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Conventional Construction Provisions of the 2006 International Building Code: An Illustrated Guide is a comprehensive guide that explains in detail the conventional construction provisions in Chapter 23 of the 2006 International Building Code. Descriptive discussion and illustrations convey the prescriptive provisions related to conventional wood-framed construction. An essential publication for professionals involved in the design, construction, plan review or inspection of wood-framed structures.
Excerpt from the Introduction
In very general terms, wood construction came long before engineering design and analysis; therefore, there is a large residual body of building methods and techniques that have withstood the test of time, satisfying standards of structural stability without additional substantiating data. These are the traditional modes of construction we call conventional, and we accept their worth, within the prescribed limits, without further challenge.
Prescriptive conventional construction provisions originated with the repetitive light-frame wood construction provisions of the Uniform Building Code (UBC). Early editions of the UBC had a section entitled "wood-joisted dwelling construction" that later became "light-frame construction" and was later changed to "conventional construction provisions" in the 1970 UBC. The term "conventional construction" that we use today first originated with the 1970 UBC. The conventional construction provisions have always been entirely prescriptive and were intended to apply to buildings constructed of repetitive light-wood framing members consisting of studs, joists, and rafters.
The word "prescription" means "the action of laying down authoritative rules or directions." The word "prescriptive" means "acquired by, founded on or determined by prescription or by long-standing custom." Together these two definitions clearly describe the nature of the conventional wood-frame construction provisions in the International Building Code: they are a set of rules based on long-standing custom.
An essential feature of the conventional construction provisions is in this statement: "Other methods may be used provided a satisfactory design is submitted showing compliance with other provisions of this code." In other words, one need not conform to the restrictions, limitations and requirements of the provisions if a design is submitted to the jurisdiction that conforms to the engineering requirements of the code. In summary, wood frame buildings must either conform to the restrictions, limitations and requirements prescribed in the conventional construction provisions, or engineering must be provided that demonstrates compliance with the engineering requirements of the code.
Section 2308 of the 2006 International Building Code (IBC) limits the use of conventional, light-frame wood construction as follows:
1. Buildings shall be limited to a maximum of three stories above grade. For the purposes of this section, for buildings in Seismic Design Category D or E as determined in Section 1613.5.6, cripple stud walls shall be considered a story.
EXCEPTION: Solid blocked cripple walls not exceeding 14 inches (356 mm) in height need not be considered a story.
2. Bearing wall floor-to-floor heights shall not exceed 10 feet (3048 mm) plus floor framing height not to exceed 16 inches (406 mm).
3. Loads as determined in Chapter 16 shall not exceed the following:
3. 1. Average dead loads shall not exceed 15 psf (718 N/m2) for roofs and exterior walls, floors, and partitions.
3.2. Live loads shall not exceed 40 psf (1916 N/m2) for floors.
3.3 Ground snow loads shall not exceed 50 psf (2395 N/m2)
4. Wind speeds shall not exceed 100 mph (161 km/hr) (3-second gust).
EXCEPTION: Wind speeds shall not exceed 110 mph (177 km/hr) 3-second gust for buildings in Exposure Category B.
5. Roof trusses and rafters shall not span more than 40 feet (12 192 mm) between points of vertical support.
6. The use of the provisions for conventional light-frame construction in this section shall not be permitted for buildings in Seismic Design Category B, C, D, E or F for buildings in Occupancy Category IV, as determined in Section 1604.5.
7. Conventional light-frame construction is limited in irregular structures in Seismic Design Category D or E, as specified in Section 2308.12.6.
In order to provide for typical methods of construction without requiring a complete structural design, the International Building Code also includes prescriptive provisions for footings supporting conventional light-frame construction in Chapter 18, Soils and Foundations. The building official may use Section 1604.1 in order to accept these conventional light-frame construction provisions in lieu of engineering design.
Chapter 23 includes tables showing the allowable spans for structural elements of a common wood-frame building. As mentioned before, care should be exercised when determining which buildings to accept under these provisions; the buildings should be conventional light-frame types of construction. A common quandary exists as to whether or not construction that contains engineered trusses should be included in this category. The International Building Code addresses the use of wood trusses in conventional wood-frame construction. Sections 2303.4 and 2308.10.10 allow trusses to be used in conventional wood-frame construction, provided that these members are designed in accordance with the requirements of Chapter 23 and accepted engineering practice. In other words, the building official must be provided with justification (calculations and detailed plans, etc.) for the use of trusses in conventional wood construction. See Section 2303.4 for specific requirements pertaining to engineered trusses.
Chapter 23 addresses specific conventional light-frame wood construction in areas subject to wind speeds less than or equal to 100 mph (3-second gust) and moderate to major earthquake risk activity in Seismic Design Categories B, C, D and E. Note that the permissible wind speed is 110 mph for buildings sited in Exposure Category B.
This publication is designed in such a way that you, as an inspector or contractor, performing rough wood-framing inspections or construction, will have at your fingertips relevant code provisions, a brief commentary, and, where applicable, figures that illustrate the conventional wood-frame construction provisions of the IBC.
The format of this document presents the code text in italics, with a brief narrative presented in normal text.
This guide is designed to assist in understanding and applying the general code provisions governing conventional light-frame wood construction. To accomplish this task, the manual includes information that is not contained within the International Building Code provisions regulating conventional light-frame wood construction; however, these nonconventional provisions are necessary in order to provide you with a complete perspective of the intent of the conventional construction provisions.
Table of Contents
Introduction. Size of Structural Member. General Construction Provisions. Conventional Light-Frame Construction Provisions. Seismic/Wind - Wall Bracing. Floor Joists. Girders and Headers. Wall Framing. Rafter/Ceiling Joists. |
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