Plywood Over Plank Roof

The issue guertin explains is the gaps between boards.

Plywood over plank roof.

Plank sheathing usually 1 6 or 1 8 was used as a roof deck before plywood. Why re sheet over shiplap. As roofing contractors in seattle we are often asked why do we need plywood over our old solid sheathing. Today a shiplap roof is usually 60 years old.

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

Things to take into account when laying ply over plank subfloors. Personally i like plank spaced decking. Use decking screws to secure squeaking planks through 1 4 ply to joists. Its really common here too to see 3 8 plywood used on roofs from the 70 s.

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 keyword here is solid it used to be standard to use shiplap 1 boards tongue groove or other boards for the roof deck. Plywood is layers of wood plywood is made.

But the spacing should not be more than quarter inch. The plank problem typically sheathing problems are isolated to small areas but old plank sheathing presents more of a challenge. Over time shiplap fir wood resin dissipates causing the boards to shrink crack form knot holes and become extremely brittle. Or they could place osb or plywood over current planking.

In the first half of the 20th century roofs in missouri were built with wood shingles over planks spaced about 1 apart. Install a layer of at least or preferably 5 8 ply over the existing planks. After the 1960s the predominant residential roofing substrate became 1 2 cdx plywood. 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. On older homes planks were often spaced for wood or slate roofs with wider exposures than the standard 5 inch tab on asphalt shingles.