Free Practice Questions for International Code Council 93-Tall-Mass-Timber-Buildings Exam

Type IV-C generally permits interior mass timber surfaces to remain exposed, but shaft and elevator hoistway enclosures are a specific exception to that broad exposure allowance. Section 602.4.3.6 requires shafts, elevator hoistways, and interior exit stairway enclosures constructed with mass timber to receive noncombustible protection having a minimum assigned protection time of 40 minutes . Option A is therefore correct.

Critically, protection is required on both the inside and outside of the shaft enclosure . The 40-minute value is an assigned contribution from the noncombustible protection; the complete enclosure must still satisfy whatever overall fire-resistance rating is required by Sections 713, 713.4, Table 601, or other applicable provisions.

Option B incorrectly applies the general Type IV-C exposed-interior allowance to a specifically regulated shaft condition. Option C is incomplete because 1/2-inch Type X gypsum board provides only 25 minutes under Table 722.7.1(2), not the required 40 minutes. A 5/8-inch Type X board provides a recognized 40-minute contribution when installed in accordance with Section 722.7.2. Option D does not state the prescribed Type IV-C shaft requirement.

References/Topics: 2021 IBC Sections 602.4.3.2 and 602.4.3.6; Tables 722.7.1(1) and 722.7.1(2).

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IBC Table 601, Footnote “a,” permits a one-hour reduction in the required fire-resistance rating of the primary structural frame and bearing walls where those elements support a roof only. Option C is therefore correct.

For Type IV-C construction, the normal Table 601 requirement for bearing walls is two hours. Where a bearing wall qualifies as supporting only roof construction, application of the footnote permits that rating to be reduced from two hours to one hour.

The limitation “supporting a roof only” is critical. The reduction cannot be applied simply because a wall is located at the uppermost occupied level. If the wall carries a floor, mezzanine, transfer load, occupied rooftop structure, or another structural element beyond qualifying roof construction, the condition for the reduction is not satisfied.

Options A and B are not reductions prescribed by Table 601. Option D would effectively eliminate the entire normal two-hour Type IV-C bearing-wall rating, which the footnote does not permit.

For inspection purposes, the approved construction documents and structural load path must substantiate use of the reduction. The fire-protection installation should then be checked against the actual reduced rating specifically authorized by the design.

References/Topics: 2021 IBC Table 601, Footnote “a”; Type IV-C bearing walls supporting roof construction only.

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Option A is the exception because the base fire-resistance rating for an exterior bearing wall in Type IV-C construction is two hours, not one hour. The values are established by 2021 IBC Table 601.

Type IV-A has the most stringent tall mass timber construction requirements and assigns a three-hour rating to exterior bearing walls. Type IV-B and Type IV-C each assign a two-hour rating. Consequently, options B, C, and D accurately state the Table 601 requirements, while option A understates the required rating by one hour.

The Table 601 value is the minimum construction-type rating. Exterior bearing walls must also comply with the exterior-wall requirements of Table 705.5 based on fire separation distance. Where another code provision requires a higher rating, the more restrictive requirement governs. The inspector must therefore avoid treating the two-hour Type IV-C value as an absolute maximum.

Field verification should include the approved wall assembly, mass timber dimensions, noncombustible exterior protection, membrane continuity, protection of connections, intersections, joints, and any required opening protection. An exterior bearing wall installed as a nominal one-hour assembly would not comply merely because the timber itself has substantial cross-sectional dimensions.

References/Topics: 2021 IBC Table 601; Sections 602.4 and 705.5; exterior bearing-wall ratings for Types IV-A, IV-B, and IV-C.

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Adhesives installed to resist air passage at qualifying mass timber interfaces must comply with ASTM D3498. Therefore, option C is correct. IBC Section 703.7 applies this requirement to Types IV-A, IV-B, and IV-C at prescribed abutting edges and intersections of building elements that require fire-resistance ratings.

ASTM D3498 addresses adhesives used for field-gluing wood-based structural components. Compliance is significant because the adhesive must retain adequate bond performance under the environmental and service conditions associated with the approved application. The special inspector should verify product identification, compatibility with the timber substrate, manufacturer instructions, storage conditions, shelf life, surface preparation, application temperature, coverage, and curing.

UL 263 is a fire-resistance test standard for building assemblies and structural elements; it is not the product standard for the adhesive. ASTM A653 applies to metallic-coated steel sheet. ASTM F1575 concerns pressure-sensitive safety glazing films and is unrelated to sealing mass timber interfaces.

Where the adhesive is required by Section 703.7, its installation is subject to periodic special inspection under Section 1705.20 unless the applicable code exception removes the sealing requirement.

References/Topics: 2021 IBC Sections 703.7 and 1705.20; ASTM D3498; Type IV-C sealing requirements.

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