Engineered Trusses vs. Rafters When Installing Solar

One of the most important factors when installing roof-mounted solar panels is the condition and structure of the roof. It’s vital that a roof be able to not only hold up the weight of the solar panels, but also withstand any wind loads that could pull on the roofing. And when it comes to roof structure construction, there are two main methods: rafters (also know as stick built) and engineered trusses.

Both rafters and engineered trusses can provide adequate structure for solar panel installation. However, each has its pros and cons. And depending on where you live, local structural requirements might favor one over the other.

Let’s take a look at the differences between rafters and engineered trusses, their pros and cons, and what to consider when installing solar panels on both types.


Rafters have been used for centuries for roof support. That’s because rafters are a fairly simple but effective way to support a roof. Until recently, rafters were used in a majority of newly constructed homes.

Rafters are long wooden boards used for the frame of the roof, also known as stick framing. Typically, rafters are made on the job site by the roofers and are often cut into 2×10 or 2×12 beams. Normally, just two of these beams slope down from the peak or hip of the roof and meet the walls. Ceiling joists then help secure the rafters and the exterior walls, and a ridge beam or ridge board is placed at the center of the roof, which helps to support the roof rafters at the top.

Rafters provide a simple solution to roofing structural needs. They also allow for greater attic space and easier insulation installation because of their simple and open design. Plus, because rafters are built on the jobsite, they are easier to customize to fit changing construction situations and require less planning than trusses.

However, rafters do have their drawbacks. Rafters require professionals with the proper skills and experience. And because rafters are being used less and less in building projects, it is getting more difficult and more expensive to hire those professionals. On top of that, building rafters on site can take a lot more time than trusses, which are prebuilt in a factory and delivered to the site when needed.

To identify if your house has rafters, one of the best ways is to look in the attic. If your attic space is relatively open with few or no crossbeams and has parallel boards running from the peak to the walls, you likely have rafters. See the images above for examples of roofs constructed with rafters.



More Attic Space: Because rafters don’t have webbing or struts (which trusses do), there is more space underneath the roof. This extra space can be used for additional rooms or storage space and is ideal of you plan on converting the attic space in the future.

Easier Insulation Installation: Installing insulation in a roof with rafters is easier than one with trusses. Roofs with rafters have more space to move around, and the insulation can more easily be installed between the rafters.

Lead Time: Because rafters are made on the building site, they require less planning and work than trusses.

Easier to Customize: Rafters can be more easily customized than trusses. That’s because rafters are built on site and can be tailored to the construction needs if situations change. Trusses are prebuilt in a factory and cannot be altered on site without undermining structural integrity.



Higher Cost: Although rafters can take less time to build and install, the wood and labor cost more than for trusses. Rafters require professionals on site with the proper knowledge, and more wood is required for rafters than for trusses.

Longer Construction: Because rafters are built on site, there is a lot more time required to build the roof. Depending on the job, it could take a week or more to construct a roof with rafters. This is opposite of trusses, which are built in a factory to the required specs and then delivered to the site when needed.

Requires Professionals: Rafters are built on site, which means a professional with the proper experience and knowledge is required. However, these professionals and this knowledge are becoming more challenging to find as more and more buildings are using trusses instead of rafters.


Several decades ago, a majority of roofs were constructed with rafters. However, as materials and design technology have advanced, engineered trusses have become to go-to standard for homebuilders.

Engineered trusses, or trusses for short, are made of prefabricated lightweight wood that is constructed in a factory, typically from larger pieces of wood like 2x8s or 2x10s, and delivered to the home construction site. Unlike rafters, trusses feature beams on the top and bottom and an arrangement of webbing that allows them to distribute the load more broadly to the outside walls.

There are many different types of roof trusses where the webbing posts are arranged in different patterns, providing different uses. The most basic roof truss is the King Post truss, which requires fewer materials, and costs less than the others.

One of the positive features of trusses is their strength. Because trusses have webbing that runs between the beams, the weight of the roof can be evenly distributed and greatly improve the roof’s structural integrity when compared to roofs made with rafters.

Another huge benefit of trusses is that they are built in a factory. This allows the trusses to be built exactly to specifications in a controlled and consistent environment. And when those trusses are completed, they are delivered to the building site. This cuts down on the time and space needed on the jobsite, which means less money and faster construction.

However, there are downsides to using trusses. One of the downsides of trusses is the space they take up in an attic. Because of the webbing in trusses, there is less attic space and it is very difficult if not impossible to make future modifications to the space, such as adding rooms.

Another potential downside of trusses is difficulty in customization. While it can be easy to plan out exactly what you need ahead of time for trusses and have them built in a factory, this can lead to headaches later. If modifications need to be made last-minute on the jobsite, it can be very difficult if not impossible to do so. Trusses are custom engineered and built, and almost any modification will negatively impact their structural integrity.

To identify if your house has trusses, check your attic space. If your house has trusses, it’s likely there are beams spanning between the roof and a lower beam, breaking up the attic space. Those are the truss webbings and likely means your roof was constructed with engineered trusses. See the images above for examples of roofs constructed with trusses.



Higher Quality: Because trusses are built in a controlled environment with precision equipment, their quality is often much higher and leads to a tighter roof design.

Delivery: Once trusses are completed in the factory, they are then delivered to the jobsite. This is much more convenient and saves time, space, and money compared to rafters.

Faster: Trusses can be installed much quicker than rafters because they are prebuilt and delivered ready for construction. Constructing a roof with trusses can be done in a matter of days instead of weeks.

Stronger: Trusses are built with webbing that distributes loads more broadly and increases their structural integrity.



Less Attic Space: Because of the webbings in trusses, there is much less attic space available. This means there is less space to move around for work in the attic, such as insulation installation, and very little chance of any future modifications or room additions in that space.

Harder to Customize: Once a truss is fabricated in the factory, it is nearly impossible to alter it without undermining the structural integrity. This can be a problem if unplanned modifications are needed accommodate the roof construction.


Rafters and trusses are both great forms of roof support. After centuries of trial, error, research, and development, they have enabled the construction of buildings that are stronger than ever. And because of this, both are quite capable of supporting solar panels.

As we discuss in another article, modern roofs are very sturdy and can hold up a lot of weight. A typical roof can support 20 pounds per square foot or more, while solar panels only add approximately 2.3 pounds per square feet. So don’t worry, solar panels alone won’t cause your roof to collapse.

However, there are certain factors to consider when determining if a roof is a good fit for solar panels.



The condition of the rafters and trusses are of vital importance when considering to install solar panels. These are the major supports that will be holding up the solar panels and be used to secure the solar racking, so they should be in good condition.

Rafters and trusses should be inspected carefully by a professional to ensure they are in good shape. Things to watch out for include signs of moisture, such as mold or fungus growth, discoloration, or rot. It’s also important to notice any cracks, which could be a sign of structural stress. And if any modifications have been done to the rafters or trusses, they should be inspected extra carefully to ensure those modifications did not undermine structural integrity.




Also of vital importance for a solar install are the age and condition of the roof. A proper inspection of the roof’s condition should be done before solar panels are installed. If the roof is structurally unsound, it should be repaired or replaced before installing solar panels.

The same is true of the roofing material. For instance, if the shingles are deteriorating or metal is rusting, it is a good idea to consider replacing the roof before installing solar panels. This is also the case if a roof is nearing the end of its expected lifespan. Solar panels have a lifespan of 30 years or more. If the roofing material is expected to need replacing within that timespan, it could be a good idea to replace the roofing material beforehand. Otherwise, the solar panels will need to be removed, the roofing material replaced, and solar panels reinstalled.



Another factor when determining if you can install solar panels on rafters or trusses is local solar policies and building codes. Some local governments have policies and codes in place that require certain roofing structures when installing solar panels. Other local governments will require special inspections, engineering, and reporting before solar panels can be installed on certain roofing structures.

For instance, in Multnomah County in Oregon, solar panels can be installed on either rafters or trusses. However, there are special reporting and engineering requirements for houses with rafters.

As Tyler Cox, senior project manager at Green Ridge Solar, explains, “A home with rafter may or may not be ok, it all depends on the size and spacing of the rafters, the ceiling and floor joists, and the interior layout of the house and how the roof loads are carried down to the foundation. Those are all things that we need to get measurements of, and then have to translate via photos and drawings to an engineer, who then has to make everything calculate out ‘just so’ for the building department to accept it.”

As you can imagine, this adds a significant amount of time, cost, and potential frustration to a solar installation.

“That’s how we end up with customers that take 6 or 8 or 12 months to get through permitting, and need thousands of dollars of engineering and structural upgrades (not to mention the multiple site visit and hours of my screen time) to get done,” Cox said.

So while solar panels can be installed on both rafters and trusses, these local policies and building codes can make building on certain roof structures very time and resource prohibitive. This is an important consideration when deciding if your roof is a good fit for solar panels.


Whether your roof is constructed with rafters or engineered trusses, both can be good fits for solar panels. Both rafters and trusses provide significant structural integrity for a solar panel installation, and most solar companies have significant experience installing on both types of roof supports.

To determine if your roof is a good fit for solar panels, it’s best to contact your local solar company. Local solar companies have knowledge and experience with the types of roofing material and structures used in your area. They also have knowledge and experience with the various solar policies and building codes that need to be complied with.

Green Ridge Solar is Oregon’s local solar company, and we have significant experience installing on all types of roofs. Plus, we also have strong knowledge and experience working with local governments and utilities, so we know the ins and outs of local solar policies and building codes.

Contact Green Ridge Solar today to see if your roof is a good fit for solar. You can also receive a free solar analysis, along with a thorough outline of all the solar incentives you qualify for.


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