Plywood Over Plank Roof

Or they could place osb or plywood over current planking.

Plywood over plank roof.

Plywood used for roof decking is typically called sheathing and carries a grade stamp indicating its load and span ratings and other performance factors. In the first half of the 20th century roofs in missouri were built with wood shingles over planks spaced about 1 apart. Things to take into account when laying ply over plank subfloors. Install a layer of at least or preferably 5 8 ply over the existing planks.

Today a shiplap roof is usually 60 years old. These 8 to 12 inch wide boards were nailed together tight. Plywood is layers of wood plywood is made. Over time shiplap fir wood resin dissipates causing the boards to shrink crack form knot holes and become extremely brittle.

The keyword here is solid it used to be standard to use shiplap 1 boards tongue groove or other boards for the roof deck. In that case they could whe replacing shingles fill the larger gaps with firring. The issue guertin explains is the gaps between boards. The plank problem typically sheathing problems are isolated to small areas but old plank sheathing presents more of a challenge.

This is particularly important if your old sub floor has lumps and bumps in it. Repair any broken planks. As roofing contractors in seattle we are often asked why do we need plywood over our old solid sheathing. Open spaces form between the once tightly fitted shiplap boards.

But the spacing should not be more than quarter inch. We resheet with 1 2 osb right over top of the old all the time be it 3 8 ply or old t g boards in the case of the old t g boards it makes for a flatter surface plus greatly lessons the chance of nailing into the gap between boards. Why re sheet over shiplap. Most western washington residential homes during this time were built with shiplap roof decks rather than plywood.

Take time to make sure your existing planks are well secured in place. On older homes planks were often spaced for wood or slate roofs with wider exposures than the standard 5 inch tab on asphalt shingles. Use decking screws to secure squeaking planks through 1 4 ply to joists. Use door skins to raise dips to 1 8 use contact cement to secure to existing 1 4 ply secure 17 32 plywood to the planks with 1 5 deck screws avoiding the joists to allow slip install engineered hardwood over the new subfloor w underlayment if needed.

After the 1960s the predominant residential roofing substrate became 1 2 cdx plywood. Personally i like plank spaced decking.