New Flat Roof



Hi I'm looking to spec a flat roof with insulation between the new joists. I've come up with the following from top to bottom:

EPDM sheet
19mm WBP ply
Firrings (75mm max down to 25mm min)
150x50mm strength class C24 joists @ 600mm c/s
100mm Kingspan K7 insulation between joists with 50mm air gap over
Vapour control layer
32.5mm K18 insulated plasterboard

Can anyone advise if seems ok or if there is a better way to do it? I cant insulate over the new joists for lack-of-height reasons.
Sponsored Links
Taking into account that I don't know your span I cant comment on the joist size but the rest looks ok, you will need to vent the 2" void.
If using EPDM membrane i would consider using a tongue and groove deck - OSB3 for example, as it provides a perfectly flat substrate for the membrane to adhere to. Being only 1.14mm thick it will show up all the lips of the boards if they arent super flush.

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links