Why is it that almost 80% of modern roofs use trusses? Before we answer this question, let’s start from the beginning. Roofs are an essential element of your home’s structure. They protect you from all types of weather and also give your home an aesthetic appeal both on the inside and outside. But how are roofs actually built? There are two types of systems to support a roof: rafters or trusses. In this article, we will discuss the difference between these two types of systems, comparing their overall cost, design, and durability. And of course answer the question of why trusses are the modern choice for new construction.
What Are Rafters?
Rafters are sloped wooden beams extending from the roof ridge (top edge of the roof) to the perimeter wall plate, forming the skeleton of the roof structure. Each rafter supports the weight of the shingles on top of it and transfers that weight to the outside walls. These structural timbers are cut and assembled on-site by skilled carpenters.
Materials
Rafters are typically made of wood but can also be made of steel and other materials. Softwoods like cedar, pine, and spruce are generally the choice of wood used to make rafters as these woods are lightweight, flexible, and affordable. Rafters are commonly built using 2x8s, 2x10s, or even larger lumber for strength, depending on the project.
Applications
Rafters have a long history in the construction industry as one of the oldest methods of supporting roofs. Rafters were the original way to build a roof. Notably, rafters are used in homes with vaulted ceilings, and typically those with a large attic space.
Pros of Rafters
Rafters come with several advantages, especially in terms of customization and flexibility. Here are some of the benefits rafters offer over trusses.
Design Flexibility
Rafters allow for creativity during construction because they can be customized to various pitches and shapes. The flexibility allows builders to make unique roofs, specific to the demands and preferences of the owner.
Attic Space
Due to their ability to support higher roofs without obstructions, you can create a large, usable attic space for either storage or living. such as a loft.
On-Site Customization
On-site adjustments to the height, pitch, span, and shape of the roof can be made to correct unforeseen construction demands. As the construction is ongoing, rafters can be cut, bent, and manipulated to achieve the desired results, making them a great choice for complex roof designs.
Cons of Rafters
While rafters offer several advantages, they also come with disadvantages.
Requires highly skilled labor
Because rafters require a lot of joining, they need skilled professionals who can cut the rafters precisely to achieve the specific design. Doing it yourself or working with unskilled laborers may result in serious structural issues.
Vulnerable to weather delays
As building rafters is an outdoor project that takes considerable time, changes in weather can delay the project. Rain or strong winds may force the crew to stop working as continuing in inclement weather is dangerous and could cause injury. In this way, the progress of rafter construction is at the whim of the weather.
What Are Roof Trusses?
Trusses are prefabricated triangular frames made using timber or steel to support the roof and distribute its weight to the outside walls. They are built in a controlled factory environment and professionally transported to the construction site. Because they come ready to fit and secure, trusses make the on-site construction process easier and faster.
Design Variations
Trusses come in various designs to make different types of roofs. Depending on your design, aesthetic style, and desired energy efficiency, there is a truss type that fits your needs. If you are looking for a truss that allows attic storage space, you can choose a spread web or a scissor truss. If you are looking to create an entire room in the attic, go for the gable or gambrel design.
Consistency
Just like other factory-made fabrications, trusses are engineered to look consistent and offer the same quality in every piece. Thanks to controlled production, factories can produce whatever roof designs you like, in bulk, at an economic price. It’s these features being uniformity, design options, and economical pricing that makes trusses such a popular choice for roofing projects.
Pros of Trusses
Most homes in America use roof trusses because they have many advantages during and after construction process:
Cost-Effectiveness
Trusses are more affordable for roofing because they are prefabricated for specific roofing styles. This reduces material waste and lowers the costs of construction.
Faster Installation
For a rafter project that would take a week to build, it takes only a day with trusses. The quick turnaround is because most of the work has already been done in the factory. The on-site laborers just need to fit and secure the structures instead of measuring, shaping, cutting, mounting, and adjusting the timber if it were a rafter home.
Structural Efficiency
Another benefit of trusses is their ability to support long spans without additional load-bearing walls. The maximum a rafter can span is 30 ft without supports. A truss on the other hand can go up to 60 feet. Having no need for obtrusive supporting walls allows for the maximum interior space under the roof. In addition, as there are no load bearing walls, modification of the locations of the interior walls is easy and does not require an engineer or architect.
Cons of Trusses
Reduced Flexibility
One of the biggest limitations of trusses is their fixed design, which makes on-site customization difficult. Trusses are pre-built and delivered in specific designs, so there is no possibility to make on-site adjustments during construction.
Logistics Challenges
Unlike rafters, whose materials only require a standard truck, trusses require specialized transportation and equipment such as forklifts and cranes to actually place the trusses on the outside walls. In addition to transport, there can often be delays in the manufacturing of the trusses at the factory with wait times coming to almost 1-2 months. Although trusses are fast for installation, waiting for the factory may be even longer than building rafters from scratch.
Side-by-Side Comparison
Feature | Rafters | Trusses |
| Installation | On-site assembly | Prefabricated and quick to install |
| Material Use | Larger lumber; more waste | Lightweight; minimal waste |
| Cost | Higher labor and material costs | More affordable overall |
| Flexibility | High customization options | Limited to prefabricated designs |
| Durability | Strong, traditional framing | High strength with webbing design |
Why Roof Trusses Are Often Preferred
Roof trusses are the preferred choice for modern homeowners for many reasons.
Cost Efficiency
Trusses are up to 50% cheaper than rafters when accounting for labor and materials. That’s because trusses are prefabricated and are easier to install, with no material waste at the construction proceeds.
Faster Installation
Unlike rafters that are assembled on site, trusses are pre-made for the project, making the installation faster. For a standard home, the whole truss roof structure will only take a day to install.
Structural Strength
Trusses are arranged to form a web-like structure that distributes weight evenly to the walls around them. This construction method enhances its load-bearing capabilities making them a more durable choice.
Compatibility with Modern Designs
Open concept designs are a staple of modern construction styles. Using trusses allows for complete flexibility of the interior space as no load-bearing walls are needed.
When Rafters Are the Better Choice
Rafters can be a great choice for homeowners for a variety of specific reasons.
Remote or Challenging Locations
If you live in a remote location that’s challenging for large industrial equipment to access, rafters are a better choice as they are easier to transport. No special equipment is needed, only a simple truck, to move the timber from one place to another, making the logistics easier for a project using rafters.
Architectural Flexibility
Custom roofs reflect the unique style of the homeowner and this can be achieved more easily with rafters. Because rafters are made on the construction site, it’s easy to make adjustments to find the desired look. This option is the best for constructing intricate rooflines and vaulted ceilings.
Attic Space
If you are looking to have an extra space in your home above your main living quarters, rafters allow for this flexibility. Rafters are simply single beams that go from the ridgeline to the perimeter wall plate, allowing for maximal space underneath. The intricate webbing of a truss system takes up this space, making rafters the choice for individuals wanting to have a functional attic in their home.
Vaulted Ceilings
If you want to have the flexibility of having vaulted ceilings in your home, you have to use rafters. Trusses employ latticework which distributes the load of the roof but eliminates the possibility of having a vaulted ceiling. Rafters on the other hand are simply beams going from the roof’s top ridge to the wall, with no lattices, thus making the structure of a vaulted ceiling. Along with a vaulted ceiling, you can install a skylight. This is not possible with trusses.
Your Project
When making a decision between rafters and trusses, consider factors like your design goals, budget, location challenges, and construction timeline. Rafters are ideal for custom roofing designs and are more adaptable to remote and complex construction sites. On the other hand, trusses are a perfect choice if you are on a tight budget and want your project to end in a short period of time. If you are in need of a new roof and want a professional’s opinion, call us at Lumina Construction, at 212-920-9163.