Plywood Over Plank Roof

Personally i like plank spaced decking.

Plywood over plank roof.

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. 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.

After the 1960s the predominant residential roofing substrate became 1 2 cdx plywood. The keyword here is solid it used to be standard to use shiplap 1 boards tongue groove or other boards for the roof deck. These 8 to 12 inch wide boards were nailed together tight. Most western washington residential homes during this time were built with shiplap roof decks rather than plywood.

Use decking screws to secure squeaking planks through 1 4 ply to joists. On older homes planks were often spaced for wood or slate roofs with wider exposures than the standard 5 inch tab on asphalt shingles. Its really common here too to see 3 8 plywood used on roofs from the 70 s. 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.

Today a shiplap roof is usually 60 years old. This is particularly important if your old sub floor has lumps and bumps in it. Over time shiplap fir wood resin dissipates causing the boards to shrink crack form knot holes and become extremely brittle. 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.

Take time to make sure your existing planks are well secured in place. Repair any broken planks. 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 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. 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. Install a layer of at least or preferably 5 8 ply over the existing planks.

But the spacing should not be more than quarter inch. Plywood is layers of wood plywood is made.