The Attic Structure of a Home

attic structures

The attic structure of a home is a place few people ever see. In general, most homeowners never look in their attic. Thus it becomes important our inspectors access the attic when performing a home inspection. Let’s look at some common aspects of the attic structure.

Cedar Shakes

Many houses built in the 1950s and earlier originally had cedar shake roofs. Cedar roofs are generally no longer allowed in the Los Angeles area due to they can easily catch fire. The construction consists of boards that are evenly placed out (commonly called skip sheeting) and then the cedar is nailed to the boards.

To meet modern codes, the cedar should be removed and replaced with plywood or OSB, and then new shingles should be installed on top of the new wood. However, sometimes, to save money, people will install new shingles right over the cedar. The cedar is still visible in the attic. This will be called out in the report, as the next time the roof shingles are replaced, the cedar will have to be removed and plywood or OSB will have to be installed.

Cedar shakes visible from the attic
Cedar shakes visible from the attic

Plywood/OSB Over Skip Sheeting

If the cedar is properly removed, it should be replaced with plywood or OSB. One common thing we see is water stains on the skip sheeting. However, if the plywood or OSB placed over the boards is free of stains, then we know the stains were from BEFORE the last roof replacement, and are no longer a concern.

OSB over skip sheeting in an attic
Note the stain is on the inner old board, while the newer outer board is not stained.

Standard Traditional Attic

The standard traditional attic structure has several variations, depending on the size of the home. These have been common building methods from the early days of housing and can still be found in custom new homes.

Standard attic
Typical standard attic construction. Note the stains indicating past leaks. 
Another standard attic construction type
Another standard attic construction type

Engineered Truss

Engineered truss systems were invented in the 1950s. We started seeing them in Southen Cariformoa homes around the 1980s. Nearly every home built since 2000 has an engineered truss system.

A truss system is designed by an engineer using triangle forms to use as little wood as possible. By reducing the amount of wood needed, a builder can build houses more efficiently. Trusses are usually built offsite in large numbers and then trucked in. The builder will then use a crane to lift the truss on top of the home.

Attic Engineered truss
Engineered truss

Because trusses are engineered to use just the right amount of wood, any break in the truss system is a significant defect.

An exception is a horizontal brace, usually a 2.x4 that connected the individual trusses together. It is just for support when loading the trusses up onto the top of the home. Afterward, the horizontal brace may be removed, cut, or simply left in place.

A tighter truss system
A tighter truss system.

Read additional articles about attics:

Bed Duct work that may in your attic. 

Worn roofs vs leaking roofs

Who’s looking in the attic 

To book your home inspection, call 818-298-3405 or book online here.