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International Building Code (IBC) Categories
The five IBC categories identify the level of fire protection provided by five types of construction. The construction type chosen for a structure determines important parameters such as the building’s:
- Permissible uses
- Maximum occupancy
- Square footage
- Proximity to other structures
- Placement of windows and exits
- Fire resistance
- Need for sprinklers
Type I is the most stringent and Type V is the least stringent in terms of fire resistance. Additionally, each category is further designated as “A” or “B” for basic or enhanced protection.
Construction Types & Building Codes
Type I Construction
Type I buildings are made of fire resistive and non-combustible materials (concrete and steel) and are rated as being able to resist fire for 2-3 hours. In general, high-rise and high-occupancy buildings are construction type I-A.
- Type I-A provides enhanced protection against fire—3 hours for exterior walls and structural frame, 2 hours for floor/ceiling assemblies, and 1.5 hours for the roof.
- Type I-B, typically used for mid-rise office buildings, provides slightly less fire resistance—2 hours for exterior walls, structural frame, and ceiling/floor separation, and 1 hour for ceiling/roof assemblies.
Type II Construction
Type II construction is non-combustible. This type of construction often is used for commercial retail buildings. Like Type I buildings, Type II structures are made of concrete and steel.
- Type II-A Protected non-combustible construction provides 1-hour resistance against fire for exterior walls, structural frames, and floors, ceilings, and roofs.
- Type II-B buildings are made of non-combustible materials that provide no fire resistance. This is the most common construction type used in commercial buildings.
Type III Construction
Type III construction has exterior walls made of non-combustible materials such as brick, concrete block, masonry, precast concrete panels, or wood treated with a fire retardant. Roofs and interior walls may be wood-framed and consequently may be more likely to collapse in a fire. Type III is commonly referred to as “ordinary construction.”
- Type III-A protected combustible construction provides 2-hour fire resistance for exterior walls and 1-hour protection for the structural frame, floors, and ceilings.
- Type III-B unprotected combustible construction provides 2-hour fire resistance for exterior walls, but the structural frame, floors, ceilings, and roofs are not fire-resistant. Type III-B most often is found in older construction.
Type IV Construction
In Type IV construction, exterior walls may be made of non-rated materials, while framing and interior walls are made of heavy timber. To qualify as “heavy timber,” beams must have a minimum nominal thickness of 8 inches. Heavy timber often is laminated wood, which provides some fire resistance. It will burn, but more slowly than traditional wood-frame construction, which provides some time for occupants to escape and for sprinklers to kick in and suppress the fire.
Type IV construction is not designated as A or B. Exterior walls provide 2-hour fire resistance.
Type V Construction
Type V is wood frame construction. Structural elements and both exterior and interior walls can be made of any material allowed by the local building code. Type V construction is most commonly used for single-family homes.
- Type V-A, protected wood frame construction, has no exposed wood and is often used in the construction of multi-family homes. It provides 1-hour fire resistance for exterior walls, structural frame, floors, ceilings, and roof.
- Type V-B, unprotected wood frame construction, often has exposed wood and provides no fire resistance.
Significance to Contractors
Every jurisdiction has its own building code, a set of regulations modeled after the Internal Business Code, which is far more extensive and detailed than this description of construction types. And every jurisdiction requires a building permit for any construction project that could impact the safety and wellbeing of a structure’s occupants. Inspections are performed at certain points to ensure that work is done in accordance with the applicable regulations.
Building Bonding Capacity
Building a track record of successful projects and regulatory compliance is essential for establishing the bonding capacity to support a thriving construction business. Surety bond underwriters rely heavily on a construction bond applicant’s industry experience, financial strength, and stability to approve a bond and set the annual bond premium rate.
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