Fitting new slate roof questions?

[Ruggers]

I have a few questions. I'm building an outhouse out of block with 4" x 2" roof spars, It is a lean to roof. The finish is going to be slate 500 x 250mm.

What size batten thickness is recommended 19 x 38mm?

What's a decent breathable felt I need 25m.
And if I'm going to ply the roof is it best to do it on the inside to the underside of the spars or can I lay them on the top to the spars then lay the felt over the ply and battens on top or will it not breath this way?

And finally what size nails and are aluminium clout nails ok?

 

[ners]

If your rafters are no more than 450mm appart then 19mm lath will be fine, personally I would still go for 25mm lath though. We sell a felt called "maxi" which is perfect for what you need (not cheapest but not as expensive as others). You will need 30mm slate nails, alloy or copper is your choice. You don't need to ply the roof.