93-Tall-Mass-Timber-Buildings International Code Council Exam Lab Questions

The connection detail specifies the CLT-to-glulam screws at 24 inches on center , so option D is correct. This is a construction-document interpretation question rather than a universal prescriptive screw-spacing requirement imposed by the IBC.

The approved structural detail controls the required spacing for this particular connection because the registered design professional has established the connection geometry and fastener schedule based on the applicable structural loads, CLT panel configuration, glulam member, fastener properties, and required load transfer. The 24-inch dimension must therefore be maintained in the field unless an approved revision changes the connection design.

IBC Table 1705.5.3 is directly relevant to the special inspector’s responsibilities. For screws used in Type IV-A, IV-B, or IV-C mass timber connections, periodic special inspection includes verification of diameter, length, head type, spacing, installation angle, and installation depth . The special inspector is therefore expected to compare actual field installation against precisely this type of approved connection detail.

Substituting 12-, 16-, or 20-inch spacing without design authorization would constitute a deviation from the approved documents, even if the alternate spacing appeared more conservative.

References/Topics: Approved structural connection detail shown in the exhibit; 2021 IBC Section 1705.5.3 and Table 1705.5.3, inspection of screw spacing and installation.

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ICC-ES ESR-1539 is the applicable evaluation report, making option C correct. ESR-1539 addresses nails and staples manufactured by participating companies and evaluates their use in engineered and nonengineered structural connections.

An ICC-ES Evaluation Report provides evidence that a proprietary product or system complies with specified building-code requirements where the product does not rely solely on the generic prescriptive provisions of the IBC. For proprietary nails, the report provides the technical basis needed to establish characteristics such as dimensions, materials, recognized structural applications, allowable design values, installation limitations, and conditions of use.

The current ICC-ES document is published as ESR-1539P, reflecting subsequent administrative updates to the report, but the identifying evaluation-report number remains 1539 , matching option C and the examination question.

For special inspection, merely recognizing the ESR number is not enough. The inspector should verify that the installed proprietary fastener is actually included in the report, that its diameter and length correspond to the approved construction documents, and that installation spacing, penetration, orientation, substrate, and other report conditions are satisfied.

References/Topics: ICC-ES ESR-1539, structural nails and staples; proprietary fastener evaluation and installation requirements. ICC-ES states that the nails and staples covered by ESR-1539 are used in engineered and prescriptive structural connections.

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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IBC Section 722.7 establishes the governing calculation principle for protected mass timber. The required fire resistance consists of the inherent fire resistance of the unprotected mass timber element plus the protection time contributed by the noncombustible protection . Therefore, option D is correct.

This approach recognizes two sequential protective mechanisms. First, the noncombustible covering delays heating and charring of the timber. After the credited protection period, the remaining mass timber cross section provides structural fire resistance through predictable charring behavior and residual section capacity. Section 722.7.1 further requires the contribution of the covering material to comply with the prescribed protection times or to be established under Section 703.6.

Option A ignores the contribution of the protective membrane. Option B ignores the inherent structural fire resistance of the timber. Option C incorrectly substitutes a finish rating for the code-recognized protection contribution. A finish rating is a separate temperature-based performance concept and is not automatically additive as the protection time used by Section 722.7.

References/Topics: 2021 IBC Sections 602.4, 703.6, 722.7 and 722.7.1; calculation of protected mass timber fire resistance.

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