Plywood Over Plank Roof

Open spaces form between the once tightly fitted shiplap boards.

Plywood over plank roof.

Most western washington residential homes during this time were built with shiplap roof decks rather than 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. On older homes planks were often spaced for wood or slate roofs with wider exposures than the standard 5 inch tab on asphalt shingles. This is particularly important if your old sub floor has lumps and bumps in it.

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. Plank sheathing usually 1 6 or 1 8 was used as a roof deck before plywood.

As roofing contractors in seattle we are often asked why do we need plywood over our old solid sheathing. In that case they could whe replacing shingles fill the larger gaps with firring. Its really common here too to see 3 8 plywood used on roofs from the 70 s. These 8 to 12 inch wide boards were nailed together tight.

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. Why re sheet over shiplap.

Over time shiplap fir wood resin dissipates causing the boards to shrink crack form knot holes and become extremely brittle. Take time to make sure your existing planks are well secured in place. Plywood used for roof decking is typically called sheathing and carries a grade stamp indicating its load and span ratings and other performance factors. Today a shiplap roof is usually 60 years old.

The plank problem typically sheathing problems are isolated to small areas but old plank sheathing presents more of a challenge. Repair any broken planks. Or they could place osb or plywood over current planking. The keyword here is solid it used to be standard to use shiplap 1 boards tongue groove or other boards for the roof deck.

The issue guertin explains is the gaps between boards. But the spacing should not be more than quarter inch.