Exterior Wall Opening Limit by Fire Separation Distance (IBC Table 705.8)

Capped as a percentage of the wall area by the fire separation distance and by whether the openings are protected or the building sprinklered. A wall under 3 ft from the line gets none; at 5 to 10 ft a sprinklered wall may be 25% glass; at 30 ft or more there is no limit. The distance to the lot line, not the facade design, sets the glass - one of the strongest arguments for a sprinkler system on a wall tight to the property line. A design aid, not a code-official determination.

band = f(fsd_ft, protected) from Table 705.8; allowable_pct = band; allowable_area = band x wall_area (Infinity = no limit); pass = actual_opening <= allowable_area.

IBC 2021 Table 705.8 (maximum area of exterior wall openings) and §705.3 (measurement of the fire separation distance), by name.

The opening-area limits are stated in the published IBC Table 705.8; the percentage comparison is public arithmetic.

Estimate. AHJ and licensed professional govern.

Field names used by the API: fsd_ft, wall_area, protected, actual_opening, allowable_pct, allowable_area, pass

• Band lookup the allowable percentage is set by the fire separation distance band and by protection / sprinkler statusIBC 2021 Table 705.8
• Sprinklered equals protected unprotected openings in a sprinklered building take the protected allowance per Note aIBC 2021 Table 705.8 Note a
• Measurement the fire separation distance is measured per §705.3 to the lot line, public-way centerline, or an assumed line between buildingsIBC 2021 §705.3