Building a shed and wondering about the design and construction of its roof framing? You know that rafters are the traditional way of constructing a roof, but you’ve heard that trusses can make for a speedier roof-building process. So, what are the advantages of rafters vs. trusses for a shed?
Rafters provide more storage space and a wider variety of roof design options, while trusses offer strength and an easier installation process. Rafters are better for smaller sheds, while trusses are better for larger sheds since they are difficult to install on smaller buildings.
In this article, we’ll review the pros and cons of rafters and trusses and examine which method works best for the most popular shed roof styles to help you determine which is right for your shed.
What are Rafters?
Also known as stick framing, rafters are the traditional way roofs have been constructed on sheds and homes.
Rafters use angled rafter boards to connect exterior walls to what is known as the “ridge board,” which is the peak of the roof. Rafters are connected to walls via horizontal beams called ceiling joists. Rafter boards typically run past the external walls, creating soffits that aid with proper drainage.
For roof pitches with smaller slopes and greater overall spans, a ridge beam is used to support the rafters in place of a rafter board.
Ceiling joists provide the structure onto which a ceiling sits and prevents the rafters from spreading. Collar ties are used near the peak to prevent the rafter from separating from the ridge board.
Due to the smaller size of a shed structure, the construction of rafters is accomplished through the use of 2x4s and 2x6s.
One of the biggest advantages of rafters is the attic space they provide. The design of rafters allows for open space in the attic area.
Because of this, rafters are often used to make vaulted or cathedral ceilings in homes. For a shed, rafters offer additional space that can be used for storage.
Because rafters are built using stick framing, the roof can be constructed piece by piece without the installation of large pre-assembled pieces that can require extra hands. They also allow for customization of the roof design.
That said, there’s a good reason why rafters are no longer the preferred means of constructing a roof for homes. Because rafters must be built on site, they are more time-consuming to construct.
They also require precision. The use of a speed square to accurately measure angles is a requirement for rafter construction. Rafter construction requires accurate measurements and calculations that can be difficult for those lacking woodworking experience.
And while there are plenty of resources that can guide you through this process, keep in mind that the construction of rafters is dependent upon the specific dimensions of your shed.
Unless you’re following plans that match those dimensions, you will need to calculate the dimensions of the rafters yourself.
In addition to costing you more time to build, rafters will also cost you more money. The materials required for the construction of a rafter roof also make them generally more expensive than trusses.
What Are Trusses?
A truss is a framework of lumber that is designed to structurally support the space above a room while providing support for the roof.
Instead of using a ridge board with rafter boards, a common roof truss consists of two angled beams that create the roofline called top chords. A straight beam called a bottom chord creates the hypotenuse of this triangle, supporting the top chords at their base.
A beam called a king post runs from the center of the bottom chord to the peak of the top chords. Collar ties are replaced by truss webs, which are angled boards that run from the center of the bottom chord and base of the king post to the center of each top chord, providing additional support.
All of the boards are joined together through the use of metal gussets at each joint. Unlike rafters, which must be made on-site, roof trusses are prefabricated in a warehouse and then shipped to a job site for installation.
Build quality, strength, cost and time savings are the biggest pros that trusses have to offer. Because they are built in a warehouse using automated machines that make precision measurements and cuts, the quality of trusses are significantly higher than rafters that are built by hand on site. This means fewer mistakes in the construction of your roof.
What does all that webbing of beams get you? A lot of strength. That additional wood means a truss can span about twice the distance rafters can before needing extra support.
And because roof trusses are prefabricated, there is no need for time-consuming construction at the job site. Once a truss is delivered, it can be installed in a relatively short amount of time, allowing you to get your roof installed quickly and your shed weather-tight.
Even if you choose to build your trusses, achieving better quality and precision is easier with a truss. Truss construction can take place in the confines of your garage using jigs and a flat surface to ensure consistency and accuracy.
Trusses are also generally a cheaper option when compared to the cost of materials needed to construct rafters. Because trusses are pre-assembled, there is no waste from cutting. This advantage, of course, only exists with prefabricated trusses.
There are some notable cons to consider with roof trusses. Because they are pre-assembled, trusses require heavy lifting for installation.
Although your shed likely won’t require a crane for truss installation as a home would, the trusses on a shed are still heavy enough, and bulky enough to require at least a few extra pairs of hands for the installation.
And because their design requires a web of beams, trusses do not allow for open space in the ceiling area. This means no open ceiling or attic space for additional storage.
Prefabbed trusses for sheds are also generally only available in complete shed kits. So, if you’re building your shed from your design, you’ll need to construct your trusses. And once you’ve made those trusses, it is very difficult to alter your design later.
This may mean that if you want to use trusses to construct your roof, you might have to design and build them yourself, which eliminates the cost and time-saving pros we discussed earlier.
Rafters vs Trusses for Shed
Although there are similarities, the factors you need to consider when determining whether to use rafters or trusses for your shed roof can be quite different for a house than for a shed.
For one, you must consider the complexity of the project. Using the rafter style with sheds requires some woodworking know-how and precise cutting.
You need to determine what angles to cut the rafters, so they achieve the correct slant of your roofline while also providing a flush connection to your ridge board (this is called a ridge cut).
You also need to execute tricky cuts such as the colorfully-named birdsmouth cut. No, this cut doesn’t involve harming any of our feathered friends. A birdsmouth cut is a triangular-shaped notch taken out of each rafter that allows it to sit flush on the top plate of the exterior wall.
Getting this cut and your ridge cut executed properly, so both joints make a flush connection to both the ridge board and shed wall is crucial. You need to do this for every rafter board you use, making rafter construction time consuming and somewhat tedious.
Oh, and you need to do this outside, installing each rafter piece by piece. And make sure you don’t spend too much time measuring and cutting, because until you get that roof installed, it’s open season on your shed for Mother Nature.
In comparison, trusses are less complex. If you’re able to purchase a prefabricated truss, then the installation process is exponentially easier since someone else has done most of the work for you.
Even if you need to build each truss yourself, you have several things in your favor. First, you can build it in the comfort of your garage, aligning and assembling each piece on a flat smooth surface.
And once you’ve made one, you have a pattern to follow for each truss that comes after.
Time is also on your side. If you know before you begin construction on that shed that you’re going to use trusses, then you can build your trusses first, so they’re ready for installation when the time comes.
This limits the time your shed has to spend exposed to the elements.
One reason trusses are used so much more in the construction of houses is that they are significantly stronger and can, therefore, span greater distances without the need for load-bearing internal walls.
This strength advantage is due to all that webwork that adds support to each truss.
That said, this is only an advantage if you’re building a very large shed. Trusses can generally handle spans of up to 60 ft. while rafters can only handle about 30 ft. However, rafters can support a broader distance if a ridge beam is employed.
Before you decide that your 20 ft.-wide shed should do just fine with rafters, consider that those distances begin to shrink when you add weight, like say a couple of hundred pounds of snow and ice.
If you live in a part of the world that sees a significant amount of frozen precipitation each year, then you probably need that added strength to your roof to prevent it from sagging or even collapsing under the weight of all that white stuff.
There are significant cost differences when considering a truss style roof vs. a rafter style roof for a home. Because of the professional expertise and time required for rafter construction, roofs built using rafters can cost as much as 50% more than roofs built using trusses.
Unless you plan on hiring someone to help you build the roof, that’s generally not the case with sheds. Rafter style roofs may cost you a bit more due to waste from all the cutting you’ll need to do; however, that’s only if your other option was a prefabricated truss.
Building your truss will also result in considerable waste and, thus no cost savings.
Which Roofs Are Better Suited for Trusses…Rafters?
Although you can use a truss or rafter roof for most roof styles, there are certainly advantages and disadvantages depending on the style of roof you choose.
A gambrel style roof, for example, is better served by rafters. Why? This barn-style shed has a roof that accounts for a significant amount of your barn’s interior space.
Filling it up with truss webwork would make a shed with a gambrel roof virtually unusable unless it is very tall. Although some gambrel trusses are designed to create an attic space, this is a roof style that is much better served by rafters.
Similar to a gambrel style roof, if you’re going with gables, the space in the attic that is created by the shed’s steep roof pitch is valuable for storage. You don’t want to fill it with truss webbing. Rafters are the logical choice here.
That said, you can make a simple truss that will work for a gable and still give you storage space by eliminating some of the truss webs. Just remember that this will weaken your roof, so only use this option for smaller sheds.
For smaller roof profiles such as the saltbox, you have the option to go with either rafters or trusses. With the roof space being relatively smaller in this roof style, trusses require little webbing and only eliminate a small amount of space from the roof area.
If you live in an area that sees a significant amount of snowfall each year, consider using trusses or including ceiling joists as part of your rafter design for a saltbox shed.
You’ll rarely see trusses used with smaller sheds with these roofs styles. It’s unnecessary and the webbing will eat up valuable space on the shed’s taller side.
Unless you plan on using a ridge beam, wider sheds of this style need the added strength that trusses have to offer to prevent the roof from sagging. Remember, the greater the span of your roof, the stronger your roof design needs to be.
More complicated roof styles aren’t compatible with trusses. Because of their shape, hip, octagonal and pyramid shed roofs can only be built using rafters. Besides, part of the allure of these roof styles is their vaulted ceiling look, which only works if the roof space is left open.
Trusses and rafters both offer advantages in roof design. Trusses provide strength and ease of installation while rafters, though requiring more time and expertise to install, allow for more storage space in your shed’s attic and a wider variety of roof styles.
When it comes time to decide whether roof trusses or rafters are right for your shed, consider the strength and functionality you need from your shed’s roof as well as the roof style that best suits your property.