Rafters Vs Trusses

Rafters Vs Trusses: What Are The Differences?

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James
February 26, 2022
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When constructing a roof for your home, you might wonder if you should make use of rafters or trusses.

You’ve probably heard these terms used in the construction industry but maybe you don’t know what they really are or why they’re important. 

Aren’t rafters and trusses the same thing?

Although they are both roof supportive structures, and you will have to choose one over the other for your home, they do have different traits. 

So, although rafters and trusses are similar because they both are used for roof framing, they do have some important differences you should know about. This will ensure that you choose the most appropriate one for your home. 

What Is A Rafter? 

Rafters Vs Trusses

A roof rafter is a series of sloped structural wooden beams. These extend from the hip or ridge to the roof’s eave, wall plate, or downslope perimeter. A roof rafter essentially supports the entire roof system.

A rafter can be described as a framing method for the roof. The wood is inclined from a central ridge bean and it connects to the outer walls of the house. 

Rafter boards are used to create a roof slope, with 2x8s, 2x10s, and 2x12s being the most common sizes that are available. When you’re ready to put insulation into the roof, you will place it between the drywall and rafter boards. 

When a roof frame is built with rafters, this is called stick framing. Every rafter is built directly on the job site with lumber, which makes it convenient but it’s also a labor-intensive process. However, the benefit of this is that the rafter will be made immediately, depending on what is required for the roof construction. It can also speed up the construction process.

There are different types of rafters to know about. These include the following:

  • Principal rafters. These are large pieces that are installed on each side of the roof structure. 
  • Common rafters. These are smaller than principal rafters, and they get installed between the principal rafters.

When combined, both principal and common rafters provide effective structural support for the roof.

Less common rafters include the following:

  • Hip rafters. These rafters run from the building’s outside corners all the way to the ridge board. They are designed at a 45-degree angle. 
  • Auxiliary rafters. These are used in cases where the principal rafter requires extra support. 
  • Valley rafters. These are rafters that get installed at the home’s inside corners, also at a 45-degree angle. 
  • Compass rafters. These rafters are a little different. They are used for ornamental purposes because they are curved at the top and sometimes also at the bottom. 

Rafters: What Are The Pros And Cons? 

Pros 

  • Rafters give you more space in your home with the use of vaulted ceilings. 
  • Rafters are convenient because they’re built on the construction site. This also makes them a valuable idea for sheds, cabins, or other smaller building projects because you don’t have to wait for trusses to be produced in the factory.  
  • They can be used in locations that are difficult to reach.  

Cons 

  • Rafters are expensive as they can take a long time to build. You can expect a large residential roofing rafter to take up to a week to be built. 

What Is A Truss?

Rafters Vs Trusses

A truss is a wooden framework that also gives your roof more support. When compared to a rafter, a truss usually comes in prefabricated wood whereas a rafter is built on site. A truss is installed as a triangular webbing structure. It usually comes in 2x4s instead of wider dimensions.

A truss is usually made with steel plates in its joints which helps to lower labor costs as this prevents truss reinforcement from having to be completed on the construction site. A truss contains three main components:

  • Bottom chord – this is a horizontal beam. 
  • Top chord – this is made up of two boards that are angled up from the ends. 
  • Webbing – these are bracing boards or runners.

Pros 

  • Trusses are webbed, which gives them greater structural strength. 
  • You can build trusses yourself because they are purchased with instructions to make it easy to assemble them. 
  • They’re less costly than rafters. This is because they are built in a factory with machinery. Since building them is automated, trusses can be installed for less money than rafters. 
  • They take less time to build as small ones can be installed within a day or two.

Cons 

  • Assembled trusses are large so they are heavy and need to be delivered on a semi truck which will increase their shipping costs. 
  • Trusses have webbing that limits them when it comes to using the space above or beneath them. 

What Are The Main Differences Between Rafters And Trusses?

Rafters Vs Trusses

Now that we’ve looked at the pros and cons of rafters vs trusses, we can focus on their main differences.

  • Trusses are prefabricated, whereas rafters are built on site. 
  • Trusses have narrower dimension boards, which can make them less sturdy. 
  • While rafters contain two main outer beams to support the roof structure, trusses contain multiple beams. They can also be made in a variety of sizes and shapes to fit the building project. 

Which One Is Better For Heavy Loads? 

Both rafters and trusses are load bearing and they hold up to the elements well, but you still have to ask which one is stronger. 

It’s important to know how much weight you can hang from a truss or rafter. The minimum live load capacity of a rafter or roof truss for a non-sleeping area should be approximately 40 pounds per square foot. If it’s a sleeping area, it should be approximately 30 pounds per square foot.

However, trusses can handle more weight than rafters. This is because their design enables them to span a longer area and they’re webbed. They’re also made with braces that are placed strategically to further ensure the trusses can support a lot of weight.

Note that live load is a term that refers to a load that could change over time. The load weight is variable, or it could shift locations, such as if people are walking around in a home or building. 

Which One Should You Choose? 

Rafters Vs Trusses

Since trusses and rafters are so similar, you might not be sure if you should install one or the other.

You should choose rafters when you want a steeply-vaulted ceiling, you want to make use of the space in your home, such as by converting an attic into an office space; or it’s difficult for you to get your trusses to your building site without spending a lot of money.

On the other hand, a truss is a good choice if you can easily reach the building site and roof, and you want an affordable roofing system

How Much Do They Cost? 

While rafters are traditional roof frames, they do require roofers to have some skill and experience when installing them. This requirement can make their installation labor much costlier.

By comparison, trusses are prefabricated which means that they have to be delivered to the building location. Generally, trusses can cost between 30 and 50 percent less than rafters because of this feature. 

The average roof truss cost is between $50 and $450 per truss, or between $9 and $11 per square feet. Installing trusses on a 1,500 square foot roof will cost you approximately $13,500 to $16,500.

By comparison, rafters will cost an average of $7 to $16 per square feet, and installation costs $10,500 to $24,000, when installing them on a roof that’s 1,500 square feet. 

Are Rafters And Trusses Always Made Of Wood? 

Rafters Vs Trusses

There are usually three types of wood out of which trusses and rafters are made. These are fir, red cedar, and yellow pine. These can be strengthened by applying glue to them or by laminating thinner pieces that are glued together to produce a thicker beam.

Sometimes metal can be used, but metal costs more money and needs greater maintenance. It also can’t tolerate heat in the same way that wood can. Not every roofer is skilled when installing metal, which further makes it impractical.

There is such a thing as steel framing, but this is much more expensive – you’re looking at between $7 to $9 per board foot as compared to $3 to $5 per wood board. However, sometimes steel framing is required, such as if you’re building a very tall roof as the strong steel will give the building much more stability.

Rafters Vs Trusses: Which One Is Easier To Insulate? 

It is sometimes said that rafters are easy to insulate because you just have to install batts between each rafter. Batts are bulk insulation that is designed specifically to fit between studs, joists, and rafters.  

However, to increase the effectiveness of your insulation, you might consider using a layer of insulation above the rafters or inside the rafters.

When it comes to trusses, it’s a little trickier to figure out how to achieve effective insulation. If you have a flat ceiling in your home, you can use blown-in insulation. This is insulation that’s made out of materials such as fiberglass and cellulose. 

But, if you have scissor trusses, which are used to support a pitched roof, this type of insulation is not going to be as effective. An insulation installer will therefore have to be consulted so that you can get the most effective insulation for your home and roof design.

Despite the above, bear in mind that you don’t always have to insulate your rafters or trusses. You need to ask yourself what the space underneath the frame will be used for. If it’s going to be a living area, then it will benefit from having insulation to keep it comfortable. 

Can You Replace Rafters With Trusses? 

Rafters Vs Trusses

If you’d like to replace your rafters with trusses, this is possible but you need to consider various factors. The process will be labour-intensive, it requires the skills of a professional, and it will be expensive.

This is because you have to consider the load-bearing capacity of your specific roof. You will also require more support rafters and these will have to be added before you can remove the trusses, otherwise you won’t have enough support. 

You also have to consider that trusses have become more popular than rafters. In fact, they have slowly been replacing traditional rafters. Over 80 percent of new homes currently contain trusses instead of rafters to support their roofs, so they could be the better option.  

Related Questions 

What’s the difference between roof rafters and joists?

The only real difference between the two is that rafters provide more attic or storage space underneath them because insulation is fitted between individual rafters.

What, exactly, is a joist?

In roofing, a joist is a horizontal member that runs across a space It can be flat or pitched; concealed or exposed.

Conclusion 

Rafters vs trusses: which one is best?

If you’re not sure which one you should install in your home to give your roofing system more support, after reading this article you now have more information you need to make the best choice.

While there are some differences between rafters and trusses, trusses have become more popular in recent years because of their many advantages.

Sources:

James

James Weldon is a professional roofing contractor with many years of experience on the job. He does not only handle large projects and provide excellent services for his company’s many clients; James Weldon also dedicates his spare time to teaching others useful tricks of the trade. Using BuildCampus as an avenue to reach many roofers and aspiring roofing contractors, James Weldon continues to provide high-quality educational posts and buying recommendations for anyone who visits the website.