International Code Council 93-Tall-Mass-Timber-Buildings - 93-Tall-Mass-Timber-Buildings

ASTM E84 is not a test for establishing the fire-resistance rating of a structural member or building assembly. Therefore, option B is the exception.

The 2021 IBC establishes fire-resistance ratings primarily through testing conducted in accordance with ASTM E119 or UL 263. Those tests evaluate whether an element or assembly can maintain structural performance, limit flame passage, and control temperature rise for a specified duration under standardized fire exposure. ASTM E84 instead evaluates surface-burning characteristics, principally flame-spread and smoke-developed indices. An E84 classification cannot establish that a wall, floor, beam, column, or connection possesses a one-, two-, or three-hour fire-resistance rating.

The IBC also recognizes approved prescriptive designs under Section 721, calculated fire resistance under Section 722, and designs documented in approved sources or supported by permitted analytical methods. Those are valid methods represented by options A, C, and D.

For inspection purposes, the approved construction documents must identify the method used to establish the rating. The inspector must then verify that the installed materials, dimensions, loading assumptions, protective layers, fasteners, joints, and connection details match the tested, calculated, or prescriptive design.

References/Topics: 2021 IBC Sections 703.2, 703.2.1, 721 and 722; ASTM E119 and UL 263 fire-resistance testing.

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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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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 governing standard is ANSI/APA PRG 320, Standard for Performance-Rated Cross-Laminated Timber. Therefore, option A is correct. The 2021 IBC requires structural glued cross-laminated timber to be manufactured and identified in accordance with PRG 320, and Type IV provisions require CLT to bear a label demonstrating conformity with that standard.

PRG 320 addresses essential manufacturing and qualification requirements, including panel construction, layup, structural performance, adhesive qualification, dimensional tolerances, product marking and quality assurance. Product identification is particularly important to the special inspector because visual similarity alone does not establish that a panel is code compliant.

DOC PS 2 applies primarily to wood structural panels such as plywood and oriented strand board and is not the manufacturing standard for CLT. ANSI/AITC or ANSI/APA A190.1 applies to structural glued-laminated timber, commonly called glulam. ASTM D5055 covers the establishment and monitoring of structural capacities for prefabricated wood I-joists.

The inspector should verify that CLT panels retain legible identification and that the manufacturer, grade, layup and panel designation correspond to the approved construction documents.

References/Topics: 2021 IBC Sections 602.4 and 2303.1.4; Chapter 35; ANSI/APA PRG 320-2019.

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