Rafter parts

Rafter parts
Video Rafter parts

You’ll be evaluating the roof framing from inside the attic space, but we have an advantage in technology. Let’s strip away the roof and wall coverings of a home and identify some of the more common roof framing members. We’ll start with a conventionally framed roof in which individual roof-framing members are cut and assembled on-site.

Conventional Roof Framing

Common Rafters

Rafters which rest on the outside walls at the bottom and connect to the ridge at the top are called “common rafters” (highlighted here in yellow).

Read more: How to fix a broken rafter

Rafters on opposite sides of the ridge should be installed directly opposite each other in pairs – although, if you see a few that don’t align, it’s really not a defect. Rafters sometimes have to be moved a little to accommodate components of other home systems. The illustration above shows a rafter moved to accommodate a combustion vent.

If you see many rafters that don’t align, you may comment on this, but in existing homes, refrain from calling it a defect unless you see failure. In newer homes, many rafters which don’t oppose usually indicate poor-quality framing. It’s an indication that you should look carefully for other problems in the roof framing.

Rafters are typically installed on 24-inch centers. If you see rafters installed on centers greater than 24 inches, look for signs of failure, such as sagging of the rafters. If you see sagging rafters, recommend stabilization by a qualified contractor. Stabilization typically involves installation of a purlin system.

Hips

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Hip roofs have “hip rafters” which are oriented diagonally to the ridge and outside walls. Hip rafters are simply called “hips,” and are shown here as brown. Hips rest on an outside corner at the bottom and connect to the ridge at the peak.

Rafters which rest on the exterior walls at the bottom and connect to a hip at the top are called “hip jacks,” shown here as purple.

The purpose of the ridge is to provide an easy method for connecting rafters at the peak of the roof, and to provide better nailing at the peak.

Read more: Attach rafter to ridge beam

Older homes may have no ridge at all. That was a common building practice at one point in various parts of North America, and it’s not a defect as long as the rafters oppose each other.

Engineered lumber used for roof framing has very specific requirements for connections, and discussing them here exceeds the scope of this series. The manufacturers of metal connectors for engineered lumber publish connection specifications in their catalogues and on their websites.

In older homes in some areas, it’s common to find no strongbacks. It’s a quality issue unless the roof is sagging; then, it’s a structural issue and you should recommend stabilization by a qualified contractor.

The term “purlin” has several different meanings depending on what part of North America you’re in, what part of the roof you’re talking about, and the background of the person you’re discussing it with, so don’t be surprised if someone tries to correct you.

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