New Plywood On Top Of Old Plywood On Roof

Chances are the shingles on your roof were attached on top of a plywood base.

New plywood on top of old plywood on roof.

But with the old plywood left in place it will be considerably more difficult to locate the rafters to ensure proper nail. This means that you must replace old roofing plywood. The most common scenario is a home that has rafters set approximately 16 inches apart. Here is approximately how much different options cost.

5 8 inch 26 87 per sheet. The answer depends mostly on how far apart the rafters are and the roof loads which vary based on the pitch of your roof. This is the best product to use because its very sturdy and high quality. While they don t prohibit installation over board sheathing asphalt shingle manufacturers do specify that the roof deck underneath must be smooth and tend to recommend plywood as the best option.

Roof decks on homes built before 1970 are often 1 8 fir pre plywood shiplap. Until the 1940s exterior grade plywood was not available. If the old plywood had been removed. Sometimes referred to as roof sheathing or a roof deck this plywood acts as a foundation for the layers of underlay and the shingles on your roof and connects the roof to the frame of the house.

Since the boards used for shiplap were manufactured here in the pacific northwest it was still cheaper than plywood up through the 1960s. Like most other things there is no one right answer for the plywood thickness of your roof. If there is water damage it will preform significantly better than the 1 2 plywood. So now they install 3 8 plywood over the top of whatever crap is in place so that the owner sees a new roof and they can stick the i w along the eaves and valleys and have it work.

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. The new plywood will have to be nailed to the rafters or roof trusses.