Air-Permeability Factor for Wind Loads on Loose-Laid Pavers on Flat Roofs

Abstract

Installation of open-joint roof paver systems with pedestals on flat roofs leaves a cavity between pavers and roof deck, allowing the development of cavity pressure. The cavity suction on roof pavers reduces the net wind uplift and overturning. This study conducted pressure measurements of the paved roof of a large-scale building model using the University of Western Ontario’s WindEEE Dome. The air-permeability factor was evaluated as a ratio of directional envelopes of peak net-pressure coefficients of the paved roof to peak external pressure coefficients of the bare roof. The air-permeability factors varied with pavers’ location across the roof, and wind uplift load decreased 40% for pavers in the corner and edge roof zones. Moreover, pressure tests conducted on roofs with high perimeter parapets showed that air-permeability effects of pavers and shielding effects of perimeter parapets can be treated as independent aerodynamic factors for evaluating the net uplift wind loads on rooftop pavers. Therefore the overall effect can be obtained simply by multiplying the roof pressure on bare flat roofs by air-permeability and parapet factors.