Plywood Over Plank Roof

Take time to make sure your existing planks are well secured in place.

Plywood over plank roof. Install a layer of at least or preferably 5 8 ply over the existing planks. As roofing contractors in seattle we are often asked why do we need plywood over our old solid sheathing. Repair any broken planks. But the spacing should not be more than quarter inch.

Today a shiplap roof is usually 60 years old. On older homes planks were often spaced for wood or slate roofs with wider exposures than the standard 5 inch tab on asphalt shingles. Open spaces form between the once tightly fitted shiplap boards. This is particularly important if your old sub floor has lumps and bumps in it.

Or they could place osb or plywood over current planking. Its really common here too to see 3 8 plywood used on roofs from the 70 s. Plank sheathing usually 1 6 or 1 8 was used as a roof deck before plywood. Things to take into account when laying ply over plank subfloors.

The keyword here is solid it used to be standard to use shiplap 1 boards tongue groove or other boards for the roof deck. Use decking screws to secure squeaking planks through 1 4 ply to joists. In the first half of the 20th century roofs in missouri were built with wood shingles over planks spaced about 1 apart. Plywood is layers of wood plywood is made.

The plank problem typically sheathing problems are isolated to small areas but old plank sheathing presents more of a challenge. After the 1960s the predominant residential roofing substrate became 1 2 cdx plywood. Over time shiplap fir wood resin dissipates causing the boards to shrink crack form knot holes and become extremely brittle. These 8 to 12 inch wide boards were nailed together tight.

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. In that case they could whe replacing shingles fill the larger gaps with firring. Plywood used for roof decking is typically called sheathing and carries a grade stamp indicating its load and span ratings and other performance factors. 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.

The issue guertin explains is the gaps between boards. Most western washington residential homes during this time were built with shiplap roof decks rather than plywood.