From 2009
406.1 Private garages and carports.
406.1.1 Classification. Buildings or parts of buildings classified as Group U occupancies because of the use or character of the occupancy shall not exceed 1,000 square feet (93 m2) in area or one story in height except as provided in Section 406.1.2. Any building or portion thereof that exceeds the limitations specified in this section shall be classified in the occupancy group other than Group U that it most nearly resembles.
Whereas private garages are smaller than parking garages by definition, the impact of the fuel load represented by the vehicle is somewhat higher. Such garages are frequently attached to residential-type occupancies, with the potential for fire exposure to the residential area and the occupants therein. The code does not specifically prohibit the servicing of vehicles in private garages, since it would be impractical to enforce. For example, the occupant of a residential dwelling unit will occasionally work on a vehicle in an attached private garage. For this reason, there are special provisions for private garages.
Private garages and carports are usually considered accessory to the building they serve. Section 312 classifies these utility and miscellaneous uses as Group U. The code limits these structures to 1,000 square feet (93 m2) in area and one story in height. Those limitations correspond to a fuel load associated with the passenger motor vehicles that is matched by the specified separation requirements. Separation and construction details for private garages attached to dwelling units are provided in Section 406.1.4. This separation includes the 1/2-inch (12.7 mm) regular or 5/8-inch (15.9 mm) Type X gypsum board applied to the garage side (see Section 406.1.4 for further details).
Any garage that exceeds the height and area limits of Section 406.1.1 or the area increase of Section 406.1.2 must be reclassified. Once the specified height and area limits have been exceeded, the garage must be classified for the increased hazards. This results in the garage being classified as Group S-2, and the provisions of Sections 406.2 and 406.3 or 406.4 must now be met.
406.1.2 Area increase. Group U occupancies used for the storage of private or pleasure-type motor vehicles where no repair work is completed or fuel is dispensed are permitted to be 3,000 square feet (279 m2) when the following provisions are met:
1. For a mixed occupancy building, the exterior wall and opening protection for the Group U portion of the building shall be as required for the major occupancy of the building. For such a mixed occupancy building, the allowable floor area of the building shall be as permitted for the major occupancy contained therein.
2. For a building containing only a Group U occupancy, the exterior wall shall not be required to have a fire-resistance rating and the area of openings shall not be limited when the fire separation distance is 5 feet (1524 mm) or more.
More than one 3,000-square-foot (279 m2) Group U occupancy shall be permitted to be in the same building, provided each 3,000-square-foot (279 m2) area is separated by fire walls complying with Section 706.
The area of a private garage can be increased to 3,000 square feet (279 m2) when all of the conditions of this section are met. If the garage will only be used for the parking and storage of private or pleasure-type motor vehicles, then the area increase may be used. Care must be taken such that no repair work or fuel dispensing is done within these areas. The limitations to private- or pleasure-type motor vehicles prevent commercial motor vehicles and their increased hazards from being located in this larger private garage.
As part of the increased area provisions for private garages, the exterior walls and any openings therein must be properly protected. If the garage is part of another occupancy, then the exterior wall ratings for that occupancy apply to the garage. For example, an automobile insurance office may have several parking bays attached to it. These bays will be used to bring damaged cars in for the purposes of evaluating the damage and estimating the cost of repairs for the vehicle owner. The insurance office spaces are usually classified as Group B. In this case, the allowable building area is based on the Group B occupancy, the garage area is limited to 3,000 square feet (279 m2) and the exterior walls and openings in the garages are rated as part of the Group B occupancy.
For other applications, where the buildings only will be used to park vehicles, the building is classified as Group U. The exterior walls and openings therein are not required to be rated or limited if the fire separation distance is 5 feet (1524 mm) or more.
Additional private garages can be added to a Group U building, but they must be separated with fire walls. The 3,000-square-foot (279 m2) limit is a maximum. To reduce the risk of a fire from involving other adjacent garage spaces, fire walls are required to compartmentalize and further isolate the hazards. If the garages are located below another occupancy, such as Group R-2 apartments, the fire walls will be required to continue through to the roof of the residential portion of the building.
406.1.3 Garages and carports. Carports shall be open on at least two sides. Carport floor surfaces shall be of approved noncombustible material. Carports not open on at least two sides shall be considered a garage and shall comply with the provisions of this section for garages.
Exception: Asphalt surfaces shall be permitted at ground level in carports.
The area of floor used for parking of automobiles or other vehicles shall be sloped to facilitate the movement of liquids to a drain or toward the main vehicle entry doorway.
Carports are covered structures, either free-standing or attached to the side of a building, for the purposes of providing shelter for motor vehicles. Carports must be open on at least two sides. This allows a fire condition to vent quickly to the outside. This further prevents a fire from going undetected and usually limits the amount of other incidental storage that may be included in a fully enclosed garage. Attached carports that are not open on at least two sides are considered a garage and must then be separated from the residence or other occupancy (see Section 406.1.4 for further details).
The use of a combustible floor finish that could absorb flammable and combustible liquids commonly used and stored within garages and carports presents a potential safety hazard to the occupants of an attached building. The floors of private garages must be sloped towards the main vehicle doors. Although not specified, the floor must be positively sloped at some rate, such as 1 in 48 (2-percent slope), to prevent the accumulation of any spilled flammable and combustible liquids and their vapors. This minimizes the risk of the vapors building up to a point where a fir condition could result.
