Impact of loose-laid gravel on the pressure distribution over a flat roof

A series of large-scale wind tunnel tests were conducted to quantify the impact of loose-laid gravel on the pressure distribution over a flat roof. Measurements are presented for the pressure distribution over the surface of a flat roof on a square-plan building for a broad range of parapet heights and wind angles. Data were collected for both smooth impermeable roofs and roofs covered with loose-laid permeable gravel. Mean and peak pressure contours are presented for nine different wind angles between 0 o and 45 o and seven parapet heights. The results for the smooth impermeable roof are consistent with prior studies which show that, for cornering winds, small parapets can lead to higher mean and peak suctions at certain locations on the roof surface. This is also true for the pressures at the top of a gravel roof surface. However, in general, it is shown that the pressure at the surface of a gravel roof is substantially lower than for a smooth impermeable roof surface located at the same height as the top of the gravel layer.