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Covering celotex insulation boards.

Hi. Do I need to cover the top of celotex insulation boards with plywood, prior to gluing down a E.P.D.M membrane, or can I stick it directly to the celotex boards/slabs?. If you do recommend plywood, does this have to be bonded to the celotex?.As I wish to cover 2 flat dormer roofs and a part garage roof with the membrane, what thickness of insulation boards would you recommend?. I intend to carry out this project not only to give waterproof roofs, but also to keep a lot more heat in the rooms.

3 Answers from MyBuilder Roofers

Best Answer

recommended is 140mm you can use sterling board 18mm secured to your joists , them glue the E.P.D.M. TO THE BOARDS.

good luck alex


Answered 25th Jun 2017

You can also purchase the boards that have the ply and insulation already glued together


Answered 27th Jun 2017

second answer is correct, it used to be called Purl deck but as the norm its called a warm deck. Insulation side down on the joists, no need for ply or similar unless the Bldg. inspector insists on it, ply side up 6mm gaps use correct fixings, loose tape the ply joints and away you go


Answered 30th Jun 2017

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