ᐅ Rooms cold on the floor – is insulating the basement ceiling a good idea?

A few follow-up questions about this:

- If you use 2 x 50mm (2 x 2 inches) instead of 1 x 100mm (4 inches), logically you need twice the amount of adhesive (and double the work). This is all “just” for the advantage of being able to stagger the joints – is it really worth it, or is this common practice?

- Does the second layer actually bond properly with standard basement ceiling acrylic adhesive when you are gluing two layers of aluminum foil facing together?

Nanopixel schrieb:

If you use 2x50mm (2x2 inches) instead of 1x100mm (4 inches), you logically need twice the amount of adhesive (and twice the work effort). All of this just for the advantage that you can offset the joints—is it really worth it, or is this common practice?

Normally, this is not done. For example, if a pipe runs along the ceiling, you can simply make a notch in the thicker board. 50mm (2 inches) might hold without support, but 100mm (4 inches) will fall off the ceiling without bracing again.

Nanopixel schrieb:

- Does the second layer stick properly at all with regular basement ceiling acrylic adhesive when you are gluing two aluminum foil facings together?

Acrylic adhesive? Use PU foam adhesive, for example, from Soudal. It sticks like crazy. You could even glue drywall directly onto the insulation and make the ceiling look "nice."

Making the ceiling look nice is actually not necessary.
Thanks for the tip about the PU foam adhesive.
I’m interpreting your "Usually not done" as meaning that two layers of 50mm (2 inches) each are not typically used? And there was no mention of supporting – the thick panels don’t stay directly on top of the adhesive?

Nanopixel schrieb:

I understand your "Usually not done." as meaning that two layers of 50mm (2 inches) are generally not used?

Exactly. There is also 100mm (4 inches) insulation with tongue and groove joints.

Nanopixel schrieb:

The thick boards don’t stay directly on the adhesive on top?

No. Supporting can also mean that depending on the board size, you simply hold the board in place by hand for 3-5 minutes. Or you could quickly make a T-shaped support out of battens and clamp it underneath. I bought some cheap extendable supports for about ten each. For a 120mm (5 inches) board measuring 120x240cm (47x94 inches), four supports are enough; for 120x120cm (47x47 inches), two supports work. It only takes a few minutes each time. While the supports are in place, you can already apply adhesive to the next board – you have to let the adhesive set for a few minutes so it can develop its bonding effect.

How many square meters does a 500ml (17 fl oz) can of PU foam usually cover?

Nanopixel schrieb:

How many square meters does a 500ml PU foam can usually cover?

I use Soudal Soudabond Easy 750 ml for about 10-12 square meters (107-129 square feet). It costs around €12 per can. Really strong stuff 😉