Code guides · ASCE 7
Roof wind zones (field / perimeter / corner)
ASCE 7's roof zoning drives fastener density on every TPO / EPDM / mod-bit job. The corners and perimeter need 2-3× the field's fastener count.
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Zone definitions (low-rise, condensed)
- Zone 1 (field): interior of the roof; lowest pressure
- Zone 2 (perimeter): edges, typically 2× zone 1 pressure
- Zone 3 (corner): roof corners, typically 3× zone 1 pressure
- Width of perimeter / corner zone scales with building height + width
Takeoff impact
OmniTakeoff differentiates the zones automatically from the roof outline. Field SF + perimeter LF + corner SF roll up as separate takeoff line items so the fastener pattern + manufacturer-required spacing apply correctly.
Disclosure
This is a plain-English summary for estimating purposes. It is not a substitute for the actual code documents — review for AHJ-specific amendments. Adopted editions vary by jurisdiction; OmniTakeoff applies the edition declared on the project, not a hard-coded default.
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