WOOD SPECIAL INSPECTIONS ACCORDING TO THE IBC CODE

Does the International Building Code (IBC) require special inspections on wood construction elements during the construction phases of a new project? The answer is YES; however, the frequency of special inspections and what specific code compliance criteria to apply according to the IBC code can be challenging to ascertain.

IBC Chapter 17, “Special Inspections and Tests,” Section 1705.5, specifies special inspections of prefabricated wood structural elements and assemblies. The verbiage of Section 1705.5 invokes Sections 1704.2.5, 1703.6, and 1704.2.5.1, and merely reading these four sections will make your head spin and may cause you to swear out loud. However, all four sections (listed below) are essential sources of wood code compliance criteria.

• 1705.5 Wood construction. Special inspections of prefabricated wood structural elements and assemblies shall be in accordance with Section 1704.2.5. Special inspections of the site-built assemblies shall be in accordance with this section. The fabrication process of wood structural elements and assemblies (such as wood trusses) that are being performed on the premises of a fabricator’s shop must have special inspections in accordance with Section 1704.2.5.
• 1704.2.5 Special inspections of fabricated items. Where fabrication of structural load-bearing or lateral load-resisting members or assemblies is being conducted on the premises of a fabricator’s shop, special inspections of the fabricated items shall be performed during fabrication, except where the fabricator has been approved to perform work without special inspections in accordance with Section 1704.5.1. Inspection of in-plant fabrications and the requirements for special inspections are addressed in Section 1704.2.5. This section should be used in conjunction with Section 1703.6 relating to evaluation and follow-up inspections. The special inspector is required to verify not only that the fabricator complies with the design details and in-house quality control procedures at the plant, but also that the plant has the capability to construct/fabricate according to the approved drawings, standards and specifications.
• 1703.6 Evaluation and follow-up inspection services. Where structural components or other items regulated by this code are not visible for inspection after completion of a pre-fabricated assembly, the owner or owner’s authorized agent shall submit a report of each prefabricated assembly. The report shall indicate the complete details of the assembly, including a description of the assembly and its components, the basis upon which the assembly is being evaluated, test results and similar information and other data as necessary for the building official to determine conformance with this code.
• 1704.2.5.1 Fabricator approval. Special inspections during fabrication are not required where the work is done on the premises of a fabricator approved to perform such work without special inspection. Approval shall be based on review of the fabricator’s written fabrication procedures and quality control manuals that provide a basis for control of materials and workmanship, with periodic auditing of fabrication and quality control practices by an approved agency or the building official. At completion of fabrication, the approved fabricator shall submit a certificate of compliance to the owner or the owner’s authorized agent for submittal to the building official as specified in Section 1704.5 stating that the work was performed in accordance with the approved construction documents.

The term “approved fabricator” is defined in IBC Section 202, and this section provides the basis for such approval by the building official. An approved fabricator has received authorization to perform work without a code-required special inspection. This approval is based on the review of the fabricator’s written procedural and quality control (QC) manuals and periodic auditing of fabricating practices by an approved special inspection agency; it is often obtained through a third-party testing agency that visits the fabrication shop to review the QC system and individuals involved in the fabrication process. These fab shop visits are usually provided at least twice per year. The alternative to these shop inspection visits is that the fabricator is enrolled in a nationally accepted inspection or accreditation program acceptable to the registered design professional in responsible charge; these accreditation programs generally require a minimum of two fab shop inspection tours annually.

In addition to IBC Chapter 17, IBC Chapter 23, entitled “Wood,” also presents IBC code required compliance criteria. The general scope of IBC Chapter 23 is to stipulate provisions that govern the materials, design, construction, and quality of wood members and their fasteners. Chapter 23 is not a textbook on construction; it is assumed that the reader has the training and experience to understand the principles and practices of wood design and construction. Without such understanding, some sections may be misunderstood and misapplied. IBC offers much commentary to help promote a better understanding of the structure and application of the methods specified in Chapter 23.

Section 2302 of Chapter 23 identifies three methods of design, and compliance with one or more of these methods is required. Section 2302 also references manufacturing standards, necessary specification criteria, and use and application provisions.

Section 2304 contains general provisions for the proper design and construction for all wood structures and the use of all wood products. Note that the general provisions of Section 2304 apply to all design methods. This section also includes the typical fastening schedule, which is the minimum requirement for fastening various wood members.

Section 2305 references the American Wood Council (AWC) Special Design Provisions for Wind and Seismic (SDPWS) for the design of lateral-force-resisting systems. It also contains provisions not found in the standard, such as design values for staples. Whether the structure is engineered using allowable stress design (ASD) or load and resistance factor design (LRFD), the provisions of this section apply to the design of the lateral-force-resisting system.

Section 2306 contains provisions for the design of structures using ASD and references applicable standards. The two primary design standards are the AWC National Design Specification for Wood Construction and SDPWS. Historically, all of the industry publications have been developed for ASD.

More recently, LRFD has been introduced, making it necessary to distinguish which provisions are appropriate for ASD or LRFD. Because the American National Standards Institute (ANSI) AWC NDS and SDPWS are dual-format standards permitting both ASD and LRFD design procedures, Section 2307 also references these consensus standards for the design of structures using the LRFD methodology.

IBC Chapter 23 consists of 120 pages of varied code compliance criteria and covers practically every phase of different types of wood construction. It is detailed and complex; the verbiage is only reader- friendly if the reader is trained and experienced in wood construction. This chapter is jam-packed with compliance criteria and addresses topics from grading and uses of lumber types, nailing patterns and staple requirements, preservative-treated wood standards, and minimum structural/design criteria. Any wood special inspector should be familiar with and knowledgeable of the content of IBC Chapter 23.

TALL WOOD BUILDINGS AND THE USE OF PODIUMS

We should all expect to see more tall wood buildings in the future. Podium construction, also known as pedestal construction, is a common approach to mid-rise, multi-family, and mixed-use developments. Until recently, podium construction has typically included multiple stories of light-frame wood construction built over a single or multi-story Type 1A podium constructed of noncombustible steel or cast-in-place concrete. The podium portion of the project often comprises retail, parking, or mixed-use building classifications.

The 2021 edition of the IBC code introduces new construction types, which allows podium-type construction to include tall mass timber buildings as an option (IBC 2021, Chapter 5). In contrast to light-frame wood construction, mass timber construction is built using engineered wood products typically made of large, solid wood panels, columns, or beams often manufactured off-site for load-bearing wall, floor, and roof construction.

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Trouble deciphering the code? Call the Experts at F&R: Alan S. Tuck, Director of Code Compliance & Training T 540.344.7939 | M 540.798.4440 | [email protected]