If you live in California, you may have heard the news by now - starting January 2020, solar power generation systems will become mandatory for all new residential buildings less than 3 stories high. If your project falls under this new regulation, you may have already started to contemplate the effects on your bottom line. While the costs are a natural thing to worry about, have you stopped to consider how a solar array can impact your building’s design? For instance, can a rooftop solar system exceed the maximum allowable building height?
Height restrictions exist for a variety of reasons. In the California Building Standards Code (CBC), their primary justification is fire safety. Taller buildings built with combustible construction materials give emergency crews less time to respond and evacuate the occupants due to the poor fire resistance of materials and the quick rate of flame spread.
The CBC establishes maximum building heights based on occupancy, type of construction, as well as the type of sprinkler system. Non-residential buildings of fire-resistive and non-combustible construction typically have a higher threshold, with some building types having no height restrictions at all.
On the other hand, residential occupancies, particularly wood-frame dwellings have lower height limits. For example, the allowable height of a wood frame single-family home ranges from 40 to 60 feet, depending on the type of sprinkler system used. To facilitate the installation of photovoltaic systems, the Building Code grants certain exceptions to its maximum height regulations. Rooftop solar panels affixed to a structure with nothing underneath are not considered an additional story, or extra floor area, and may exceed the height limits as long as the conditions below are met:
1. In all occupancies, the highest point of the structure or panel may extend up to 3 feet above the allowable building height, or 3 feet above the roof of the building directly below, whichever is lower.
2. When installed on flat roofs of buildings of any occupancy other than R-3 and R-4, the highest point of the structure or panel may extend up to 10 feet above the allowable building height, or 10 feet above the roof of the building directly below, whichever is lower.
Note that per the CBC, a building’s height is the vertical distance between the average point of grade adjoining the exterior walls and the average height of the highest roof surface.
Local zoning codes also stipulate building height limits in their design guidelines. There is an array of reasons a zoning ordinance may impose height restrictions for certain occupancies and/or neighborhoods of the jurisdiction: preservation of neighborhood character, maintaining views of important buildings, and air navigation safety, just to name a few.
Often, building heights correlate to setback distances, with longer setbacks allowing you to build higher. Homes with pitched roofs typically have higher limits than those with flat roofs.
There are many other variables, and the requirements fluctuate between jurisdictions. For example, in San Francisco, the height limit in most residential areas ranges between 35-40 feet. In Los Angeles, the height of a single-family dwelling is mostly limited to 28 feet if the roof has a pitch of less than 25% and 33 feet for homes with steeper roofs. Solar structures in Los Angeles may project up to 3 feet above the surface of the roof, even if the roof is at or above the height limit. System height exceptions vary between cities and counties, so take the time to do your research before you install your solar system.
Building and zoning codes may establish height limits, but there are some other factors to consider as well when determining the solar system height and location. Environmental factors such as wind and heat, as well as the location of roof vents and HVAC units, must all be taken into account. If the solar array is installed too close to the surface of the roof, the panels may overheat and lose their conversion capacity. On the other hand, too much clearance may lead to increased exposure to wind forces and result in damage to the solar panels and adjacent properties. Roof vents and HVAC units require ample clearance to function properly, and the layout of the solar panels must be designed with this in mind.
Can your roof support the added weight of the solar panels? Before you commit to purchasing the system, get a structural engineer to evaluate your home’s roof structure, and see if additional reinforcement is needed.
Will your roof need repairs or replacements after the solar panels have been installed? The condition of the roof covering is another factor to consider. Most PV systems have a lifespan of 25 to 30 years, and if you doubt that your roof covering will last that long, you should replace it before you install the solar panels.
Whether you’re installing solar panels on a new or an existing building, there are many variables to figure out to make your project a success. Our engineers can help. We will confirm the local and state height restrictions, verify the roof’s ability to support the solar panels, get your project permitted and make sure that installation goes off without a hitch. Let our team of experts put your mind at ease. Contact us at (877) 704-5727 or email us at email@example.com to discuss your project and get a free quote today.