Ballasted Roof Ballast Weight and Order

Total dead load = roof area x ballast rate: 5,000 sf at 12 psf = 60,000 lb (30 tons). Stone is ordered by the yard, so volume = weight / bulk density (~90-105 pcf river gravel) / 27 = 22.2 cu yd, ~1.4 in deep. The BALLAST RATE is set by ANSI/SPRI RP-4 from the building height, roof-edge/parapet condition, and wind zone: often 10 psf (nominal 1,000 lb/square) of smooth #4 river gravel in the field, rising to ~13-15 psf or concrete pavers at the corners and perimeter and on taller/higher-wind buildings. A dead-load and ordering SCREEN, not a wind-uplift design; RP-4 and the structural engineer set the rate and zone layout, and the deck capacity governs.

total_ballast_lb = roof_area_sqft x ballast_psf; total_tons = total_ballast_lb / 2000; stone_depth_in = ballast_psf / stone_density_pcf x 12; volume_cy = total_ballast_lb / stone_density_pcf / 27.

Ballasted single-ply roof ballast weight and order quantity (ANSI/SPRI RP-4 ballast rates), by name; RP-4 and the structural engineer set the ballast rate and zone layout, and the deck capacity governs.

The takeoff is public first-principles (weight = area x rate, volume = weight / bulk density); the ballast rate comes from ANSI/SPRI RP-4 and the stone bulk density from the supplier.

Estimate. AHJ and licensed professional govern.

Field names used by the API: roof_area_sqft, ballast_psf, stone_density_pcf, total_ballast_lb, total_tons, volume_cy, stone_depth_in

• Weight and order volume total lb = area x rate; tons = lb/2000; order cy = lb / bulk density / 27; stone depth = rate / density x 12material-takeoff practice
• Ballast rate per RP-4 ANSI/SPRI RP-4 sets the rate by building height, edge condition, and wind zone (~10 psf field minimum, higher/pavers at corners and perimeter); a dead-load screen, not an uplift designANSI/SPRI RP-4