The figure depicts an unprotected portion of the mass timber ceiling . For Type IV-B construction, Section 602.4.2.2.2, Exception 1.1, limits unprotected ceiling areas—including attached mass timber beams—to 20 percent of the floor area of the applicable dwelling unit or fire area. Option B is therefore correct.

The percentage is based on floor area rather than total ceiling surface area. For example, where the associated fire area contains 1,000 square feet of floor area, the maximum ceiling exposure permitted under this particular exception would be 200 square feet, subject to the additional separation and mixed-exposure provisions.

The 40-percent value in option D applies to mass timber walls, including attached columns , rather than ceilings. The 15-percent and 30-percent values are not the prescribed Type IV-B ceiling exposure limitations in the 2021 IBC.

The inspector must additionally determine whether another exposed wall or ceiling region exists nearby. Section 602.4.2.2.4 imposes a 15-foot separation requirement, and Section 602.4.2.2.3 controls situations where both wall and ceiling surfaces are intentionally exposed.

References/Topics: 2021 IBC Sections 602.4.2.2.2 through 602.4.2.2.4; Type IV-B ceiling exposure limitations.

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Option C is not an IFC requirement. The 2021 IFC requires inspection records to be maintained on-site, but it does not require those records to be secured in a fire- and water-resistant safe.

Section 3303.2 requires the owner to designate a site safety director. Section 3303.3 then makes that director responsible for completing a daily fire safety inspection of the project site. Every day, building and outdoor construction areas must be evaluated against the prescribed fire-safety inspection items.

The results of each inspection must be documented and retained on-site until a certificate of occupancy has been issued . The records must also be immediately available at the site for presentation to the fire code official upon request. Options A, B, and D therefore accurately reflect the code requirements.

The daily inspection program covers practical hazards such as hot work, temporary heating, combustible debris, temporary electrical wiring, hazardous-material storage, fire apparatus access, hydrants, fire department connections, standpipe availability, and portable extinguishers.

For tall mass timber projects, this documentation is particularly important because substantial combustible construction may be present before permanent fire protection systems are complete.

References/Topics: 2021 IFC Sections 3303.2 and 3303.3; site safety director; daily fire-safety inspection and documentation.

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The 2 × 2 block is intended to protect the abutting wood edges from the effects of char contraction. Therefore, option D is correct.

During fire exposure, wood chars and the char layer can shrink or contract. At an interface between two abutting timber components, that contraction can create a gap that allows heat and flames to penetrate deeper than predicted for a continuous exposed surface. AWC connection-fire-design methodology therefore requires additional protection at susceptible joints and interfaces. The block shields the abutting edges and maintains the sacrificial wood-cover path around the protected connection.

Its primary function is not decorative, nor is it simply an air-sealing component. Although limiting airflow can be a secondary consequence of closing the interface, the design purpose addressed by the technical guidance is control of premature fire penetration caused by char contraction. The block also should not be interpreted independently as a generic one-hour protective membrane for the steel ledger; the connection’s total rating depends on the complete approved protection assembly.

The inspector should confirm the block’s dimensions, species or product designation, fastening, continuity, and tight installation before the connection is concealed.

References/Topics: AWC Technical Report 10; AWC Fire Design Specification provisions addressing char contraction and gaps between abutting wood members.

ASTM C920 is the required standard for sealants used under the IBC mass timber air-sealing provision. Option C is therefore correct. Section 703.7 applies to Type IV-A construction and requires compliant sealant or adhesive at specified interfaces involving fire-resistance-rated mass timber elements.

The sealing requirement reduces the movement of air, heat, and combustion gases into gaps that could expose additional timber surfaces and undermine the rated performance assumed by the approved design. The sealant must not merely appear to close the opening; it must be the specified product and installed within its approved joint dimensions and substrate conditions.

ASTM A36 is a structural steel material specification. ASTM E119 establishes procedures for fire testing building construction and assemblies but does not qualify elastomeric sealant products. ASTM F1667 covers driven fasteners such as nails, spikes, and staples and has no application to this sealing requirement.

Under Section 1705.20, installation is subject to periodic special inspection where the Section 703.7 sealant is applied. Inspection should occur before concealment and confirm continuity, adhesion, backing, joint depth, surface cleanliness, and compliance with the approved documents.

References/Topics: 2021 IBC Sections 703.7 and 1705.20; Type IV-A construction; ASTM C920.

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