Types of Construction for Buildings as per Table 503

Types of Construction for Buildings as per Table 503

as referred to by IBC Table 503

In most typical residential construction, with no fire sprinkler system or fire rated coatings or coverings, you are working with a Type Five B construction. Table 503 limits this Type Five B to Two Stories, 35′ Maximum Building Height and an area not to exceed 4,800 sq. ft. By adding the protection of a fire rated coatings or coverings, now a Type Five A. you are limited to 3 Stories, 40′ Maximum Building Height and an area of 10,200 sq. ft.

Type I (fire resistive) Least combustible

Type III (ordinary)

Type IV (heavy timber)

Type V (wood frame) Most combustible

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TYPE I — This concrete and steel structure, called fire resistive when first built at the turn of the century, is supposed to confine a fire by its construction. This type of construction in which the building elements listed in IBC Table 601 are of noncombustible materials such as concrete and steel. The roof is also of noncombustible material such as concrete or steel .

TYPE II — This type building has steel or concrete walls, floors and structural framework similar to a type I construction however, the roof covering material is combustible. The roof covering of a type II building can be a layer of asphalt water proofing, with a combustible felt paper covering. Another layer of asphalt may be mopped over the felt paper.

TYPE III — This type of constructed building is also called a brick and joist structure by some. It has masonry bearing walls but the floors, structural framework and roof are made of wood or other combustible material. For example; a concrete block building with wood roof and floor trusses. Fire-retardant-treated wood framing complying with IBC Sec. 2303.2 shall be permitted within exterior wall assemblies of a 2-hour rating or less.

TYPE IV — These buildings have masonry walls like Type III buildings but the interior wood consists of heavy timbers. In a heavy-timber building a wood column cannot be less than eight inches thick in any dimension and a wood girder cannot be less than six inches thick. The floor and roof are plank board. One difference between a heavy timber type IV building and type III construction is that a heavy-timber type IV building does not have plaster walls and ceilings covering the interior wood framework. The details of type IV construction shall comply with the provisions of 602.4.1 through 602.4.7. Fire-retardant-treated wood framing complying with IBC Section 2303.2 shall be permitted within exterior wall assemblies with a 2-hour rating or less.

TYPE V — Wood-frame construction is the most combustible of the five building types. The interior framing and exterior walls may be wood. A wood-frame building is the only one of the five types of construction that has combustible exterior walls. This is the typical single-family home construction method. These buildings are built with 2×4 or 2×6 studs and load bearing walls, wood floor trusses or wood floor joist and wood roof framing.

Protected A means that all structural members of a building or structure has additional fire rated coating or cover by means of sheetrock, spray on, or other approved method. This additional fire rated coating or cover extends the fire resistance rating of structural members at least 1 hour.

Un-protected B means that all structural members of a building or structure has no additional fire rated coating or cover.

If you’re having to fill out on a building permit application for a single family residence new construction, the Maximum Allowable Building Height for a Type Five B construction according to Table 503, the answer is, 2 Stories in Floors and 35′ in Building Height and an Allowable Floor Area of 4,800 sq. ft. I have had some cities say the Allowable Floor Area is Air-Conditioned Floor Space, some say it’s Enclosed which would be Living Area plus the Garage and the others say it’s the Total Area Under Roof. You will have to check with your own Building Permit Office to see which might apply to you.


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