What Is A Roof Deck?
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What Is A Roof Deck?

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Posted By: Roof Troopers

A roof deck is a wooden underlayment under the home’s roofing system.

In Northern Virginia, most roof decks are either wood strips, OSB, or plywood. The thickness varies depending on when the home was built and what the codes were at that time.

Wood Strips

A wooden strip is exactly what it sounds like. It is a piece of wood that is commonly a (1”x 6”). You’ll find this on most older homes.


Oriented Strand Board, also known as OSB, is the most common material used today in residential buildings in Northern Virginia. OSB is actually a mixture of long strips of wood that is strategically placed, then dried, and treated with wax and binders. They are grouped into big sheets and pressurized at a high temperature.


Plywood is made from long knife peels off a thin layer of wood that is dried, with several layers of veneers put together with the grain direction alternating between layers. Glue is used between the layers and the stack is heated and pressed to form the panel

Thickness of Deck

As mentioned before, the year your home was built will likely determine the type of roof deck you have and its thickness.

Older homes with OSB or plywood may have 3/8th of an inch thickness, while newer homes may have either be 7/16”, ½” or at times even ¾” of an inch thickness.

If your roof deck is 3/8th thick and you have multiple rotten roof deck boards, instead of replacing it with the same thickness, we recommend upgrading it to 7/16” boards. Which will be more structurally sound.

If your home has wooden strips. It is common to install the entire roof deck with OSB boards, especially if the wooden strips are rotten.

Whether you are using OSB or plywood boards, you need to make sure there is a ⅛” gap between the boards. This allows for boards to expand and contract without buckling. This is done by putting clips between the boards which are coded in most, if not all areas. If done correctly, these clips can be seen from the attic when reviewed closely.

Why Are Roof Decks Important?

The roof deck is the initial step and plays an essential part in having a long-lasting roof. Before the roof system is installed, the deck should be dry. Call our professional team at Roof Troopers for more information.


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