Section 718.1/Concealed Spaces (Fireblocking and Draftstopping)
IBC 718 covers fireblocking and draftstopping requirements in concealed spaces within walls, floors, and attics to prevent the spread of fire and hot gases through hidden cavities.
Section 718.2 requires fireblocking to cut off concealed spaces both vertically and horizontally. Fireblocking is required: in stud walls at each ceiling and floor level and at 10-foot vertical intervals; at all interconnections between concealed vertical and horizontal spaces (soffits, drop ceilings, cove ceilings); at openings around vents, pipes, ducts, and chimneys at ceiling and floor level; at stairway stringers at the top and bottom; and at connections between concealed spaces and chimneys. Approved materials include 2-inch nominal lumber, structural wood panels, gypsum board, cement fiber board, and mineral wool batts. Section 718.3 covers draftstopping in floor-ceiling assemblies and attic spaces of combustible construction, dividing concealed spaces into areas not exceeding specified limits (1,000 square feet for attics in Group R-2, 3,000 square feet for floor-ceiling assemblies).
Why this section exists
Concealed spaces within walls, floors, and attics act as flues that channel fire and hot gases. A fire starting in a first-floor wall can travel vertically through the stud cavity to the attic in minutes. Fireblocking interrupts these pathways. Draftstopping subdivides large concealed spaces to slow lateral fire spread. These requirements are particularly critical in wood-framed construction where the framing itself is combustible.
What plan reviewers look for
Plan reviewers check wall sections, floor sections, and attic plans for fireblocking locations. They verify fireblocking at every floor and ceiling level in stud walls. They check for fireblocking at soffits, drop ceilings, and cove ceilings. For Group R-2 (apartments), they check attic draftstopping at 1,000 square foot intervals aligned with dwelling unit separations. They verify the fireblocking material is an approved type. They check that through-penetration firestops are not confused with fireblocking.