Wind Resistance of Ballasted Concrete Blocks in Rooftop Solar PV

On concrete flat roofs, distributed rooftop solar arrays often use precast concrete ballast blocks instead of roof penetrations. These blocks resist wind through gravity: their dead weight creates a restoring moment against uplift and sliding forces acting on the modules and rails.

Wind performance is not a fixed property of the block alone. It depends on block weight (typically 20–50 kg, C25–C35 concrete), array tilt (usually 5°–15°), perimeter ballast zoning, and aerodynamic add-ons such as wind deflectors. Engineering practice sizes each block to at least 1.5–2.0 times the combined wind-uplift load based on local 50-year return wind pressure; edge and corner rows receive 1.5–2.0× the interior ballast.

A standard square block handles 8–10 level winds, while optimized round blocks or deflector-equipped systems reach 40–60 m/s design wind speed. During layout and setting-out, crews must keep clear of parapets, place EPDM pads under blocks, and verify roof dead-load capacity before deployment.