Warm Roof Insualtion Information, help and advice on maintaining, installing and repairing a flat roof. Post your questions and view answers here

[highlandbee]

is it possible to use EPS 70 polystyrene insulation in a warm flat roof, with timber deck. If so what thickness would be needed to achieve a U value to satisy building control, or is PIR rigid insulation the only option. Also can edpm be layed on top of this, or wpould anpother ;layer of plywood be needed?

[andy01]

ask the maufacturers if their product can be used in this application, speak to their technical department. they may require a sketch of teh detail to help them answer your questions.

[Aspect Roofing]

Hi I'm new to the site :-)

King span supply a insulated board which comes with a plywood surface so it's ready for rubber or felt to be applied. If your interested I can put you in touch with my suppliers.

Regards Richard

[charlienamatjira]

We have classic cold loft insulation installed in the plain of roof pitch due to warm roof.Since we already had insulation before this so less than 100mm depth of insulating material is used.

[RubberRoofer]

You need FRMG (Mineral faced) PU or PIR insulation board.

Around 120mm of this will give a U value of approx 0.188 - you then need to calculate your existing insulation into that as well.

If you already have 100mm of rockwool in the ceiling void, then 70mm of PU should be fine.

Do NOT use polystyrene - not strong enough to walk on, fire risk etc etc. and glues won't take to it either.