ᐅ Underlayment: White beads – what are they?

Hello everyone,

We are new to the forum and have a question right away:

During the inspection of the roof structure in an older building we are interested in, we noticed a white loose filling material beneath the floorboards. Although it looks like loose polystyrene beads, it is mineral-based and can be crumbled between the fingers.

The roof is said to have been installed in the 1990s. Since the floorboards were also done at that time, it is very likely that the filling was applied then as well.

What kind of material could this be? We need this information to find out whether there is already sufficient thermal insulation on the top floor ceiling.

Thank you very much for any advice!

I just looked up perlite on the web, and it seems to fit. Thanks!

I’m just surprised that the civil engineer present (mid to late 40s) was puzzled. Or could she have been unsure about a specific quality?

Perhaps it was simply the lady’s training — with no offense intended — that was of a certain quality.