The International Building Code (IBC) categorizes buildings into five types of construction, and each has different parameters. The primary purpose of categorizing various types of construction is to establish a basic level of safety for occupants in the event of a fire. Secondary is the preservation of the property itself.
Ultimately, the type of construction drives the building’s use, occupant load, square footage, height, proximity to other structures, windows, exit placements, fire resistance, and the need for sprinklers.
Determining which of the five types of construction your project falls under is a key decision as part of the scoping process with your construction manager and building designer. You’ll want to work with them to clearly outline your needs and requirements before you get too deeply involved in the planning details.
Type I is the most stringent construction for a building. Building materials and practices used in Type I construction provide the highest level of fire protection. Type V, on the other hand, is the least stringent.
Each type of construction is further described as “A” or “B.” Suffice it to say that a type B designation is basic and type A is enhanced. For the purpose of this overview, we’ll start by describing the least stringent construction Type V, and work our way up to Type I.
Walls and framing can be built out of any materials allowed by code with Type V construction, typically wood. A Type V-B construction, the most basic, does not require a fire resistance rating for any of the building elements. The building elements are the primary structural frame, bearing walls, non-bearing walls, floor construction, and roof construction. It is a budget-friendly option but, because the structure has inherently lower fire ratings, it comes with use limitations and may need bigger setbacks or barriers to protect adjacent properties.
The type of activities that takes place within a structure can help determine whether Type V wood-frame construction is an option. Single-family residential homes are the most common application. Some commercial buildings such as restaurants, office buildings, or even a small theater might be wood-framed as well.
But Type V construction buildings are always smaller than a building of the same use built to a more stringent type of construction. And, in any construction type, even if the building use doesn’t require sprinklers, the addition of sprinklers is always recommended to enhance safety. Sprinklered buildings of the same construction type and use as a non-sprinklered building can be larger.
As the fire resistance of the building materials increases, you have the ability to construct larger facilities. A hotel made of Type V construction might only be 7,000 square feet, for example, whereas a Type IV heavy timber hotel could be 20,000 square feet.
With Type IV construction, the interior walls and framing can be heavy timber while the exterior walls can be made of non-rated materials. Timber framing differs from traditional wood-frame construction in that the beams and girders are thicker and stronger, often made of laminated wood. The heavier timber effectively creates resistance to fire. While the exterior of an 8-inch beam may become charred, it will burn more slowly, allowing occupants more time to escape prior to collapse and giving sprinkler systems, if present, a chance to put out the fire.
Exterior walls of Type III construction are built with brick, masonry, concrete block, precast panels, or other non-combustible materials. However, interior structures and the roof can be wood-framed. In essence, the walls of the building have a good fire-resistance rating, but the interior and roof trusses may be more prone to collapsing if they catch fire. The goals of Type III construction are to contain any fire within the exterior walls of the building and mitigate the fire’s spread to adjacent buildings.
A smaller Type III building allows occupants time to escape before a fire gets out of control. The risk of roofs collapsing may be minimized by designing a structure with higher ceilings that essentially put flames “out of reach.”
Many commercial retail buildings like strip malls and big-box stores use Type II construction. All building materials, including interior walls, framing, floors, roofing, and exteriors, are made of non-combustible materials such as metal and concrete block. Size requirements are similar to those for Type III and, even though the building materials are categorized as non-combustible, they provide less fire resistance than Type I, and a spreading fire would likely cause more damage.
Type I buildings are the Cadillac of construction types and are made of high-quality non-combustible materials, such as poured concrete and steel framing that’s protected or insulated from fire, and are rated to withstand fires for two to three hours. This rating provides the highest levels of safety.
High-rises and many large and/or other multi-story buildings are categorized as Type I construction. As mentioned previously, building types are sometimes categorized further as A or B. A Type I–B building (the “basic” Type I construction) might be 160 feet high with 12–16 stories. A Type I–A building (the “enhanced” Type I construction) adds even more layers of protection and is required for buildings like skyscrapers where even the height is unlimited (in theory). With a few exceptions, Type I construction doesn’t have size limitations.
The many nuances of a building’s use and size requirements can complicate things and create confusion over which type of construction is best suited. Hospitals or jails where occupants are confined and unable to exit on their own may require more stringent types of construction even as single-story buildings.
Of course, budgets play a big role as well. Your construction manager can help you assess your needs and make building recommendations early on, helping you determine an accurate budget and, most importantly, ensure the safety of others. Contact the building experts at The Samuels Group today to discuss your project, and check out our guide below containing additional questions to bring up during the conversation.
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