Dead Load. The additional dead load of 10 to 25 psf
for gravel ballast or pavers is readily accommodated in new
construction. But reroofing of existing buildings obviously
requires a check of the original structural design to determine
if the structural framing has excess capacity over its original
design load. Inspection of the roof's structural components to
assure its sound condition is also recommended. Additional
ballast load required at the roof perimeter may sometimes be
averted by a combination anchored/ballasted system, described in
Factory Mutual Data Sheet 1-29 Technical Advisory Bulletin,
Loose-laid Ballasted Roof Coverings.
Mechanical Fasteners. For manufacturers' approved
mechanical fasteners and fastener patterns, refer to the latest
edition of the Factory Mutual Approval Guide.
Design Data. For design guidance on wind-uplift
pressures for various U.S. locations, wind-design procedures, and
other details, consult Factory Mutual Publications. For design
guidance for locations outside the U.S., refer to
MIL-HDBK-1002/2, Structural Engineering - Loads.