LGreene
Registered User
In buildings with combustible floors or combustible floor coverings, NFPA 80 requires a noncombustible sill for fire doors rated 45 minutes or more. The NFPA Glossary of Terms defines a sill as "The bottom part of an opening over which a fire door closes,” (not very specific), but there's a drawing in the Annex of NFPA 80 that shows a raised metallic threshold as one option for combustible floors. Although the threshold is drawn on top of a "fire wall (brick, masonry, concrete)".
View attachment 1999
My questions: Is a sill a threshold, or part of the floor construction? Are buildings allowed to have combustible floors these days? If we're working on an old building, is it likely to have a combustible floor? When (if ever) is an aluminum threshold required for a fire door? Here's the section from NFPA 80:4.8.2 Sills.4.8.2.1 In buildings with noncombustible floors, special sillconstruction shall not be required, provided the floor structureis extended through the door opening.4.8.2.2 In buildings with combustible floors or combustiblefloor coverings, special sill construction shall be required ifthe floor structure is extended through the door opening, ascombustible floor construction shall not be permitted to extendthrough the door opening.4.8.2.3 Door openings required to be protected by 1⁄2-hour or1⁄3-hour rated fire protection door assemblies shall be exemptedfrom the requirements of 4.8.2.2.4.8.2.4 Sills shall be constructed of noncombustible materials.4.8.2.5* For swinging doors with builders hardware andspecial-purpose horizontally sliding accordion or foldingdoors with frames having a jamb depth of 4 in. (102 mm) orless, the sill width shall be equal to the jamb depth.4.8.2.6* Where frames have a greater jamb depth, the sillsshall have a minimum width of 4 in. (102 mm) and shall beinstalled so that the sill extends from the face of the frame onthe door side into the frame.4.8.2.7 For swinging doors with fire door hardware, sills shallextend at least the depth of the door frame for flush-mounteddoors.4.8.2.8* For lap-mounted doors, sills shall extend beyond theopening for a length equal to the projection of the installeddoor or doors.4.8.2.9* For horizontally sliding fire doors and vertically slidingfire doors, sills shall be constructed of noncombustiblematerial and shall extend 6 in. (152 mm) past the edge of theopening on each side and 4 in. (102 mm) out from the face ofthe wall.View attachment 1999
/monthly_2013_10/Sill.jpg.464bb4e29c05641dca33d10bab183bb5.jpg
View attachment 1999
My questions: Is a sill a threshold, or part of the floor construction? Are buildings allowed to have combustible floors these days? If we're working on an old building, is it likely to have a combustible floor? When (if ever) is an aluminum threshold required for a fire door? Here's the section from NFPA 80:4.8.2 Sills.4.8.2.1 In buildings with noncombustible floors, special sillconstruction shall not be required, provided the floor structureis extended through the door opening.4.8.2.2 In buildings with combustible floors or combustiblefloor coverings, special sill construction shall be required ifthe floor structure is extended through the door opening, ascombustible floor construction shall not be permitted to extendthrough the door opening.4.8.2.3 Door openings required to be protected by 1⁄2-hour or1⁄3-hour rated fire protection door assemblies shall be exemptedfrom the requirements of 4.8.2.2.4.8.2.4 Sills shall be constructed of noncombustible materials.4.8.2.5* For swinging doors with builders hardware andspecial-purpose horizontally sliding accordion or foldingdoors with frames having a jamb depth of 4 in. (102 mm) orless, the sill width shall be equal to the jamb depth.4.8.2.6* Where frames have a greater jamb depth, the sillsshall have a minimum width of 4 in. (102 mm) and shall beinstalled so that the sill extends from the face of the frame onthe door side into the frame.4.8.2.7 For swinging doors with fire door hardware, sills shallextend at least the depth of the door frame for flush-mounteddoors.4.8.2.8* For lap-mounted doors, sills shall extend beyond theopening for a length equal to the projection of the installeddoor or doors.4.8.2.9* For horizontally sliding fire doors and vertically slidingfire doors, sills shall be constructed of noncombustiblematerial and shall extend 6 in. (152 mm) past the edge of theopening on each side and 4 in. (102 mm) out from the face ofthe wall.View attachment 1999
/monthly_2013_10/Sill.jpg.464bb4e29c05641dca33d10bab183bb5.jpg
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