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Before the invention of the automobile, garages were represented by carriage houses (coach houses or remises). These early structures, mostly glorified barns detached from the home, had no fire danger due to the combination of stored Hay and lanterns. Today’s garages are attached to nearly 97% of homes.
Modern garages have evolved to the point where only 25% of homeowners can park their vehicles in them. Half of the homeowners can fit one car into their garage, while the other quarter are able to park multiple cars there. Many people use their garage to store personal items. There are many other uses for your garage space, including rehearsal studios and hobby shops as well as budding dot-com headquarters.
It doesn’t matter if a garage is used for fossil fuel-burning cars, hidden dangers can lurk within. You can’t allow a garage fire to spread to other houses, regardless of whether you follow only the suggested or mandated standards of practice. You also don’t want carbon monoxide to enter your home if your car is parked in the garage.
Garages attached to homes can pose a host of hazards. There are many dangerous substances that homeowners store in their garages. There is a possibility that volatile chemicals or hazardous gases, other than gasoline and diesel fuel, may be present in the home. These chemicals include paint accessories chemicals such as thinners and removers. They also include propane cylinders for barbecue grills. Swimming pool chemicals. Welding gases for gearheads and welders.
This is made worse by carbon monoxide (CO), and other vapor accumulations within garages. Although fire separations are required between attached garages and residences, they are not clearly defined in the current building codes. They are not always constructed properly, don’t perform as intended and pose a fire safety risk for homeowners. Curiously, the building codes do not include any mention of gases or vapors other that CO. Safety is not always maximized, even when the relevant building codes are properly designed.
Separation codes
The IRC doesn’t provide a definition of “fire separation”, which is required by 302.6. It is possible to suppose that it refers to a modified fire-resistance arrangement, but it does not necessarily constitute a fire resistant or fire-rated assembly per se. It isn’t an assembly, some would argue. There is an interior and garage requirement for 1/2-inch gypsum boards. Also, 302.9 requires a minimum flame-spread index and smoke-developed index for the gypsum board finish on both ceiling and fire separation walls.
IRC (International Building Code) and IBC (International Building Code) have been lacking a glossary that is comprehensive or even complete. This often leaves interpretation of code citations to code officials and contractors who may not be qualified to interpret the intent or meaning of code authors. It is our duty as inspectors to ask the International Code Council (ICC), to provide all parties with a more comprehensive chapter of definitions in their respective code publications. They might publish an all-inclusive, standalone glossary if they fail to do so.
Other than Gypsum Board Ceilings and Walls
In many cities, especially in Dallas-Fort Worth, building officials have equated 7/16-inch OSB and 1/2-inch Gypsum Board for ceiling separations and garage walls. They are not the same materials when it comes to flame spread ratings (FSR). 1/2-inch Gypsum board is rated at 10 and 7/16-inch OSB at 150. Even if OSB is installed over required gypsum boards, it would not be code compliant as the OSB will then become a wall covering that requires an FSR at least 50.
Wall Finishes and Ceilings
According to the code authors, “fire resistance” is defined as “that property of materials and their assemblies that prevents, retards, or emits heat, hot gases or flames under certain conditions of use.” IRC 302.9 states that garage separation ceilings and wall finishes must adhere to minimal flame-spread or smoke-developed index ratings.
Doors
The entry door that connects the garage to the house is one example of a problem area. The door assembly itself is not required to be fire-rated. You could argue that a fire-rated or equivalent door is necessary, as per IRC 302.5.1.
The need to fire resistant the door frame is not mentioned. The need to weatherstrip (gasket) the door is not mentioned. Closure devices are required. These could be spring hinges, or hydraulic closures.
Toxic airborne chemical vapors can pass through garage doors if they are left open. Poorly designed HVAC systems or the chimney effect can cause significant negative pressures inside homes. This can lead to fumes from garages being drawn indoors through small openings on separation walls and ceilings or around doors that are not properly sealed.
Newer homes have been air sealed for greater energy efficiency. If done correctly, it can help to prevent the intrusion of noxious gases from attached garages. Older homes may not have adequate protection. Homeowners and buyers should be instructed by inspectors to seal their garage walls and ceilings. They should also store toxic and flammable chemicals in fireproof containers. Garage ventilation should be provided to eliminate any unwanted fumes from the outside.
International Mechanical Code (IMC) 403.3 requires ventilation. Although this requirement is not applicable to single-family residences in most cities, an inspector might want to mention it in his inspection report to give the client options beyond what the IRC requires.
Plumbing Penetrations
In many garages, the installation of PEX water supply pipes manifolds is a common practice. These are also common in homes with fire suppression sprinkler systems. These are typically just holes in the drywall that have been framed with scrap material and covered with plywood, OSB doors or plywood. These manifolds are often stuffed with insulation and declared code-compliant by builders. This practice can actually be a fire hazard. Inspectors should urge clients to cover these openings with 1/2-inch gypsum boards or 16-gauge metal access doors. These are designed for fire-rated walls. If a door in a fire separation does not have a fire resistant seal, it is ineffective.
Attic Pull Down Stair Units
A ceiling fire separation breach can be seen in the near-an-attic pull down stair unit. These units are typically made of softwood frames and covered with 1/4-inch Philippine mahogany (often called luan, lauan or meranti and not being related to real mahogany). This plywood’s flame spread rating (150) is not nearly as high as the required 1/2-inch gypsum board (10), for garage ceilings above the attic, or the Type X gypsum board (15) for ceilings above the living area. You can choose from a variety of pull-down stair designs that are fire-resistant or use metal panels. Weatherstrip must be applied to the door from all four sides, including the hinge side. Any trim used around the perimeter should have the approved flame spread rating.
Electrical Penetrations
The outlet boxes and electrical panels are also important openings that should be inspected during fire separation inspections. These are not fire-resistant or fire-rated components, so the IRC does not mention them in garage fire separation. Imagine an electrical outlet box with a gap of 1/8 inch between it and the gypsum board and openings for the cables to enter and exit the box. The box may be UL-rated to allow installation in a fireproof or fire-rated assembly. However, the openings in and around the box create a pathway for smoke, fire, and vapor intrusion. These openings should be blocked by inspectors.
IRC and National Electric Code do not require the sealing of electrical panels or junction boxes within fire separation walls. This is a requirement for fire-resistant and fire-rated electrical assemblies. These methods should be recommended to clients who live in single-family homes or are considering purchasing them.
Floor Coverings and Floor Tiles
Garage floors should also be considered. They must slope to allow liquids to drain towards the garage door opening. Engineers recommend a slope of 1%, or 1/8 inch per foot.
The IRC defines “non-combustible” as “materials that meet the requirements for non-combustibility for elementary materials set forth by ASTM E136.” It applies to the base material (usually concrete in the case garage floors) and does not cover any coatings or surface coverings. The model building codes define non-combustible materials as those that have a covering. This means that the base material must meet the ASTM E136 requirements and that the surface must not exceed 1/8 inch in thickness. It should also not have a flame-spread index greater than 50. Garage floor coverings are often more flame-spread than 50.
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