BBA Certified Vapour Permeable Underlay - Do I need to ventilate roof?

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apple1

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Folks (Syd, I imagine you'll be numbered among those who respond to this one!),

I have used a vapour permeable membrane (Vapr Free) in lieu of regular roofing felt under my slates. Does this mean I do not now have to ventilate the roof (i.e. not worry about obstructing ventilated pathways at the eaves) or is there still a requirement to ventilate the roof space. For info, I am using the roof space for habitable rooms. Thanks in advance, apple1
 
Well, thats one for your certifier....
theoretically the construction doesnt need an air vent, however Irish Building Regs require it, so the certifer, to be on the safe side, should insist on one....

this can be done with your makeup by counterbattening over the existing roafters / trusses.... and creating the 50mm cavity there.

look at fig 1 b here..... and dont worrk about the sarking board...
[broken link removed]
 
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