What Are Roof Trusses? Advantages and Disadvantages (AVOID This!)

Behind every successful roof is a supportive roof truss! Roofing is like icebergs in that there is much more going below the surface than what you can see. The roof’s structural components resist the vast forces that rain, wind, hail, and snow throw at them.


Roof trusses are robust, relatively lightweight economic structures that are designed to support the roof of a building. The roof trusses design spreads the forces applied to a home roof evenly through the truss, making them a more robust solution than roof rafters.

Roof Trusses Are Structural Components In A Roof

Roof trusses are triangles or other shaped structures installed over empty spaces below that support the roof. They provide the structural support necessary to keep the house roof strong enough to handle severe weather conditions.

Roof trusses are the most economical method of supporting rooves, and they are very long-lasting and durable.

Roof trusses are fabricated away from the building site and transported to the building as complete units.

Roof trusses are the modern substitute for roof rafters, and both have advantages and disadvantages.

What Are The Structural Advantages Of Roof Trusses?

The disadvantage of using single beams to support a load is that the part of the beam that carries the load is the only structural support provided.

Trusses are a whole structure made of multiple interlinking planks of wood. The shape of the truss is designed to spread the load force, which is applied at one point across the whole truss.

To understand this, let’s look at an analogy involving a bridge.

Roof trusses versus Roof Rafter

The older method of designing the roof structure was the use of roof rafters. Although roof trusses are being installed in more and more modern homes, a roof rafter may still be the optimal choice. The disadvantage of roof rafters is that the weight is less distributed and this can make them break faster.

To show the advantage of roof trusses, we can use the analogy of a car on a bridge. If the bridge is built with lengths of wooden beams and a car travels across the bridge span, the vertical force applied by the car’s wheels will be carried by the part of the beam the wheels are on. This means that the weight is more spread out and this makes the bridge stronger. The same is true about roofs that have trusses.

The benefits of the design of roof trusses are twofold.

  1. Because the whole load is spread across the entire rafter and not just a specific section, roof trusses provide more robust support for the structure.
  2. Once again, because roof trusses spread the load, lower strength wood can be used in the construction, resulting in a lower cost.

The table compares the pros and cons of each roofing structure.

The Pros And Cons Of Roof Trusses Against Rafters

Roof Trusses ProsRoof Rafters Pros
Roof trusses are strongerBecause Roof rafters consist of a single beam, they create more space in the roof area, allowing for an attic room to be included.
Trusses are easier to install, so they are a good option for a DIY buildBecause roof rafters are built on the worksite, more flexibility is available with their design.
Because Roof trusses spread the load over the whole frame and not a specific point, thinner wood can be used in their construction, and therefore they cost less.Roof trusses generally use 2 x 4 to 2 x 10 pieces of lumber.Roof rafters require minimum planning and forethought, so there is more leeway to change the roof’s design during the build phase.
Because they are fabricated offsite under factory-controlled conditions, roof trusses are built with more accuracy and smaller tolerances.It is easier to install ceiling insulation to help keep the temperature regulated in the home.
Roof trusses are manufactured on a factory production line and built faster than roof rafters.
Because roof rafters are delivered as prefabricated built-up units, they are easier and faster to install.
Because roof trusses spread the load, they don’t need interior wall supports along the length of the truss. It makes it easier for homeowners to take out interior walls in the future.
The Cons  Of Roof Trusses And Roof Rafters
Roof Truss ConsRoof Rafters Cons
Roof rafters are large, and they weigh a lot. They need a team of people, or a crane, to lift into place and install.Because Roof rafters cannot spread the load across the whole structure, higher quality wood is used, which increases the cost.Roof rafters commonly use 2 x 10 or 2 x 12 pieces of lumber
Because they are manufactured offsite, owners cannot change them to cater to the evolving requirements.Roof rafters are built on-site by the roofing specialist. Whereas roof trusses are built on a fast factory production line, each roof truss is hand-made and crafted specifically for the build. It means that roof rafters take longer to make and erect.
Because roof rafters take up more space, using them makes it very difficult to include an attic room in the building plans.
Roof trusses versus roof rafters

When Would You Use A Roof Truss System?

If you need to choose between roof trusses or rafters for your build, the following lists the considerations which will point you in one or the other direction.

A roof truss structure will be the most suitable.

  1. The budget is not unlimited, and the cost of the roof should be kept as low as possible.
  2. You don’t plan on using the roof attic for an attic room
  3. You are not looking for step vaulted ceilings.

A roof rafter system will be most suitable if

  1. You’d want the freedom to design a vaulted or a cathedral ceiling of your own choice.
  2. You intend to use the attic space as accommodation
  3. The cost of the build is less of an issue.


Roof trusses are the ideal solution for homes built off-plan, where cost is one of the chief criteria. Trusses provide more robust roof support, and because they are prefabricated offsite, there is a greater likelihood of better quality control.

Roof rafters give the homeowner greater flexibility when designing the house and provide access to the roof area to install an attic room. In addition, higher vaulted or cathedral-type ceilings are more easily incorporated into the home design.


Rafters vs Trusses (Pros & Cons and Design Guide)