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# IBC Chapter 6 - Building Types

> Understanding Building Typologies

*Written by Patricia Causey · Updated March 27, 2026*

The IBC categorizes buildings into five different types based on their fire resistant properties. Each of these types also have subtypes of A and B, Type IV has additional subcategories of C and HT. Type V is the least fire resistant while Type I is the most fire resistant. The subtype A indicates more fire resistant materials than subtype B. Please refer to the [IBC Chapter 6](https://codes.iccsafe.org/content/IBC2024V2.0/chapter-6-types-of-construction#IBC2024V2.0_Ch06_Sec601_Tbl601) for your code studies and research.

### **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

### **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

### **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

### **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

### **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