My project is to replace 18'x10' flat roof on my concrete garage. So far I installed 16" oc framing and 3/4" plywood over it. Now I am planning to install some fiberglass based underlayment (#30, presumably) and 2-ply self adhering modified bitumen (like SBS Liberty from Home Depot).
Plywood sits about 3" below the top edge of concrete walls (there is a drainage hole at the low point).
So I am figuring how to properly attach underlayment, MB roofing and flashing to the whole structure. I assume that underlayment will have to be nailed or stapled to the plywood. But what size nails do I choose? If I take anything longer than 3/4" it will protrude from beneath the sheathing. Is it ok? How do I properly space it? It surely will not be nice to have this roof covered in spikes from inside.
Do I need to fasten base sheet in addition to it self-adhering to underlayment? What is the best way to attach it to concrete walls? The only way I see is to use some kind of concrete screws. Do I need flashing along all sides of the roof?
I could not find any consistent information on internet so far, so some expert advice would be highly appreciated.