Suspended timber floor oversite

[adwt2004]

Hi,

Just wondered whether it's a definite requirement to lay a concrete floor before using suspended timbers in an extension?

I'm sure I've read here that you can put a permeable membrane down with gravel over it which then allows any moisture to drain?

Is that still possible or do I have it wrong?

 

[John D v2.0]

Shouldn't be permeable, you need dpm. The concrete or hardcore it just to weigh it down so it doesn't float away if water comes up under it

 

[adwt2004]

Ok, thanks, I'll use dpm then and weigh it down with hardcore or similar