IBC Chapter 6 - Building Types

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Type I - Fire-Resistive Construction

• Type IA:
  • Fire Ratings: Structural frame (3 hours), bearing walls exterior (3 hours), bearing walls interior (3 hours), floor construction (2 hours), roof construction (1½ hours)
    • Materials Examples: Concrete-encased structural steel, reinforced concrete columns and beams, concrete floor slabs, masonry or concrete bearing walls
    • Building Example: High-rise office towers, hospitals over 75 feet, skyscrapers
• Type IB:
  • Fire Ratings: Structural frame (2 hours), bearing walls exterior (2 hours), bearing walls interior (2 hours), floor construction (2 hours), roof construction (1 hour)
    • Materials Examples: Spray-applied fireproofing on steel, concrete columns, precast concrete, steel with gypsum encasement, concrete masonry units (CMU)
    • Building Example: Mid-rise hotels, parking garages, larger hospitals, university classroom building

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Type II - Noncombustible Construction

• Type IIA:
  • Fire Ratings: Structural frame (1 hour), bearing walls exterior (1 hour), bearing walls interior (1 hour), floor construction (1 hour), roof construction (1 hour)
    • Materials Examples: Protected steel framing, metal deck with concrete topping, CMU walls, fire-rated gypsum assemblies on steel studs
    • Building Example: Low-rise office buildings, schools, smaller shopping centers, medical offices
• Type IIB:
  • Fire Ratings: 0 hours for all elements (unrated but noncombustible)
    • Materials Examples: Unprotected steel framing, steel bar joists, metal roof deck, exposed steel beams and columns, aluminum framing, CMU or metal panel exterior walls
    • Building Example: Warehouses, mini-storage facilities, big-box retail stores, light industrial buildings, aircraft hangars

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Type III - Exterior Protected Construction

• Type IIIA:
  • Fire Ratings: Structural frame (1 hour), bearing walls exterior (2 hours), bearing walls interior (1 hour), floor construction (1 hour), roof construction (1 hour)
    • Materials Examples: Brick or CMU exterior walls, wood or protected steel interior framing, fire-rated wood floor assemblies with gypsum protection, Type X gypsum board on interior walls
    • Building Example: Mixed-use buildings with retail below and apartments above, urban row houses, small downtown commercial buildings
• Type IIIB:
  • Fire Ratings: Structural frame (0 hours), bearing walls exterior (2 hours), bearing walls interior (0 hours), floor construction (0 hours), roof construction (0 hours)
    • Materials Examples: Brick or concrete block exterior, unprotected wood framing interior, dimensional lumber joists and rafters, plywood sheathing
    • Building Example: Strip malls, single-story retail with masonry facade, small restaurants, auto repair shops

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Type IV - Mass Timber Construction

• Type IV-A:
  • Fire Ratings: Structural frame (3 hours), bearing walls exterior (2 hours), bearing walls interior (2 hours), floor construction (2 hours), roof construction (1½ hours)
    • Materials Examples: Cross-laminated timber (CLT) panels with additional fire protection layers, glued-laminated timber (glulam) beams with encapsulation, nail-laminated timber (NLT), fire-retardant-treated wood, noncombustible exterior walls
    • Building Example: Tall mass timber residential towers (up to 18 stories), large mass timber office buildings, innovative high-rise wood construction
• Type IV-B:
  • Fire Ratings: Structural frame (2 hours), bearing walls exterior (2 hours), bearing walls interior (2 hours), floor construction (2 hours), roof construction (1 hour)
    • Materials Examples: Exposed or minimally protected CLT floors and roofs, glulam columns and beams, dowel-laminated timber (DLT), mass plywood panels (MPP), may use some gypsum protection
    • Building Example: Mid-rise mass timber apartments (6-12 stories), mass timber university buildings, modern timber office buildings
• Type IV-C:
  • Fire Ratings: Structural frame (2 hours), bearing walls exterior (2 hours), bearing walls interior (2 hours), floor construction (2 hours), roof construction (1 hour - but with less protection than IV-B)
    • Materials Examples: Exposed mass timber elements meeting minimum dimensional requirements, CLT with minimal char layer, large glulam members, structural composite lumber (SCL), noncombustible or fire-rated exterior walls
    • Building Example: Low-rise mass timber buildings (3-5 stories), mass timber mixed-use structures, timber-frame apartment buildings
• Type IV-HT (Heavy Timber):
  • Fire Ratings: Bearing walls exterior (2 hours), other elements meet heavy timber dimensional requirements
    • Materials Examples: Large sawn timbers (minimum 8” × 8” columns, 6” × 10” beams, 2” tongue-and-groove decking), timber trusses with minimum 8” members, traditional mill construction
    • Building Example: Historic mill buildings, timber-frame churches, post-and-beam restaurants, converted warehouses, craft breweries

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Type V - Wood Frame Construction

• Type VA:
  • Fire Ratings: Structural frame (1 hour), bearing walls exterior (1 hour), bearing walls interior (1 hour), floor construction (1 hour), roof construction (1 hour)
    • Materials Examples: 2×4 or 2×6 wood stud walls with Type X gypsum board, dimensional lumber floor joists with gypsum ceiling below, engineered lumber (I-joists, LVL), wood or vinyl siding over fire-rated sheathing
    • Building Example: 3-5 story apartment buildings (“5-over-1” podium construction), townhomes, small hotels, wood-frame condominiums
• Type VB:
  • Fire Ratings: 0 hours for all elements (unprotected wood frame)
    • Materials Examples: Standard 2× dimensional lumber framing, plywood or OSB sheathing, wood trusses, unprotected wood studs, standard ½” drywall (non-rated), any exterior cladding
    • Building Example: Single-family homes, detached garages, small wood-frame duplexes, garden sheds, small residential accessory structures