Ballasted roofing systems use the weight of aggregate or concrete pavers to retain the roof build-up without penetrations. When solar PV is installed on a ballasted roof using a non-penetrating mounting frame, the structural engineer must account for the combined weight of the existing ballast and the PV system ballast, which can result in very high total dead loads.
Existing ballast loads on inverted warm-deck roofs typically range from 50 to 80 kg/m². Adding a ballasted solar mounting system at 20 to 30 kg/m² results in total dead loads that older roof structures may not have been designed to carry. A Desktop Structural Roof Loading Report can assess whether the structure can accommodate the combined loading within the 48-hour delivery benchmark where drawings are available.