do that, it would only be if the formwork of the upper room ceiling needs to be removed :-)

Because of the nails sticking out in the infill panels, could I also place 2-3 cm (1-1¼ inches) thick polystyrene boards there and then cover them with a vapor barrier foil, or would that already cause condensation?