Plywood Over Old Roof

Its really common here too to see 3 8 plywood used on roofs from the 70 s.

Plywood over old roof.

But with the old plywood left in place it will be considerably more difficult to locate the rafters to ensure proper nail. As the boards to do the roof deck were manufactured here in the northwest it was still more economical than plywood through the 60s. Both cdx plywood and osb tend to come in standard sheets of four foot by eight foot 4 8. However you might find that osb can better suit your needs than plywood for the roof.

Open spaces form between the once tightly fitted shiplap boards. If the old plywood had been removed. Fortunately this is one issue that has primarily been standardized by the industry. The new plywood will have to be nailed to the rafters or roof trusses.

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. 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. 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.

Exterior grade plywood was not available until the 1940 s. Today a shiplap roof is usually 60 years old. If your home was built prior to 1970 there is a good chance it will have board sheathing.