Plywood Over Plank Roof

This is particularly important if your old sub floor has lumps and bumps in it.

Plywood over plank roof.

After the 1960s the predominant residential roofing substrate became 1 2 cdx plywood. The plank problem typically sheathing problems are isolated to small areas but old plank sheathing presents more of a challenge. On older homes planks were often spaced for wood or slate roofs with wider exposures than the standard 5 inch tab on asphalt shingles. Plank sheathing usually 1 6 or 1 8 was used as a roof deck before plywood.

In the first half of the 20th century roofs in missouri were built with wood shingles over planks spaced about 1 apart. It was common practice to have a clause in the contract that once the roof was stripped down depending on what was found plank roofs that were not already covered with plywood would then need to be covered in order to do a good job and provide a solid warranty. These 8 to 12 inch wide boards were nailed together tight. Use decking screws to secure squeaking planks through 1 4 ply to joists.

The keyword here is solid it used to be standard to use shiplap 1 boards tongue groove or other boards for the roof deck. Things to take into account when laying ply over plank subfloors. 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. Repair any broken planks.

Personally i like plank spaced decking. Over time shiplap fir wood resin dissipates causing the boards to shrink crack form knot holes and become extremely brittle. Most western washington residential homes during this time were built with shiplap roof decks rather than plywood. As roofing contractors in seattle we are often asked why do we need plywood over our old solid sheathing.

Take time to make sure your existing planks are well secured in place. Plywood is layers of wood plywood is made. Why re sheet over shiplap. Open spaces form between the once tightly fitted shiplap boards.

Today a shiplap roof is usually 60 years old. The issue guertin explains is the gaps between boards. Its really common here too to see 3 8 plywood used on roofs from the 70 s. Or they could place osb or plywood over current planking.

But the spacing should not be more than quarter inch. In that case they could whe replacing shingles fill the larger gaps with firring.