11.3 South Carolina Building Code: Occupancy & Construction Types

South Carolina Building Code Regulatory Framework

Commercial construction throughout South Carolina is governed by the South Carolina Building Code. It is based on the International Building Code (IBC) published by the International Code Council (ICC), with South Carolina modifications. South Carolina's 2021-edition codes took effect January 1, 2023, and the current PSI Limited Building bulletin lists the 2021 IBC with SC modifications or the 2018 or 2021 South Carolina Building Code as references. The statutory adoption of building codes is administered by the South Carolina Building Codes Council, operating under the administrative authority of the Department of Labor, Licensing and Regulation (SC LLR) in Columbia.

Local Administration and Enforcement

While the Building Codes Council establishes statewide mandatory codes, day-to-day administration and enforcement are performed locally by municipal and county building departments. The Local Building Official is vested with statutory authority to:

• Review and approve construction plans, structural calculations, and engineering specifications prior to permit issuance.
• Issue commercial building permits and verify contractor licensing credentials under Title 40 Chapter 11.
• Conduct mandatory field inspections: foundation and footings, under-slab utilities, rough framing, rough mechanical/electrical/plumbing (MEP), insulation/air barrier, and final life-safety inspections.
• Issue Stop Work Orders for non-compliant or hazardous construction activities.
• Issue the Certificate of Occupancy (CO), without which a newly constructed or renovated commercial building cannot be lawfully occupied or placed into service.

Building Occupancy Classifications (IBC Chapter 3)

Every commercial building or tenant space must be classified into one or more of the 10 primary Occupancy Groups defined under IBC Chapter 3. Occupancy classification is the critical starting point for determining allowable building height, maximum floor area, mandatory fire protection systems, and means of egress sizing.

The Ten Major Occupancy Classifications

1. Group A (Assembly): Buildings or spaces utilized for the gathering of 50 or more persons for civic, social, religious, recreation, food/drink consumption, or awaiting transportation:
   • A-1: Theaters with fixed seating for the viewing of motion pictures or performing arts.
   • A-2: Food and drink consumption establishments, including restaurants, bars, taverns, cafeterias, and nightclubs.
   • A-3: Spaces utilized for worship, recreation, or amusement not classified elsewhere, including churches, synagogues, community halls, libraries, art galleries, and gymnasiums without spectator seating.
   • A-4: Indoor sporting arenas, skating rinks, and swimming pools with spectator seating.
   • A-5: Outdoor sporting arenas, stadiums, and amusement park structures.
   • The 50-Person Assembly Exception: An assembly space with an occupant load of fewer than 50 persons is classified as Group B (Business) or as an accessory occupancy.
2. Group B (Business): Spaces utilized for office, professional, civic, or service transactions, including commercial banks, corporate offices, civic government administration, medical and dental clinics, and ambulatory outpatient clinics.
3. Group E (Educational): Buildings utilized by six or more persons at any one time for educational purposes through the 12th grade. Also includes daycare facilities for more than five children older than 2.5 years of age.
4. Group F (Factory and Industrial): Structures utilized for assembling, disassembling, fabricating, finishing, manufacturing, or processing operations:
   • F-1 (Moderate-Hazard): Commercial manufacturing involving combustible materials (woodworking, commercial bakeries, textile mills, furniture fabrication).
   • F-2 (Low-Hazard): Fabrication of non-combustible materials (metal fabrication, ceramic foundries, ice manufacturing, glass production).
5. Group H (High-Hazard): Structures utilized for manufacturing, processing, generation, or storage of materials that constitute a high physical hazard (explosion, deflagration) or health hazard (toxic gas) in quantities exceeding the Maximum Allowable Quantities (MAQ) per control area (H-1 explosives, H-2 flammable vapors/liquids, H-3 combustible dusts, H-4 toxic chemicals, H-5 semiconductor fabrication).
6. Group I (Institutional): Structures in which people are cared for or reside in a supervised environment having physical or medical limitations, or where people are detained for correctional purposes:
   • I-1: Residential board and care facilities with more than 16 persons on a 24-hour basis (assisted living facilities, group homes).
   • I-2: Medical, surgical, psychiatric, or nursing care on a 24-hour basis for non-ambulatory patients (hospitals, nursing homes, psychiatric facilities).
   • I-3: Incarceration or detention facilities where occupants are restrained (prisons, jails, reformatories, detention centers).
   • I-4: Daycare facilities providing custodial care for more than 5 persons of any age for less than 24 hours (adult daycares, infant child-care centers for children under 2.5 years).
7. Group M (Mercantile): Buildings used for the display and retail sale of merchandise, with accessible customer stocks, including department stores, supermarkets, retail pharmacies, and wholesale retail clubs.
8. Group R (Residential): Structures providing sleeping accommodations not classified as Group I:
   • R-1: Residential occupancies where occupants are primarily transient in nature (stays less than 30 days), including hotels, motels, and commercial boarding houses.
   • R-2: Residential occupancies containing more than two permanent dwelling units, including apartment buildings, residential condominiums, non-transient boarding houses, and college dormitories.
   • R-3: Permanent 1- and 2-family dwellings, or small care facilities (commercial IBC applies to triplexes and above; detached 1-2 family homes fall under the IRC).
   • R-4: Small residential care/assisted living facilities housing between 6 and 16 occupants.
9. Group S (Storage): Structures used for storage not classified as Group H. S-1 Moderate-Hazard (combustible goods, cardboard, lumber storage, vehicle repair garages); S-2 Low-Hazard (non-combustible products, enclosed and open parking garages).
10. Group U (Utility and Miscellaneous): Agricultural barns, carports, detached private garages, sheds, retaining walls, and communication towers.

Mixed Occupancy Provisions (IBC Section 508)

Commercial projects frequently combine distinct occupancy groups (e.g., ground-floor Group M retail beneath four stories of Group R-2 apartments). The code provides three design approaches:

• Accessory Occupancies (IBC 508.2): Minor occupancy areas that do not exceed 10% of the building area of the story in which they are located. Accessory spaces do not require rated fire separations from the primary occupancy (except for Group H).
• Non-Separated Occupancies (IBC 508.3): No fire-rated partitions are required between occupancies. However, the most restrictive height, allowable area, and construction type provisions of all occupancies present apply to the entire building.
• Separated Occupancies (IBC 508.4): Occupancies are physically separated by rated fire barriers or horizontal assemblies per IBC Table 508.4 (typically 1- to 3-hour fire ratings). Each separated portion is evaluated based on its own specific occupancy rules.

Types of Construction (IBC Chapter 6)

Every commercial building is categorized into one of five basic Types of Construction (Types I, II, III, IV, and V) under IBC Chapter 6, based on the combustibility and fire-resistance ratings of its structural components:

• Types I and II: Structural elements (columns, beams, floors, roofs, exterior walls) must be constructed of non-combustible materials (structural steel, reinforced concrete, and concrete masonry units).
• Type III: Exterior walls must be non-combustible (masonry or concrete), while interior structural framing, floors, and roofs may be constructed of any material permitted by code, including combustible wood framing or light-gauge cold-formed steel.
• Type IV: Heavy Timber (HT). Exterior walls are non-combustible, and interior framing members consist of solid-sawn or engineered mass timber without concealed spaces.
• Type V: Any materials permitted by code may be used, including standard dimensional wood framing, wood trusses, or light-gauge steel.

Sub-Classifications: Protected (A) vs. Unprotected (B)

Types I, II, III, and V are further subdivided into 'A' (Protected) and 'B' (Unprotected) categories. The designation 'A' indicates that structural steel, framing, and deck assemblies are protected with fire-resistive materials (such as spray-applied fireproofing, gypsum board enclosures, or concrete encasement) to achieve specific hourly ratings:

+------------------------------------------------------------------------------------------------+
|                 IBC CHAPTER 6 STRUCTURAL FIRE-RESISTANCE RATINGS MATRIX                        |
+--------------------+----------------+----------------+----------------+------------------------+
| CONSTRUCTION TYPE  | PRIMARY FRAME  | EXTERIOR WALLS | INTERIOR FLOORS| ROOF CONSTRUCTION      |
+--------------------+----------------+----------------+----------------+------------------------+
| Type I-A           | 3 Hours        | 3 Hours        | 2 Hours        | 1.5 Hours              |
| Type I-B           | 2 Hours        | 2 Hours        | 2 Hours        | 1 Hour                 |
| Type II-A          | 1 Hour         | 1 Hour         | 1 Hour         | 1 Hour                 |
| Type II-B          | 0 Hours (Unpr) | 0 Hours        | 0 Hours (Unpr) | 0 Hours (Unprotected)  |
| Type III-A         | 1 Hour         | 2 Hours (Nonc) | 1 Hour         | 1 Hour                 |
| Type III-B         | 0 Hours        | 2 Hours (Nonc) | 0 Hours        | 0 Hours                |
| Type IV-HT         | Heavy Timber   | 2 Hours (Nonc) | Heavy Timber   | Heavy Timber           |
| Type V-A           | 1 Hour         | 1 Hour         | 1 Hour         | 1 Hour                 |
| Type V-B           | 0 Hours (Unpr) | 0 Hours (Unpr) | 0 Hours (Unpr) | 0 Hours (Unprotected)  |
+--------------------+----------------+----------------+----------------+------------------------+

Practical Field Distinctions

• Type I-A / I-B: Utilized for high-rise buildings, major hospitals, and regional shopping malls. Structural steel columns and beams require thick spray-applied fire-resistive material (SFRM) or concrete encasement.
• Type II-B (Unprotected Commercial Steel): One of the most prevalent commercial types in South Carolina. Consists of structural steel columns, open-web steel roof joists, and metal decking with zero fireproofing required. Common for big-box retail stores, strip shopping centers, and industrial warehouses.
• Type III-A / III-B (Traditional Commercial): Often termed "ordinary construction." Masonry or tilt-up concrete exterior perimeter walls (2-hour rating) enclosing interior wood post-and-beam or light-frame floors and roofs. Prevalent in suburban multi-family apartments and historic commercial downtowns.
• Type V-A / V-B (Wood Frame): Standard platform wood framing. Type V-A requires a 1-hour fire-rated membrane (5/8-inch Type X gypsum board) on all walls, ceilings, and structural members. Type V-B has 0-hour ratings, used for small single-story commercial offices and local convenience retail.

Building Height & Allowable Area Calculations (IBC Chapter 5)

The allowable height (in feet and stories) and maximum floor area per story are strictly governed by IBC Chapter 5, determined as a function of the building's Occupancy Group and Type of Construction.

The Base Allowable Area (At)

IBC Table 506.2 provides the base tabular allowable floor area (At) per story for single-occupancy non-sprinklered buildings. For instance, a Group B office building constructed as Type II-B has a base tabular area of 23,000 sq ft per story, whereas the same office constructed as Type II-A (1-hour protected) has a base tabular area of 37,500 sq ft.

Allowable Area Increases: Sprinklers & Perimeter Frontage

To encourage superior life-safety design and provide firefighter access, the building code grants substantial allowable area increases for automatic fire sprinklers and perimeter open space:

Aa = At + (At x If) + (At x Is)

Where:

• Aa = Total modified allowable area per story.
• At = Base tabular allowable area per story from Table 506.2.
• If = Frontage area increase percentage.
• Is = Automatic fire sprinkler increase percentage.

1. Automatic Fire Sprinkler Increase (Is)

Under IBC Section 506.3, equipping a commercial building throughout with an approved NFPA 13 automatic fire sprinkler system provides massive area increases:

• Multi-Story Buildings: 200% increase (Is = 2.00), effectively tripling the base area (3 x At).
• Single-Story Buildings: 300% increase (Is = 3.00), effectively quadrupling the base area (4 x At).
• Height Increase: An approved NFPA 13 sprinkler system also grants an allowable building height increase of one additional story and 20 additional vertical feet above base table limits for most occupancies.
• Restrictions: Sprinkler area increases are prohibited where sprinklers are already utilized to substitute for 1-hour fire-resistance-rated construction, and in Group H-1 explosive occupancies.

2. Perimeter Open Space Frontage Increase (If)

Under IBC Section 506.3.3, when a commercial building has more than 25% of its total perimeter fronting on a public way or open space having a minimum clear width of 20 feet, the building earns an area increase to reward unobstructed fire department ladder and pumper access:

If = [(F / P) - 0.25] x (W / 30)

Where:

• F = Building perimeter fronting on a public way or open space not less than 20 feet wide.
• P = Total building perimeter.
• W = Minimum clear width of the open space (measured perpendicular to building), minimum 20 feet, with a statutory maximum cap of 30 feet (W / 30 <= 1.0).
• Maximum Cap: Under IBC Section 506.3.3, the maximum allowable frontage increase (If) is capped at 75% (If = 0.75).

Passive Fire Resistance & Compartmentation

Passive fire protection relies on compartmentalizing buildings with rated construction assemblies to prevent the spread of fire, radiant heat, toxic smoke, and hot gases. IBC Chapter 7 establishes distinct classifications of fire-rated assemblies:

Fire Walls vs. Fire Barriers vs. Fire Partitions

Contractors must understand the critical structural and regulatory differences among rated assemblies:

The 30-Inch Fire Wall Parapet Requirement

Under IBC Section 706.6, a fire wall must terminate in a parapet extending at least 30 inches vertically above the point where the roof surfaces meet the wall. This prevents flames and radiant heat from leaping across combustible roof assemblies from one side of the fire wall to the other. The parapet must have the same fire-resistance rating as the fire wall.

• Exceptions to Parapet: A parapet is not required if the roof consists of non-combustible materials (such as concrete or steel deck with Class A roofing) and the roof surface within 4 feet of the wall has no openings.

Opening Protectives & Fire Damper Operation

Openings in fire-rated walls compromise compartmentation unless protected by rated assemblies:

• Fire Door Assemblies: Doors installed in fire walls and barriers must bear certified laboratory testing labels (UL or Warnock-Hersey). Doors in 3-hour fire walls require a 3-hour rated door; doors in 2-hour exit stair enclosures require a 1.5-hour (90-minute) door; doors in 1-hour corridor partitions require a 20-minute door. All fire doors must be self-closing or automatic-closing upon smoke detection.
• Fire Dampers in HVAC Ducts: Where heating, ventilation, or air conditioning ducts penetrate fire walls, barriers, or partitions, approved fire dampers must be installed within the duct inside the plane of the wall. Fire dampers utilize a fusible link (typically melting at 165°F) or an electric motorized actuator that triggers spring-loaded blades to snap shut, blocking flames.
• Through-Penetration Firestops (ASTM E814 / UL 1479): When pipes, conduits, or cables penetrate fire-rated assemblies, the annular space must be sealed with tested firestop systems:
  • F-Rating (Flame): The time period (in hours) that the firestop system prevents flame penetration through the assembly to the unexposed side.
  • T-Rating (Temperature): The time period (in hours) that the firestop limits the temperature rise on the unexposed side to no more than 325°F above initial ambient temperature, preventing spontaneous combustion of combustible materials touching the penetrating pipe.