What kind of wood decking is used for roofs?

Panels: plywood and OSB

Most homes built in recent decades have 4 by 8 sheets of 7/16 inch OSB or 1/2 inch plywood over rafters or trusses. They go on quickly, brace the frame well and give shingles a uniform nail base. When a reroof turns up rotted sheets, they are cut out and replaced with matching thickness.

Board decking on older homes

Older houses often have 1x6 or 1x8 boards nailed across the rafters. Tight board decking can be reroofed directly. Boards with wide gaps, splits or loose knots leave spots where shingle nails miss, and shingle makers require a solid deck, so roofers cover it with new panels first. Skip sheathing, boards spaced several inches apart under old wood shake roofs, always needs new panels before shingles.

Tongue and groove plank decking

Thick interlocking planks, often 2x6, span widely spaced beams and stay exposed as the ceiling in cabins, timber frames and vaulted rooms, a common look in North Georgia mountain homes. With no attic, rigid foam insulation goes on top of the planks, often under a vented nail base panel, then underlayment and roofing. Nails must be sized so they do not poke through the finished ceiling.

Choosing for a new roof

For replacement work on a typical home, plywood or OSB of the right thickness is the answer. For a plank ceiling, plan the insulation and nail base with the roofer and your local building department, since energy code applies. See OSB vs plywood roof decking and roof anatomy explained.