Should Use New Roof Decking Over Old Plywood Decking

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

Should use new roof decking over old plywood decking.

If the old plywood had been removed. Most western washington residential homes during this time were built with shiplap roof decks rather than plywood. Now the shingles are popping up moderate lumps. It can withstand moisture for a brief period of time but may become warped and delaminated with consistent exposure to the elements.

Its really common here too to see 3 8 plywood used on roofs from the 70 s. When updating a deck with new decking it s crucial that the old decking be removed so the joists and beams can be assessed and repaired if necessary. Is it ok to put new roof composition shingles over old shingles that were laid 25 years ago on new 3 4 plywood. Most construction sites will consider the use of either osb or plywood for the roof.

Cdx plywood is a construction grade type of plywood that is designed for exposure to the elements. One thing to consider is that the new plywood probably wants to be the same thickness as what would be used if it was used by itself on the rafters i e. 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.

It is cheaper to resheath the entire roof and go over it with asphalt shingles than to go over with new wood shingles. As roofing contractors in seattle we are often asked why do we need plywood over our old solid sheathing. The new plywood will have to be nailed to the rafters or roof trusses. The thickness of plywood used for roof decking depends on the roof slope the spacing of rafters and the weight of other material to be put over the decking as well as the design load the.

But with the old plywood left in place it will be considerably more difficult to locate the rafters to ensure proper nail. In the first half of the 20th century roofs in missouri were built with wood shingles over planks spaced about 1 apart. Installing decking over old decking will drastically reduce the lifespan of the material. 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.

If the old plywood was clean and not infested with dry rot or mold it should be ok to cover it with the new plywood. I have to hire a new roofer to fix what the first roofer messed up should i have metal roof taken off and replace e. Why re sheet over shiplap. These 8 to 12 inch wide boards were nailed together tight.

The joints between two materials will readily trap water in wet environments.