Framing & StructuralQuestion 316 of 700

Which material is generally ACCEPTABLE as fireblocking in a concealed stud space?

a.Loose sawdust
b.Nominal 2-inch lumber fitted to the opening
c.A sheet of ordinary polyethylene film
d.Uncased fiberglass batts hung loosely in the cavity

Explanation

Approved fireblocking includes 2-inch nominal lumber cut to fit, two thicknesses of 1-inch lumber, wood structural panels, gypsum board, and certain mineral or approved materials. Loose sawdust and thin polyethylene are combustible or ineffective, and unsupported batts alone are not accepted general fireblocking except where specifically permitted.

Law Reference: 2025 CA Residential Code §R602.8

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