Warm roof details

[jpinthehouse]

Hi

The details I can find for a warm roof are quite different with regards the roofing felt, what have others used

John

 

[ProDave]

The "felt" has to be a breathable membrane, e.g I used Protek VP400, there are plenty of other choices.

[Ian]

@jpinthehouse

Yes, as @ProDave said, use a breathable membrane. Also, depending on the product that you choose for the final roof finish you might need to ventilate the gap between your membrane and roof tile/slate.

Generally, loose fit slates don't need ventilation underneath but close interlocking tiles do need ventilating.

[jpinthehouse]

Thanks for the replies,I'm not sure whether the felt goes under the counter battens onto the pir insulation or under the battens that holds the slate

Thanks

John

[Temp]

+1 to it being vapour permeable/breathable.

 

Check if the membrane is allowed to be installed in contact with the insulation. Not all manufacturers allow this. If they do then I'd put it under the counter battens in contact with the PIR. 

 

Otherwise put it above the counter battens with a gap below. This gap does NOT need to be ventilated like a cold roof construction. The membrane should be allowed to drape between the counter battens so it's not in contact with the underside of the tile battens. This is done to allow water blown under the tiles to drain down the membrane. If there is no drape water can pool above the horizontal tile battens causing them to rot.  

 

Vapour barrier on the warm/inside of the insulation.

 

Fit as much insulation as you can. It will help keep the rooms in the roof cooler in summer. 

Edited July 3, 2018 by Temp