Glossary / soffit
Fire-resistant soffits and soffit vents
The finished underside of an eave or other overhang. OSFM 8160 lists underside coverings. Perforated soffit is not an ember-resistant vent.
A soffit is the finished underside of an eave or other horizontal projection, the board or panel you see looking up at the roof edge. In wildfire construction two different rules meet there: the covering of the underside, and any vent opening in it.
The underside covering. California's OSFM handbook category 8160 lists horizontal-projection underside products by model, most tested to SFM 12-7A-3, a direct-flame test of eave soffits and floor-projection undersides, some listed as noncombustible under-eave material (CWUIC row). Where Oregon R327 is adopted, the underside follows other named paths, including ASTM E2957. Un-vented HardieSoffit and CemSoffit on this site are 8160 under-eave records.
The vent opening. A perforated fiber-cement soffit is cladding, not an ember-resistant vent: it is neither 1/16 to 1/8 inch mesh nor an ASTM E2886 listed assembly. Where Oregon R327 is adopted, eave, soffit and cornice vents are restricted; the exceptions are a manufactured ember- and flame-resistant vent or an opening 12 feet or more above grade (the twelve-foot rule). Colorado's 2025 CWRC Class 2 asks for a noncombustible eave (row). IBHS Wildfire Prepared Enhanced adds enclosed eaves to the Essential ember package.
Category 8160 is the covering; category 8165 is the opening. A product listed in one is not listed in the other. The vents hub holds the listed vent models.
Questions
Are soffit vents fire rated?
Vents are listed to ASTM E2886 or meshed at 1/16 to 1/8 inch; fire rated is not the vocabulary. Where Oregon R327 applies, a soffit vent must be a manufactured ember- and flame-resistant vent or sit 12 feet or more above grade.
Do soffits need to be fire rated?
In California mapped areas the underside follows CWUIC, with SFM 12-7A-3 performance as one path and OSFM 8160 as the listing category; Oregon R327 names other underside paths. IBHS Enhanced asks for enclosed eaves.
Is soffit fire-resistant?
Only as the listed product: fiber-cement soffit panels appear in OSFM 8160 as noncombustible or 12-7A-3-tested under-eave material by model. A perforated panel is still cladding, not a vent.
Do not use as a synonym: ember-resistant vent.
Related
Where this term is used
- Bird blocks, boxed soffit, or unvented attic
- California AB 38 seller disclosure
- Chimney spark arrestors
- Craftsman eaves under R327
- Deck railings in the WUI
- Dryer vents versus mesh
- Ember versus flame versus radiant heat
- How an intumescent vent closes