Flat roofs need drains at each low point (or overflow drains); sloped roofs drain over edges via gutters or scuppers

Description

Unless roofs are sloped to drain over roof edges, roof drains must be installed at each low point of the roof. Where roof drains are required, an overflow drain or scupper must also be provided to drain runoff if the primary drain becomes blocked. Slope minimums for flat-roof drainage are typically ¼ in per ft (2%) to the drain.

Why this exists

Roof drain failures cause cascading water damage. The overflow-drain rule is the architect's insurance policy — if the primary drain clogs in a leaf storm, the overflow takes over. Specify both at every low point with separate, independent paths to grade.

Categories

Applies to

• Jurisdiction: New York State

Source

Solver enforcement

Browsable only — the solver does not currently enforce this directive (no spec-level data to check against). This entry exists so the architect personas can cite it in conversation and the user can read what the rule says.

Related directives

• Habitable space minimum ceiling height · IRC R305.1
• Wind design · IRC R301.2.1
• Seismic provisions · IRC R301.2.2
• Snow loads · IRC R301.2.3
• Floodplain construction · IRC R301.2.4