What Are Roof Rafters? Their Role & Main Types

several wooden beams supporting a roof

As a property owner, you may be well-aware of how important your roof is to the protection of your property. It plays a role in curb appeal, energy efficiency and other critical aspects. While you may only see the outermost material on your roof, such as metal panels or asphalt shingles, the roof is actually comprised of several layers. One of the lowest layers in the roof structure are the rafters. It is important to understand what roof rafters are and how they work if you want to properly care for your property over the years.

What Are Roof Rafters?

Roof rafters are essentially the base or the frame of the roof. In construction, the rafters are installed approximately every one to four feet apart, depending on the type of roof that will be installed. These are typically laid at an incline, and they may be fastened to the top of the wall and run up to the apex of the structure, which is known as the roof ridge. In many cases, the rafters hang a foot or two over the edge of the property to create the eaves. This serves to protect the side of the building from unnecessary exposure to rain, sunlight and other damaging elements.

The upper layers of a roof can be very heavy, and the building must have the right support elements in place to hold the weight of the roof. Some materials, such as asphalt shingles, are significantly lighter than other materials. In some cases, such as when installing a heavy roof material like tiles, the rafters must be reinforced in order to bear the full weight of the roof. Roof rafters are commonly made out of wood or lumber in a residential building, but they may be made out of steel or other types of metal in a commercial building.

a representation of roof rafters on a white background

What Do Roof Rafters Do?

Support Structure for the Roof

Now that you know more about what roof rafters are, you may want to know what they do and why they are important. Because roof rafters are the primary support structure that holds your roof up, their strength and utility are critical to the overall condition of the property as well as to the lifespan of the roof itself. Generally, the closer the rafters are placed together, the stronger the base of the roof is. However, the strength of this area of the property is also determined by the material that is used and how the rafters are connected to the walls.

The Bone Structure of a Building

If you walk into the attic of your home or commercial building, you will be able to see the rafters. They are the bones of the building. Any weakness in the rafters will impact the overall condition of the roof and of the entire structure of the building. Therefore, you should take time to inspect your rafters periodically. In most cases, they will remain in good condition for decades. However, wood rot, termite damage, water damage and other issues can cause them to weaken.

When this happens, they should be replaced as quickly as possible. When you inspect the roof rafters, you should also look for any signs of moisture or water stains on them. This may indicate that the roof has a leak. It is not always possible to spot the signs of a leak from the exterior of the property. This means that inspecting the rafters is a good way to learn more about the condition of the roof.

wooden roof rafters on a ceiling

What Are the Main Types of Roof Rafters?

As you might imagine, there are several different types of roof rafters that you may find when inspecting the interior layers of your roof. Each serves a different purpose. Therefore, learning more about these rafter types can give you greater insight into the overall construction of your property.

#1. Common Rafters

The most prevalent type of rafter is a common rafter. You will find it in almost all types of residential and commercial roofs. This is the primary type of rafter that runs the length of the roof from the top of the wall, otherwise known as the plate, to the apex of the building. The apex is also known as the ridge. They provide the main support for the structure of the roof. Moreover, they also are necessary for the other types of rafters to function as needed.

#2. Hip Rafters

As the name may suggest, a hip rafter is a special type of roof rafter. It is located on the angular corners of the roof. They run from the corners of the walls on the side of the house up to the ridge line. Notably, however, they are only placed in the elevated corners of the roof and not in the valleys of the roof. These are the components that give most roofs their triangular appearance.

#3. Valley Rafters

Roofs are generally comprised of multiple planes. When the two planes intersect in a valley rather than in a pitch, a valley rafter provides the underlying support. Valley rafters are not located in all types of roofs. For example, if you have a four-sided home with a simple pitched roof, there are no low-lying intersections of roof planes. This means that there are no valley rafters in the roof design.

#4. Jack Rafters

Jack rafters is a broad term that actually describes several types of secondary supportive rafters. For example, a hip jack is a special rafter that runs from the hip rafter down to the wall plate. It is parallel to the common rafters in the roof design. A valley jack runs from the ridge down to the valley rafter. A cripple jack appears to be a common rafter at first glance. However, this unique rafter runs from a hip rafter to a valley rafter. It does not touch the ridge or the wall plate.

Bottom Line

As you can see, roof rafters are a rather complex system. It is well-designed to complete critical task of supporting the roof. Now that you are aware of its importance, take time to regularly inspect each rafter in your building to confirm its good condition.

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