Sealing Dropped Soffits/Bulkheads

Select sealants that:

are compatible with their intended surfaces,

allow for differential expansion and contraction between dissimilar materials,

meet the requirements of the applicable fire safety code (e.g. thermal or ignition barriers), and

for use inside the pressure boundary select low volatile organic compound (VOC) sealants that meet independent testing and verification protocols

Select materials that:

adequately support applied load and are permanent air barriers,

meet the requirements of the applicable fire safety code (e.g. thermal or ignition barriers), and

for use inside the pressure boundary select low volatile organic compound (VOC) materials that meet independent testing and verification protocols

Install support material for spans wider than 24", except when air barrier material is rated to span greater distance under load (e.g., wind, insulation)

Support material installed for any walking/working surface (attics or floors) will support the weight of a worker and any insulation applied in the area

Remove any material from the sealing area that will prevent full adhesion of the selected sealant

Install rigid air barrier material over the entire soffit opening in alignment with the attic's pressure boundary

Mechanically fasten air barrier material to prevent movement

Apply a continuous seal at all seams, cracks, joints, edges, penetrations, and connections of the soffit while applying sufficient pressure to push sealant into any gaps or cracks and contact any backing or infill material required

Install only noncombustible materials and sealants with an ASTM E136 listing in contact with any device producing 200 degrees F or more (chimneys, vents, flues, etc.)