Skip to main content

Ready to hire?

Post your job in minutes, browse real reviews and choose who to speak to.Post a job

Need some tips or advice?

Ask a question
Insulation

insulating a flat roof - how much gap should i leave in between insulation and top of the roof?

Anonymous user 03/03/2024 - 3.08 PM

how much gap should i leave in between the insulation and the top of the roof , i'm thinking of getting some kingspan to insulate the flat roof as im having ceiling replastered and this is an ideal time to do it as there is cock all there at the moment but i dont want to end up with a condensation prob by putting too much in and not leaving good gap also do i need to leave a gap in between the plasterboard and the insulation or can it be tight up to it, i know i have to wedge the kingspan in between the beams, total space I have between roof and plasterboard is 4 inch cheers dave --- additional thanks for the info have got the kingspan now but do i need to leave a gap between the foil backed palsterboard and the kingspan or can they butt up to each other leaving just the gap between the roof and the kingspan

Are you a tradesperson and able to answer this question?

Log in

3 Answers

A&J Surveyors Ltd

Rating: 5 out of 5
Newent
If you have 150mm joists then put in 100mm quilt, with a 50mm air gap. Ensure your plasterboard is foil backed to provide a vapour barrier. If or when you renew the roof covering then you should ideally convert to a warm roof to comply with building regulations. This in essence means sandwiching 105mm of TR26 Kingspan between two layers of decking. Best roof covering - fibreglass Second best - EPDM WORST - felt Regards Andrew @ Fibretechs - Glos The advice below is WRONG and would not conform to Approved Document L!
Answered27 July 2014
3

Bruce Willoughby

Rating: 5 out of 5
Chesterfield
use insulated plasterboard (plasterboard with 50mm kingspan on the back)then get a plasterer to come skim it job done
Answered22 July 2014
2