If you’re considering installing solar panels on the roof of your home or business, one of the first things you need to do is ensure your roof can support the added weight. The roof of a modern building is often sufficiently strong to carry the weight of a solar panel installation.
Nonetheless, you don’t want to take any risks since there’s always a chance that the panels could cause the roof to collapse. Learn more about all you need to know about roof loads, load capacities and how they determine if a roof can support the weight of solar panels.
Understanding Roof Loads and Load Capacity
Roof load capacity is simply a measurement of how much total weight a roof can support per square foot. When calculating the necessary load capacity of a roof, you need to figure in what’s known as the dead load along with live loads or environmental loads.
The dead load is the total weight of the roofing materials (shingles, tiles, etc.) as well as the weight of any other permanent objects, such as a roof-mounted HVAC unit or solar panels. Live loads and environmental loads refer to the additional temporary weight of something like a person walking on the roof or snow and ice on the roof.
Building codes generally require that a roof has a minimum live load capacity of 20 pounds per square foot. This is in addition to the capacity required to support the dead load. However, the live load capacity requirements are sometimes higher in places that experience heavy snowfall to ensure that the roof can support several feet of snow without collapsing.
Older homes sometimes have a lower capacity than what the current code requires. Nonetheless, this is fairly rare since you’re usually required to bring the roof up to the current code requirements when replacing it. That means you mostly only see a roof with a lower load capacity on an old home that still has the original roof or in places that don’t require building inspections.
How Much Do Solar Panels Add to a Roof’s Load
In the past, solar panels were quite bulky and fairly heavy. That means it was often necessary to install additional trusses or rafters and extra bracing to ensure the roof could support the weight of the solar panels. New solar panels by brands like Tesla are fairly thin and lightweight. In most cases, a solar panel installation will now only increase the load on a roof by somewhere around 2 to 4 pounds per square foot. The number of solar panels you install generally makes no difference as all that matters is the additional weight per square foot.
How much weight solar panels add per square foot can vary depending on the type of mounting brackets and racks used and how many total mounting locations there are. When mounting the solar panels, some installers will try to use as few mounting brackets as they can. This is because the more brackets they need to connect to the roof, the more places there are that could potentially start leaking.
The issue with using fewer mounting locations is that it can result in the weight of the panels not being distributed evenly. That means the point load or the weight on the parts of the roof directly underneath the brackets ends up being much greater.
That’s why you want to make sure you hire an experienced company to install your solar panels so you can ensure the weight is more evenly distributed. They will also use metal flashing and sealant around the mounting brackets when installing everything to help ensure that the roof doesn’t end up leaking.
How to Know If Your Roof Can Support the Weight of Solar Panels
Even though new solar panels typically don’t substantially increase the load on a roof, you may still need to have additional support added before installing them. The reason is again due to the difference between dead load and live load. The solar panel installation will increase the dead load on the roof, which results in a decrease in its live load capacity.
That’s why you need to have a professional residential roofing company inspect your roof and calculate its current dead load, what the dead load will be after the solar panels are installed, and what its current live load capacity is. If the solar panels will decrease the live load capacity to under 20 pounds per square foot, you’ll need to add extra support before installing the panels.
The main factors that typically determine whether a roof is strong enough to support a solar panel installation are the age of the roof and the type of roofing materials. In terms of age, the most important things are the condition of the underlying wooden roof sheets and the wooden rafters or trusses.
If there are damaged shingles or tiles or the roofing membrane is damaged, there’s a good chance that some of the sheets have started to rot. Leaks can also result in the rafters or trusses rotting, cracking, or warping and the roof not being able to support nearly as much weight. These issues are one reason why you may want or may have to replace your roof before installing solar panels.
You’ll usually be fine if your roof was replaced fairly recently. Otherwise, replacing it at the same time you have the solar panels installed is a smart decision. Part of the reason is that it will save you the additional cost and hassle of needing to have the solar panel installation removed if your roof ends up needing to be replaced in the next few years. If you install a new roof and the solar panels at the same time, this likely won’t be an issue since the panels will typically have around the same life expectancy as the roof itself.
Whether you have a shingle or tile roof can sometimes play a role as well in whether the roof is strong enough to support solar panels. Concrete, slate, and clay tiles are extremely heavy compared to asphalt and composite shingles.
That means a tile roof will usually already have lots of additional supports so that it can carry the additional dead load of the tiles. If you have an asphalt roof, there is a higher chance you’ll need to reinforce it before installing solar panels unless its live load capacity is well above the minimum requirement.
For the past 20 years, the team at KPost Company has been putting their experience toward helping homeowners and business owners in the Dallas area with all of their roofing and solar power needs. We install traditional solar panels as well as Tesla solar roofs and will work to ensure your solar installation is safe and meets your specific needs.
We also install Tesla Powerwall battery backups so you can store the excess power from your solar panels and ensure you get the most out of your solar installation. If you’re concerned about the condition of your roof, you can count on us to perform a full inspection and determine if you need any roof repairs or if you should replace your roof before installing solar panels. We work on almost all types of roofs and a wide range of roofing materials and will make certain all of your needs are expertly met.
To schedule a solar installation consultation or any roofing service, give our team at KPost Company a call today.
