93-Tall-Mass-Timber-Buildings International Code Council 93-Tall-Mass-Timber-Buildings Free Practice Exam Questions (2026 Updated)

IBC Table 601 requires both exterior and interior bearing walls in Type IV-C construction to have a minimum two-hour fire-resistance rating. Option B is correct.

For exterior bearing walls, the Table 601 rating is not the only applicable criterion. Section 602.1 also requires exterior walls to satisfy Table 705.5 based on occupancy and fire separation distance. Where Table 705.5 or another provision imposes a more restrictive rating, the higher requirement governs.

The two-hour rating may be achieved through the calculated structural fire resistance of the mass timber, approved noncombustible protection, or an approved combination of the two. Connections, intersections, penetrations, and abutting edges must not create a premature failure path or compromise the rated assembly.

A one-hour reduction can be permitted for bearing walls supporting a roof only under Table 601, Footnote “a,” but that exception does not apply to a wall carrying floors or other qualifying structural loads. The inspector must confirm the actual load path before accepting any reduced protection at the uppermost level.

References/Topics: 2021 IBC Sections 601, 602.1 and 602.4; Tables 601 and 705.5; Type IV-C bearing walls.

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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When the footnotes are disregarded, the fire-resistance ratings assigned to the principal building elements of Type IV-A construction correspond to those of Type I-A construction . Option A is therefore correct.

IBC Table 601 assigns both Type I-A and Type IV-A a 3-hour rating for the primary structural frame , 3 hours for exterior and interior bearing walls, 2 hours for floor construction and associated secondary structural members , and 1½ hours for roof construction and associated secondary structural members . Interior nonbearing walls and partitions are generally rated zero by Table 601 unless another code provision requires a rating. Exterior nonbearing walls are governed separately based on fire separation distance.

The similarity in Table 601 ratings does not mean Type I-A and Type IV-A are otherwise equivalent construction types. Type I-A relies principally on noncombustible structural construction, whereas Type IV-A permits mass timber subject to the substantial noncombustible protection requirements of Section 602.4.1.

Types II-A, III-A, IV-C, and IV-HT have materially different Table 601 requirements, so options B, C, and D do not provide a complete rating match.

References/Topics: 2021 IBC Section 601 and Table 601; Types I-A and IV-A fire-resistance ratings.

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