polythene membrane 500 gauge

[paulpa]

Is there a certain type to use over celotex before screeding in underfloor heating, and is it laid up the walls like the dpm sheet?
Celotex quote.
"A polythene membrane on top of Celotex below a screed or concrete oversite performs three tasks: it acts as a VCL; it prevents migration of the screed / concrete which can force the boards apart leaving cold spots in the floor; and (most importantly) it prevents a reaction between the wet screed / concrete and the foil facer of the Celotex which can cause a reaction whereby the Celotex is burnt and gases are given off leaving weak pockets in the screed / concrete."

 

[mointainwalker]

No. It just has to be strong enough not to tear when you lay it and whilst the screed is drying. 500 will be fine.

You need to take it up the walls too. The same height as the cushioning strip/polystyrene against the walls.

 

[paulpa]

any idea where i can get a clear one, having trouble finding any large rolls?
found some at the build centre.