Elements of a Roof: Step One – Sheathing

Written by Ashlee on . Posted in Elements of a Roof

A roof contains several layers of different materials all applied in a specific way for a specific reason.

If you are looking to get a roof completed soon the process may seem rather daunting. The good news – you don’t have to know all the details of each and every layer, the roofer knows what he is doing. But it is nice to know what will be going on your roof so you can better understand what it is you are paying for.

In this series, we will detail each layer and the material that are used.

Step One – Sheathing

Once all original roofing materials are removed (which is a HUGE task itself) its time to inspect and replace necessary sheathing.

What is sheathing?

Sheathing is the wood material that the shingles and other roofing materials are applied to.

Sheathing has an important job. Not only do you apply the shingles to it, but it also holds the roof trusses in place and essentially holds the entire roof together. It provides all the necessary support to hold the weight of the entire roofing system, and anything else that is on the roof, like snow, people, etc.


What is sheathing made of?

There are a couple options for sheathing. The most common is Oriented strand board or OSB for short. OSB is a lightweight material, but is strong enough to withstand the weight of the roofing system plus some, without bending or breaking. OSB is cost effective making it the preferred choice for most roof types.

Plywood sheathing is also used, but more commonly on roofs that require much more weight to be supported. Roofs like slate or concrete are extremely heavy so plywood is used in those cases. Plywood is the more expensive option.


Why does my roof not have sheathing?

Wood shake roofs do not have plywood or OSB sheathing. Typically they have what is called Skip Sheathing. Which is widely spaced boards that run perpendicular to the roof trusses. Wood shake roofs require extra venting so the gaps help that. All other roof types should have your standard sheathing.


How do you quote sheathing?

Because sheathing is UNDER all the roofing materials, it is sometimes hard to tell if it is warped or damaged. Some damage can be seen from the attic space. Typically you can get a good idea by looking at the roof if the sheathing is damaged, but you can never be sure until you are face to face with it.


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