Unexpected material between wall and floor

[daggermark]

I live in a timber-framed house. The upstairs external walls are sitting on top of the plywood subfloor, which in turn sits on a joist.

I have noticed that there is actually an additional material sandwiched between the wall sole plate and the subfloor. It is an approx 2mm thick rubber or plastic type material. It seems to be stapled to the sole plate and folds over against the timber inside the wall cavity. If it bend it, it partly holds its shape rather than springing back.

This is more a question of curiosity than anything I need to actually address! Anybody know what this might be and what purpose it serves?

 

[sxturbo]

Pics?

 

[daggermark]

I'd love to but its really awkward to photograph. It's only exposed from the inside in one small area and because its flush against the sole plate it doesn't really show up side-on.

 

[Tigercubrider]

Sound deadening to prevent noise transmission?

I have built internal structures in brick buildings, as recording studios. The key is to isolate the structures on something like 1" thick neoprene rubber or sound will be transferred - even a screw can transmit noise

It could be to prevent the timber building acting as a sound board?

 

[daggermark]

Interesting, had not thought of that. I'd be surprised though, the house does groan a bit like most timber structures, and the upstairs floor transmits plenty of sound. It does seem weird tho to have something like this sandwiched into a load-bearing part of the structure.

 

[^woody^]

Either the detail for interfloor cavity tray/ membrane lap, or part of a radon seal to the frame.

 

[daggermark]

This sounds plausible thanks.