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What Are Roof Trusses? | 2024 Guide

By Amanda Lutz Updated August 6, 2024

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Your roof’s design plays a major role in the layout of your home, its structural integrity, and the materials you can use to build your roof. A roof truss is one essential component used in building and supporting roofs throughout the United States. This structural framework connects the space above a room and provides support and strength for your roof.

Whether you’re preparing to build your own home or want to learn more about the structural integrity of your current home, this guide will help you navigate the advantages of roof trusses, common alternatives to roof trusses, how much this framework costs, and different truss styles for a safe and sound roof.

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Understanding Roof Trusses

A roof truss is a prefabricated structural framework that builders can install on top of an in-progress home to support the roofing materials and give the roof its final shape. It looks like a hollow triangle with an array of lines and triangles within a larger frame. 

The wood pieces descending from the top peak are called the top chords, and the wooden pieces running along the bottom are the bottom chords. The pieces are connected by nail plates or web ties, and there are wooden webs or webbing running through the triangle—all of these smaller internal supports strengthen the entire triangle so it can support sheathing, shingles, tiles, and even solar panels.

Different trusses will have distinct webbing structures designed to provide varying levels of strength or give the roof a particular shape.

Roof trusses are installed on the home’s framing down the length of the home. Builders will lay out a series of roof trusses, standing them upright and securing them to the exterior walls at regular intervals. As the home build continues, builders will attach sheathing, underlayment, and the roof on top.

Here are the main benefits of roof trusses:

• They’re prefabricated, which streamlines the construction process.
• Truss engineers can use a wider variety of assembly and build methods in the factory, so attic trusses can come in many different designs to support architectural plans with varied living spaces.
• Trusses are one of the most cost-effective ways to build and support a roof structure.

Trusses offer superior structural integrity. Each triangular web is structurally sound and unlikely to break or come apart over time. They also reinforce the home’s overall structure because they tie the exterior walls into a fixed position rather than simply resting on them.

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Types of Roof Trusses

There are a variety of roof trusses that give roofs their form. The shape of the exterior triangle and the composition of the wooden webbing inside the truss are two factors that can affect a roof’s form and support. Some of the most common types of roof trusses include fink trusses, gambrel trusses, and scissor trusses.

Fink Truss

A fink truss has a diagonal web arranged in a “V” shape and a structural system that spans long distances. Its design can support steep inclines and heavy materials, but it can also limit the use of attic space. This type of truss is commonly found in residential homes and bridge architecture, but it also can be seen in barns and garages.

Gambrel Truss

Most commonly used in barns, a gambrel truss is a tall truss that supports a wide span and can add to the vertical space in a building. It has two slopes that descend on both sides of a peak, providing additional storage in your roof without taking up additional space. A few disadvantages to a gambrel truss is that it’s more susceptible to collapse and isn’t great for areas that experience heavy rain or snowfall.

King Post Truss

A king post truss has a simple design of two triangles that form the base and a diamond configuration with a vertical frame that forms the top and middle. The central vertical post is called the “king post,” giving the truss its name. These trusses extend up to 26 feet across and can help disperse the load of a roof. Their simple design also makes them one of the most cost-effective roof trusses available.

However, its limited span doesn’t make the king post truss suitable for larger buildings or homes. In fact, king post trusses are typically found in older homes and are used for building small homes.

Queen Post Truss

A queen post truss differs from a king post truss in that it has two vertical posts instead of one central vertical post. This type of truss can be much larger than king post trusses, with a length of up to 40 feet, making it better for longer spans. This type of truss provides a lot of support for mid-sized homes and sheds.

Scissor Truss

A scissor truss, also called a vaulted truss or cathedral truss, is an A-frame structure that connects two triangular legs with a top beam. This type of truss supports pitched roofs, where a raised or vaulted ceiling is desired. While scissor trusses are easy to install and have a low installation cost, they’re difficult to insulate and provide narrow access at the eaves, making it hard to perform roof repairs.

Other types of trusses with varying levels of complexity include the double fink truss for large homes, flat trusses for commercial buildings, and mono trusses for roof extensions.

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Roof Truss vs. Roof Rafter

Roof rafters are a popular alternative to trusses. These wooden beams slope downward from the central ridge or hip of the roof down to the top of the wall, where a series of ridge boards (or ridge beams) and ceiling joists hold the rafters in place. Rafters are measured, cut, and arranged on-site rather than being prefabricated at an off-site factory and transported to the build site.

Here are some of the advantages of choosing this stick-frame roof construction method:

• Allows for more flexibility: If you’re designing a custom home with trusses, you have to finalize all design decisions before you order the roof trusses. You won’t be able to change your mind later without delays and added expenses. With a stick-framed design, you can change your mind up to the last minute without significant delays. This gives you more freedom regarding the type of roof you have.
• Creates convertible attic space: Most trusses are shaped like triangles with wooden webbing across the middle. This design makes it hard to create livable space in your attic. Rafters have sloped beams, so they allow you to convert your attic into a bedroom or office. You can even have high, vaulted ceilings underneath your rafters if you renovate your home and remove the empty attic space entirely.
• Is easier to install insulation: Installing insulation in your attic is a simple and cost-effective way to reduce your home’s energy consumption. With rafters, it’s easy to install the insulation, inspect it, and add more insulation over time.

While rafters have some advantages over trusses, some of these conveniences come at a cost. Rafters cost more to build and install than trusses, and they take more time to install because all the work happens at the building site. They don’t offer the same durability as trusses, and because trusses are becoming more popular, it’s also harder to find contractors who specialize in high-quality rafter design.

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Roof Truss vs. Joist

A joist is a horizontal beam that provides structural support and prevents the “A” shape in a roof rafter from twisting and falling. Builders add joists to rafters through collars and metal fasteners. Joists are placed along the ceiling, run horizontally to connect a series of parallel rafters, or bear weight as part of a ceiling or floor (or both, in an attic).

Joists are a good option if you have a stick-frame roof and want the option to modify the structure later. Compared to trusses, attic spaces defined by joists are simpler to renovate and restructure.

Joists do have some limitations. They handle a lot of structural load, so they can’t have defects or be joined from multiple pieces of wood; they can be only as tall or strong as the tree they came from. Builders also can’t drill holes or notches into joists because that compromises their structural integrity. As a result, roof trusses are often a better option for larger structures or very heavy roof materials.

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Roof Truss Cost Factors

Roof trusses are a cost-effective alternative to traditional rafter and joist-based roofing. However, there are a variety of factors—from your building time line to the truss materials used—that can affect the overall cost of your project. Consider the following cost factors to plan your project accordingly:

• Design: Using simpler, standardized truss designs will cost less than using custom trusses. However, both options are typically more cost-effective than using on-site rafters.
• Labor costs: Trusses typically require specialized equipment and professional expertise to install correctly. These labor costs will ultimately depend on the size of your roof, the type of roof truss you’re installing, and the truss material used.
• Materials: Builders can use either wood or metal to build trusses. Metal is the costlier option, but it can provide longer-lasting structural support.
• Size and pitch: Bigger roofs will require more materials, and their shape can be more structurally complex, which can increase the cost of installation.
• Time line: Roof trusses are fabricated before being transported to the build site. Finalizing the truss design and ordering in advance can save you money, whereas rushed orders will cost more.
• Transportation: Completed trusses must be transported to the construction site and are bulkier to move than simple wooden beams, adding additional costs to the installation.
• Truss type: The material, size, pitch, and shape all determine the type of truss you can use. The more complex the truss is, or the more material it uses, the more expensive it will be.
• Waste removal: Roof trusses are made to order and delivered right to the build site. They cause less on-site waste than rafters and joists, which are cut and assembled on-site.

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How to Save on Roof Truss Costs

The average cost of a new roof truss is $21,000,* with prices ranging from $7,500–$35,000 for most home construction projects. However, there are some steps you can take to reduce the cost of a truss system. Consider these factors to help you save on your roof truss installation:

• Choose standard trusses: Commonly used trusses will be more cost effective than custom designs.
• Install the roof yourself: If you’re building a do-it-yourself (DIY) shed or stand-alone garage, consider installing the trusses yourself to save on labor. We recommend hiring a contractor for homes and large buildings where slip and fall accidents can be more severe.
• Negotiate with suppliers: Some suppliers may be willing to give you a bulk discount depending on how many trusses your project needs and the time of year the installation occurs. Consider comparing rates from at least three different roofing contractors before making a final decision.

*All cost data in this section via Angi.

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Our Recommendation

Roof trusses are an essential part of building a new home or modifying a roof on an existing property. They can support roofs on various homes and are a cost-effective way to offer structural integrity. Before you begin your roofing project, we recommend contacting an experienced roofing contractor who can help you assess your roof truss needs and make the right choice for your home.

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Roof Trusses FAQ