Ballasted Mount System

A ballasted mount system is a type of solar racking that uses heavy weights (ballast) — typically concrete blocks — to hold panels in place on a flat or low-slope roof without penetrating the roof membrane. This approach avoids drilling holes in the roof, preserving the roof warranty.

Ballasted systems are most commonly used on commercial flat roofs but are also suitable for residential flat roofs and some low-slope roofs. The panels sit in trays or frames angled at 5°–15° and are held down by the weight of the ballast blocks. A structural engineer must verify that the roof can support the additional weight of the panels, racking, and ballast (typically 3–6 pounds per square foot). The main advantage is zero roof penetrations, which eliminates leak risk and simplifies installation. The downsides are the added weight and the inability to tilt panels at steeper angles that might optimize production. Wind uplift calculations are critical — in high-wind areas, more ballast weight or supplemental mechanical attachments may be required. Ballasted systems are generally easier to remove and relocate than penetrating roof mounts.