What should I evaluate on my building's roof before going solar?
A thorough roof assessment determines feasibility, cost, and optimal system design for your solar installation.
Evaluating your building's roof is critical for determining solar viability, project cost, and system design. Here's what to assess:
Roof Type and Condition
The roof's material, shape, age, and condition all affect installation requirements. Commercial roofs typically consist of metal, built-up roofing (BUR) membrane, modified bitumen (asphalt and rubber), or single-ply materials like TPO, PVC, or EPDM.
A roof's age and condition matter significantly. A 25-year-old roof in poor condition may need replacement before solar installation. However, timing can work in your favor: solar systems last 25–30 years, and new roofs last 20–40 years depending on material, making concurrent replacement and installation cost-effective. Roof type, age, and condition can typically be found in construction drawings or warranty documents.
Roof Slope and Pitch
Roof slope measures the incline expressed as a ratio, degrees, or percentage. Flat roofs are less than 12.5 degrees, low-slope up to 30 degrees, and steep-slope greater than 30 degrees. Slope determines your racking system type — flat or low-slope roofs can use ballasted (weighted) racking with no roof penetrations, while steep-slope roofs require anchored systems.
Roof Warranty
Most warranties include a manufacturer's warranty covering material defects, a workmanship warranty covering installation quality, or a full-coverage warranty combining both. When solar is installed, the solar provider coordinates with the warranty issuer to ensure the warranty remains valid.
Available Installation Space
Usable roof area is limited by obstructions like HVAC equipment, vents, skylights, wires, and water tanks. Fire setbacks — mandatory distances from roof edges for firefighter access — typically range from 1.5 to 3 feet. Taking photos and videos of the entire roof helps solar providers accurately assess available space.
Live and Dead Load Capacity
Solar installation adds weight to your roof. Live load is temporary (snow, wind, people), while dead load is permanent (roof structure and equipment). Load limits in pounds per square foot are found in construction drawings or roof warranties. If unknown, a structural engineer must perform an assessment before installation can proceed.
Providing complete documentation — construction drawings, roof warranties, maintenance records, and clear photos — ensures accurate feasibility studies and realistic cost estimates.