The roof is arguably the most important component of a house. After all, it is what protects everything inside from the elements.

And whatever material your roof is made of is ultimately held up by the roof deck (also known as roof sheathing), making it one of the most critical parts of any building.

What even is roof decking?

Roof decking, also called sheathing or substrate, is a layer of wood paneling that supports the shingles, tiles or whatever roofing materials are on your roof. The sheathing is fastened to the roof’s joists and trusses, and then the shingles are nailed down to the sheathing. Sheathing supports the rest of the roof and acts as a last line of protection from the elements. Because sheathing is a wooden product, it is subject to water damage and dry rot if kept in a humid environment. Replacing the sheathing on your roof can get expensive if there is extensive damage, so make sure to inspect your attic regularly to make sure things are dry and sound. 

If you have a tile or wood shake roof and are looking to replace it, you may have to get new plywood installed if you don’t already have it. Oftentimes on those roof types there is a type of sheathing called “skip-sheathing” which many roofers will not install on top of.

What does roof sheathing do? 

  1. Supports shingles/tiles

Sheathing makes up the base of your roof. It literally holds up the shingles or tiles or whatever material your roof is made out of. These materials are fastened to the sheathing with either nails, staples, or screws.

  1. Prevent leaks

Sheathing prevents leaks by providing a smooth, solid surface that holds up the waterproof underlayment that protects against moisture penetration. 

  1. Prevents wind damage and blow-off

A good solid roof deck will act as a steadfast anchor to secure your roof during storms and other high wind events.

  1. Strengthens roof structure

The roof deck spreads the load of the roofing material evenly over the roof joists. The deck makes it easy to walk on your roof without fear of falling through the roof.

  1. Makes future roof work easier

Having a solid roof deck makes it much easier for contractors to replace your roof in the future or install other equipment on your roof such as solar panels.

What is roof sheathing made of?

Roof sheathing can be made of a number of different materials, but most commonly it is 7/16” OSB plywood. This is a standard roofing and construction material that can be found all over the country.

Other forms of sheathing include board sheathing, which is something like 1×8 or 1×12 boards that are fastened down on top of the roof joists. 


Another common form of sheathing is skip-sheathing. Skip-sheathing is more common for roofs constructed with tiles or wooden shakes, and basically just leaves a large gap between the boards where the tiles or shakes would be floating anyway. Skip-sheathing is designed to save materials costs and improve the ventilation of a roof, but it comes with some serious drawbacks, the biggest one being the inability to install other roof types or solar panels. Asphalt shingles require a solid deck to be nailed into, and skip-sheathing just won’t cut it, not to mention the hassle of walking on spaced out boards for the roof installers. Also, solar panels need a solid deck to be mounted on top of, and therefore won’t typically be installed on skip-sheathing. If you have skip-sheathing on your house right now and are looking to get a roof replacement or get solar installed, you will almost certainly need to have plywood installed. Wondering how to check what type of sheathing you have? Click here to find out.

When do you need to replace the roof sheathing?

  • If you are experiencing leaking from your roof or can see moisture/water damage
  • If you see the wood is rotted. Dry rot can cause serious damage to wooden structures, and must be removed and replaced with new materials when it is encountered.
  • If you have skip-sheathing. If you are replacing your roof or planning on installing solar panels, it is recommended that you replace any skip-sheathing with a solid deck of 7/16” OSB or plywood.
  • If your roof is sagging. A sagging roof can be a symptom of sheathing that has lost its structural integrity. If your roof is beginning to sag, it is a good idea to take a look in the attic and see if there is excess moisture or rotting in the sheathing or roof joists.

If you have a roof with any of these issues, it is recommended that you speak with a roofing professional to discuss your options and to see if replacing your roof is necessary. As a preliminary step, we recommend inspecting your attic annually to assess the condition of sheathing of your roof. To do so, go into your attic with a flashlight and take a look at the plywood boards and roof joists for any damage or moisture.

To see how much it would cost to replace your roof, visit to receive free estimates from a number of installers in your area.