One concerning thing I have noticed with breathable membranes (tyvek etc) is that they don't have the self-sealing qualities of bitumen felt around nails.
It appears that there will always be a slight gap around any nail or staple which penetrates the membrane, and if the membrane flexes a little, then any such gap gets a little bigger.
So is this a big issue, and could it lead to water penetration under the right conditions?
dg
The sarking goes under the battens so apart from the nails fixing the battens to the rafters there shouldn't be any penetration of the sarking.
I can't really see it as an issue the sarking is only a dirt/draught and secondary water barrier, the slates/tiles by themselves shouldn't be letting any significant amount of wet in.
No - you would use a large headed nail (clout) to fix this and that makes the 'seal' and I've seen literally miles of the stuff laid.
As a matter of interest, I have a broken tile at the moment and the bitumen underfelt (sarking) is holding the rain back admiraly - until it comes to a nail and it's leaking through there onto and running down the roof truss into a bucket.
Perishing rain won't let up enough to let the roofer get up there to whip a crest off, replace the tile and refix the crest - that's life innit? :-)
Brian G
Doh!
I must be a little slow tonight Dave (nah. it's the double Jack Daniel's that I'm scoffing) - what the hell was I thinking about when I said about fixing the stuff with clout nails on a roof - you don't use the damn things in that situation, it must all that crawling in the attic to find the source of a rood leak :-(
Brian G
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