New Plywood On Top Of Old Plywood On Roof

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.

New plywood on top of old plywood on roof.

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. 5 8 inch 26 87 per sheet. Here is approximately how much different options cost. The most common scenario is a home that has rafters set approximately 16 inches apart.

Roof decks on homes built before 1970 are often 1 8 fir pre plywood shiplap. This means that you must replace old roofing plywood. One reason often cited by contractors to justify adding a layer of plywood to an existing roof structure is the presence of old style board sheathing. Until the 1940s exterior grade plywood was not available.

Chances are the shingles on your roof were attached on top of a plywood base. A local competitor never strips the old roof when installing a new metal roof and we ve pointed out to prospects that i w will not stick to the old roof. 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. 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.

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. The answer depends mostly on how far apart the rafters are and the roof loads which vary based on the pitch of your roof. But with the old plywood left in place it will be considerably more difficult to locate the rafters to ensure proper nail.

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.