Type 2 construction, also called non-combustible construction, is one of five building construction classifications defined by the International Building Code (IBC). It requires that all structural materials, including walls, floors, and the roof, be made from non-combustible materials like steel, concrete, or masonry. What separates Type 2 from the highest-rated Type 1 is the level of fire resistance those materials must provide. Type 2 buildings use similar non-combustible materials but with lower fire-resistance ratings, which means they cost less to build while still offering significant protection against fire spread.
How Type 2 Construction Works
The defining feature of Type 2 construction is that nothing in the structural system burns. Steel framing, concrete block walls, metal decking, and similar materials make up the building’s bones. Wood and other combustible materials are generally limited to interior finishes, furnishings, and certain non-structural components.
This matters because in a fire, the structural frame of a Type 2 building will not add fuel to the blaze. However, unprotected steel can lose strength at high temperatures, which is why the IBC divides Type 2 into two subcategories based on how much fire-resistant protection those steel and concrete elements must carry.
Type II-A vs. Type II-B
The two subcategories differ primarily in their required fire-resistance ratings, measured in hours. A fire-resistance rating indicates how long a structural element can withstand fire exposure before it fails.
- Type II-A (Protected Non-Combustible): Exterior walls, the structural frame, and floor and roof assemblies must all carry at least a one-hour fire-resistance rating. This is achieved by applying fireproofing materials to steel members, such as spray-on coatings, intumescent paint, or encasing steel in concrete or gypsum board. The added protection gives occupants and firefighters more time during a fire.
- Type II-B (Unprotected Non-Combustible): The structural materials are still non-combustible, but they carry little to no required fire-resistance rating. Exposed steel beams and columns are common. This makes Type II-B cheaper and faster to build, but the steel frame is more vulnerable to weakening or collapse during a prolonged fire.
These ratings from IBC Table 601 are minimums. Other code provisions can require higher ratings depending on the building’s occupancy type, height, or proximity to other structures.
Where You See Type 2 Buildings
Type 2 construction is extremely common in commercial development. Type II-B, the unprotected version, is the most widely used non-combustible construction type for commercial buildings. Think of single-story retail stores, warehouses, auto repair shops, and strip malls with exposed steel framing and metal roofing. These buildings are relatively inexpensive to put up and work well for occupancies where height and density are modest.
Type II-A shows up in buildings where codes demand more protection due to the number of occupants or stories. Newer school buildings are a common example. Mid-rise office buildings, medical clinics, and larger retail structures also frequently use Type II-A construction to meet code requirements while keeping costs below what a fully fire-resistive Type 1 building would require.
How Type 2 Compares to Other Construction Types
The IBC defines five construction types, numbered I through V, with Type I offering the most fire protection and Type V the least. Type 2 sits just below the top tier.
Type 1 (fire-resistive) uses the same non-combustible materials as Type 2 but requires much higher fire-resistance ratings, often two to three hours for structural frames. High-rises, hospitals, and large public buildings typically require Type 1 construction. The additional fireproofing and heavier structural members make Type 1 significantly more expensive.
Types III, IV, and V all permit combustible materials (primarily wood) in varying degrees. Type III requires non-combustible exterior walls but allows wood framing inside. Type IV is heavy timber construction. Type V permits combustible materials throughout, including wood-framed exterior walls. This is the standard for most residential homes and small apartment buildings.
Type 2 occupies a practical middle ground: fully non-combustible like Type 1, but without the extensive (and expensive) fireproofing requirements. For developers, this translates to lower material and labor costs while still building something far more fire-resistant than wood-framed construction.
Height and Area Limits
The IBC restricts how tall a building can be and how large each floor can be based on its construction type. Because Type 2 has lower fire-resistance ratings than Type 1, it comes with tighter limits on both height and floor area.
The exact limits depend on the building’s occupancy classification (office, retail, assembly, residential, etc.) and whether automatic sprinklers are installed. Adding a sprinkler system allows significant increases to both permitted height and floor area under the code. For many commercial projects, the combination of Type II-B construction with a sprinkler system hits a sweet spot of cost efficiency and code compliance, allowing a reasonably sized building without the expense of higher-rated construction.
Type II-A, with its one-hour ratings, is permitted to be taller and larger than Type II-B for the same occupancy type. Choosing between the two subcategories often comes down to whether the project’s size and use can fit within II-B’s limits or whether II-A’s expanded allowances are needed.
Cost Considerations
Type 2 construction generally costs more than wood-framed Type V buildings but less than Type 1. Steel and concrete are more expensive than lumber, and the labor to erect steel framing requires specialized crews. However, the construction industry has developed increasingly efficient methods for steel and metal building systems, which has helped narrow the cost gap in many markets.
The choice between II-A and II-B has direct cost implications. Applying fireproofing to every structural member in a II-A building adds material, labor, and inspection requirements. For a project that can legally be built as II-B, skipping that fireproofing layer saves both money and construction time.
Insurance is another factor. Buildings made entirely of non-combustible materials generally carry lower fire insurance premiums than wood-framed structures. The exact savings depend on the insurer, the building’s use, its location, and whether sprinklers are installed, but the non-combustible classification is consistently favorable in underwriting.
Fire Behavior in Type 2 Buildings
While the structure itself will not burn, the contents of any building (furniture, inventory, finishes) absolutely will. In a Type II-B building with unprotected steel, a contents fire that burns long enough can heat steel columns and beams to the point where they lose structural integrity. Steel begins to lose significant strength at around 1,000°F, and building fires can exceed that temperature within minutes.
This is why Type II-A’s one-hour rating matters. The fireproofing layer insulates the steel, buying critical time. It also explains why sprinkler systems are so important in Type 2 buildings. A sprinkler system controls or extinguishes a fire before it can generate enough sustained heat to threaten the structure, effectively compensating for lower fire-resistance ratings.