I am in the process of replacing my wood shake roof with asphalt shingles. The original redwood shake roof was installed in 1980 over 1x6 inch pine skip sheathing. While I liked the look of wood shakes, fire code now prohibits their use in our area. Also seismic considerations now require plywood (or OSB) in place of the skip sheathing regardless of roofing material. We have decided to use asphalt shingles over plywood decking as replacement roofing.

The question I have is how best to re-roof while minimizing labor costs. Removing the old shakes is the first step regardless of how the plywood sheathing is applied. The question is how best to prepare the roof surface to add the new sheathing of plywood. The old shake nail heads will be protruding from the skip sheathing after removing the shakes that needs to be smoothed prior to attaching the plywood. We could 1) remove all the old skip sheathing, shakes and metal flashings at the same time we remove the shakes. Then attaching new plywood directly to the rafters. Or (2) remove the olds shakes and flashings alone. Then pound down and/or remove the shake nails from the skip sheathing. Plywood over the now smoothed skip sheathing, nailing into the rafters. (3) Any other ideas?

Alternative (2) is more labor intensive then (1). Thanks Konstantin