Compliance News: Noncombustible Sills for Fire Doors

By Robert Trotter, CBO, CFM

Fire rated doors must be installed properly so that fire cannot spread below, around, or above the door. To minimize the risk for fire spread at the undercut of a fire door, NFPA 80, Standard for Fire Doors and Fire Windows, 1999 edition describes the requirements for sills. Section 1- 1.2.1 states, “In buildings with noncombustible floors, special sill construction shall not be required, provided the floor structure is extended through the door opening.” Largely, healthcare occupancies have noncombustible floor construction and no special sill construction would be required. This means the example pictured would be compliant even though the carpet extends through the door opening. However, Section 1-11.2.3 states, “Combustible floor coverings shall not extend through openings protected by 3-hour rated fire protection door assemblies.”

In buildings with combustible floors or combustible floor coverings, special sill construction is required if the floor structure is extended through the door opening, as combustible floor construction is not permitted to extend through the door opening except door openings required to be protected by 20- or 30-minute doors. All sills must be constructed of noncombustible materials. Consult NFPA 80 for additional details regarding the arrangement of sills.