Flat Roof Insulation

[blake floyds]

Can any one tell me the min amount of insulation for a new flat roof extension my joists are 8" and i am thinking of having a cold roof with an air gap

can not get in touch with my B C O

Thanks

 

[noseall]

full fill celotex no need for any vent's.

 

[festive]

I was going to ask the same, i was going to use heavy duty rockwool and 15mm Soundblock plasterboard on the ceiling as it's an outbuilding in garden and will be playing my music loud in there.
Why no ventilation gap anywhere like you have in conventional roofs?

 

[^woody^]

You will need insulation over or under the joists to prevent a thermal bridge by the joists, so even if a quilt is used, you may also require some board insulation (celotex/kingspan) too

Quilt will normally be 250mm and board will be 120mm, but depending on the design then a further 25mm of board may be required below or above the joists

 

[Deluks]

I was going to ask the same, i was going to use heavy duty rockwool and 15mm Soundblock plasterboard on the ceiling as it's an outbuilding in garden and will be playing my music loud in there.
Why no ventilation gap anywhere like you have in conventional roofs?

Track down some resibar/resilient bar/resilient channel, and fix that to the ceiling before attaching 2 layers of 12.5mm plasterboard.

Make sure you know exactly how to install it, contact the manufacturer or search the gyproc website for details.