flat roof

[electrified]

Hello, what i am planning on doing is having 4x2 joists with osb and epdm roof.

i plan to put moisture resistant plasterboard and will put 50mm of insulation tight to the plasterboard, which will leave about a 50mm gap of air.

I now know i need ventilation, to which i will be putting fascia board air vents to allow for this on 3 sides.

I will also be adding some down lights which i will cut a bit out of the insulation and run the cable in the 50mm air gap. Has everything i have said compliant or nearly lol.

I do recollect something about a clear sheet that is resistant to moisture also, if i need this where should i put it.

Many thanks.

 

[CACKATALLTRADES]

Why do you need water resistant plasterboard unless you're planning on the roof leaking? Do you mean vapour check plasterboard?

Not sure it's wise to compromise the insulation by cutting chunks out of it, but equally you need clear space around a downlight for heat to dissipate. I'd have thought you'd want a ceiling with a proper void for this unless you get very low wattage low profile lights.

 

[electrified]

Why do you need water resistant plasterboard unless you're planning on the roof leaking? Do you mean vapour check plasterboard?

Not sure it's wise to compromise the insulation by cutting chunks out of it, but equally you need clear space around a downlight for heat to dissipate. I'd have thought you'd want a ceiling with a proper void for this unless you get very low wattage low profile lights.

yes that what i meant sorry vapour plasterboard, i have downlighters that need a 40mm gap, so that should be ok. I just need to know if my 50mm insulation with 50mm gap, with through ventilation will cause me problems?

Thanks