Roofing Plywood Over Boards

If your home was built before 1970 there is an excellent chance that your roof is going to have board sheathing in place.

Roofing plywood over boards.

It can withstand moisture for a brief period of time but may become warped and delaminated with consistent exposure to the elements. After the original roofing is removed what you will want to do first is look for bad pieces of. If your home was built prior to 1970 there is a good chance it will have board sheathing. Over time shiplap fir wood resin dissipates causing the boards to shrink crack form knot holes and become extremely brittle.

This particular type of plywood is crafted from layers of wood stacked on top of one another with alternating grain patterns in each layer. Applying the underlayment and the slip sheet. How to install metal roofing over plywood inspect your plywood. Plywood used for roof decking is typically called sheathing and.

If the old plywood had been removed. Most metal roofs will also require underlayment as well as a slip sheet. If the roofing underlayment is applied directly on top of the shiplap it will sag into the spaces and eventually leak. Today a shiplap roof is usually 60 years old.

Cdx plywood is a construction grade type of plywood that is designed for exposure to the elements. As the boards to do the roof deck were manufactured here in the northwest it was still more economical than plywood through the 60s. 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.

After the 1960s the predominant residential roofing substrate became 1 2 cdx plywood. Open spaces form between the once tightly fitted shiplap 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. The most common materials for this are oriented strand board osb or plywood both formed of layers of wood bonded into a panel.