Fire Separation Distance Calculator

Calculate exterior wall fire resistance ratings and allowable opening percentages based on fire separation distance per IBC Chapter 7.

Distance from exterior wall to property line or centerline of public way
Total area of exterior wall facing property line
Proposed unprotected opening area as % of wall

IBC Table 705.8 - Allowable Openings

FSD (ft) Unprotected Protected
0-3Not PermittedNot Permitted
3-515% (Sprk: 25%)15%
5-1025% (Sprk: 45%)45%
10-1545% (Sprk: 75%)75%
15-2070% (Sprk: Unlim)No Limit
20-30UnlimitedNo Limit

Sprk = NFPA 13 sprinklered throughout. FSD = Fire Separation Distance

Fire Separation Distance Concepts

Measurement

FSD is measured perpendicular from the exterior wall face to the closest property line or centerline of a public way (street/alley).

Assumed Imaginary Line

For buildings on same lot, an imaginary line equidistant between buildings may be used for FSD calculation.

Sprinkler Benefits

NFPA 13 sprinklered buildings typically allow increased opening percentages per IBC 705.8.1.