I want to install a metal roof. Can I install over old shingles? Do I need 1x4 Batten boards on 24" centers?

Question

Do I need a vapor barrier?

Answer 1

not over shingles.....u need 15 lbs felt....if instlling standing seam then u dont strip the roof with 1x4....if using the od standard silver metal roof, then we do strip them and then install metal..

lic. gen. contractor

Answer 2

Recent research says that no ventilation is the most damaging thing in metal roofs.  I stripped off my old roof,  redecked in plywood, then added 1x6 nailers on 12" centers.  This allowed me to add ridge vents and allow the air to enter below the metal and vent through the roof.  Not the cheapest, but the longest lasting way.  1x4's would be okay, but again, on 8" centers.  You want to have plenty of wood to s***w into.