garage roof - plywood or sarking

all help appreciated again.....
i'm putting up the roof trusses on the new garage next weekend and want to batter on to ensure a felted roof (ready for slates) before xmas.
my current question is whether to use plywood or "sarking"?
i understand that plywood is quick and economical - sarking is perhaps a bit more labour intensive - planks instead of sheets??
however, is there any advantages to using sarking - my labour's cheap ;^)
that said; what's the recommended thickness of sarking?
if plywood's the recommendation, what would be the best thickness.
the roof's got a 36 degree pitch and covers a span of 7m. the garage is 10m wide.
also, what's the recommended roofing felt which will hold out for a few months until i get the slates sorted out? do i need battons or should the slates be nailed straight onto the sarking/ply?
thanks paul
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Why are you using ply and what is Sarking? Why not just use a breathable felt, bit more expensive but then you do not need vents in the fascia, slates or ridge. You batten on top of this using the correct sized battens at the correct spacing for the slates you are using This will then keep out the rain and wind (but not cold) for a shortish period until you put the slates on. Felt available from your local quality builders merchant or roofing centre. Probably not from sheds
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Paul wrote:

Builders merchant would be likely to deliver OSB roofing boards, but not sure many people would bother at all, just felt then battens over the rafters: lowest cost option. Boards would provide some 'nail in anywhere' flexibility for the slates. Mind you, if this is a super deluxe heated workshop rather than a plain old garage, then adding insulated boards such as Celotex Double-R or Kingspan Kooltherm K7 would be ideal. http://www.insulation.kingspan.com/newdiv/k7.htm

There's a bungalow near me that has been sporting ScrewFix's 'protect' twin-ply polypropylene roofing felt since the end of summer, it's about 1 per m2 (Item 31795). Apparently a lot easier to handle than bitumen felts . Still seems to be keeping the elements out, I guess they must be struggling to find a slater.
Definitely needs battens in this case, holds the felt down properly for one thing, but you will need to have some slates on hand so they can be spaced and positioned correctly.
--
Toby.

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