Pass the International Code Council Special Inspector 93-Tall-Mass-Timber-Buildings Questions and answers with CertsForce

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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The construction detail identifies a 1/2-inch tolerance between the steel beam web and the adjacent CLT panel. Therefore, option B is correct.

This is principally a construction-document interpretation question rather than a generic prescriptive IBC dimension. The 2021 IBC does not establish one universal steel-web-to-CLT clearance applicable to every mass timber connection. The required clearance is project specific and is established by the registered design professional through the approved structural drawings and connection details.

The tolerance provides erection clearance for placement of the prefabricated CLT around the steel member while accounting for fabrication and installation variation. It must not be arbitrarily reduced or increased because the gap can affect panel fit, bearing conditions, fastener alignment, fire-protection continuity, acoustic treatment and any specified joint-filling material.

Under the special-inspection framework, the inspector must compare the installed connection directly with the approved construction documents. Any condition that does not maintain the specified 1/2-inch clearance—or any undocumented field modification to the CLT or steel connection—must be reported and resolved through the registered design professional rather than accepted solely on the contractor’s direction.

References/Topics: Approved structural details; 2021 IBC Sections 1704.2 and 1705.5; inspection of mass timber erection, anchorage and connections.

Option D directly reflects the engineering-analysis method authorized by 2021 IBC Section 2304.10.1. For structural connections in Type IV-A, IV-B, or IV-C construction, the analysis must demonstrate that temperatures at every relevant portion of the connection remain within prescribed limits for a period corresponding to the fire-resistance rating required of the connected structural element.

The code establishes two critical temperature-rise limits: an average rise of not more than 250°F and a maximum rise of not more than 325°F . For this purpose, the “connection” includes the connectors, fasteners, and those portions of the wood members that participate structurally in the connection.

Option A is incorrect because ASTM E136 is a test for determining whether a material is noncombustible; it is not the fire-resistance test method for a structural connection. Option B is not a code-recognized substitute for the required connection fire evaluation. Option C is insufficient because a manufacturer’s generalized fire-performance representation does not establish the required code fire-resistance duration unless supported through an approved test, evaluation, or engineering analysis.

References/Topics: 2021 IBC Section 2304.10.1; engineering-analysis method for Type IV-A, IV-B, and IV-C structural connections.

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IBC Table 601 requires floor construction and associated secondary structural members in Types IV-A, IV-B, and IV-C construction to have a two-hour fire-resistance rating. Therefore, option B is correct.

This requirement applies to the complete floor assembly, not only the timber panel. The required two-hour performance may be established through the calculated fire resistance of the mass timber, the contribution of approved noncombustible protection, or a permitted combination of both. Any topping, protective membrane, connection protection, and edge condition that forms part of the approved rated design must be installed accordingly.

The ratings for other building elements should not be transferred to the floor. A three-hour rating applies to the primary structural frame and bearing walls of Type IV-A, but its floor construction remains two hours. Type IV-B and Type IV-C floors also require two hours, even though those construction types permit different degrees of exposed mass timber.

The special inspector must verify panel dimensions, approved layup, protection layers, joints, penetrations, connections, topping thickness, and other details that influence the floor’s rated performance.

References/Topics: 2021 IBC Sections 601 and 602.4; Table 601, floor construction and associated secondary structural members.

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