Attached Garage Hazards

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An attached garage is a garage that is physically attached to a house. Fires that begin in attached garages are more
likely to spread to living areas than fires that originate in detached garages. For this reason, combined with the
multitude of flammable materials commonly found in garages, attached garages should be adequately sealed from
living areas. A properly sealed attached garage will ideally restrict the potential spread of fire long enough to allow
the occupants time to escape the home or building.

Why are garages (both attached and detached) fire hazards?

Oil or gasoline can drip from cars. These fluids may collect unnoticed and eventually ignite.
Flammable liquids, such as gasoline, oil and paint, are commonly stored in garages. Some other examples are
brake fluid, degreaser, motor oil, varnish, lighter fluid, and fluids containing solvents, such as paint thinner.
These chemicals are flammable in their fluid form, and some may create explosive vapors.
Heaters and boilers, which are frequently installed in garages, create sparks that can ignite fumes or fluids.
Car batteries, too, will spark under certain conditions.
Mechanical or electrical building projects are often undertaken in the garage. Fires can easily start while a
careless occupant is welding near flammable materials.

Doors
The 2006 edition of the International Residential Code (IRC) states the following concerning doors that separate
garages from living areas:

R309.1 Opening Penetration
Openings from a private garage directly into a room used for sleeping purposes shall not be permitted. Other
openings between the garage and the residence shall be equipped with solid wood doors not less than 1-3/8” (35
mm) in thickness, solid- or honeycomb-core steel doors not less than 1-3/8” (35 mm) thick, or 20-minute fire-rated
doors.

In addition, inspectors can check for the following while inspecting doors that separate garages from living areas:

While not required by the IRC, it is helpful if there is at least one step leading up to the door from the garage.
Gasoline fumes and other explosive gases are heavier than air, and they will accumulate at ground level. Their
entry beneath a door will be slowed by an elevation increase.
Doors should have tight seals around their joints to prevent seepage of fumes into the living areas of the
house. Carbon monoxide, with the same approximate density as air (and often warmer than surrounding air),
will easily rise above the base of an elevated door and leak through unsealed joints.
Doors should be self-closing. Many homeowners find these doors inconvenient, but they are safer than doors
that can be left ajar. While this requirement is no longer listed in the IRC, it is still a valuable recommendation.
If doors have windows, the glass should be fire-rated.
Pet doors should not be installed in fire-rated doors. Pet doors will violate the integrity of a fire barrier.

Walls and Ceilings
The 2006 edition of the IRC states the following concerning garage walls and ceilings:

R309.2 Separation Required
The garage shall be separated from the residence and its attic area by not less than ½-inch (12.7 mm) gypsum
board applied to the garage side. Garages beneath habitable rooms shall be separated from all habitable rooms
above by not less than 5/8-inch (15.9 mm) Type X gypsum board or equivalent. Where the separation is a floor-
ceiling assembly, the structure supporting the separation shall also be protected by not less than ½-inch (12.7 mm)
gypsum board or equivalent. Garages located less than 3 feet (914 mm) from a dwelling unit on the same lot shall be
protected with not less than 1/2–inch (12.7 mm) gypsum board applied to the interior side of exterior walls that are
within this area. Openings in these walls shall be regulated by Section 309.1. This provision does not apply to
garage walls that are perpendicular to the adjacent dwelling unit wall.

In addition, inspectors can check for the following while inspecting walls and ceilings:

In garages that have access to the attic, a hatch cover made from an approved, fire-rated material should
protect this access at all times. Missing or opened covers should be called out, as should covers made from
flammable materials, such as thin plywood. Garage attic door must be constructed such that the 45 minute
rating is maintained; any drywall edges on both the hatch and the surrounding area exposed to physical
damage are protected. The cover or door is installed so that it is permanent (non removable) with hardware to
maintain it in a closed position with latching hardware to maintain it in a closed position. This could be
accomplished by the use of spring loaded hinges, door closer, or hardware that will not allow it to be left in an
open position when not in use. A single bolt type or hook and eye hardware does not provide a positive
closure since these would allow the door to be left open. Likewise drywall screws are "fasteners" and not
hardware so they cannot be used as the only means of keeping access doors closed.
The living space is separated from the garage by a firewall that extends from the floor to the roof. If the ceiling
material is fire-rated, the firewall can terminate at the ceiling.
Drywall joints shall be taped or sealed. Joints shall be fitted so that the gap is no more than 1/20-inch with
joints backed by either solid wood or another layer of drywall such that the joints are staggered.

Ducts
The 2006 edition of the IRC states the following concerning ducts that penetrate garage walls and ceilings:

R309.1.1 Duct Penetration
Ducts in the garage and ducts penetrating the walls or ceilings separating the dwelling from the garage shall be
constructed of a minimum No. 26 gauge (0.48 mm) steel sheet or other approved material, and shall have no
openings in the garage.

Dryer exhaust ducts that penetrate garage walls are serious fire hazards. These ducts are generally made from
plastic and will easily melt during a fire, creating a large breach in the firewall.

Floors
The 2006 edition of the IRC states the following concerning floors in garages:

R309.3 Floor Surface
Garage floor surfaces shall be of approved, non-combustible material. The area of the 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.

Inspectors should also check for the following:

A curb is present along the perimeter of the garage floor. This curb is designed to prevent fluids from entering
the living areas of the house. Curbs are often useful barriers for melted snow carried into the garage by
automobiles, but curbs can also keep chemical spills contained in the garage.
Water heaters should be elevated above the floor by at least 18 inches. A pilot light may ignite spilled fluid or
floor-level flammable fumes if the water heater is placed at floor level.

Concerning items placed on the floor, inspectors should check for the following:

All flammable liquids are stored in clearly labeled, self-closing containers, and in small amounts. They should
be stored away from heaters, appliances, pilot lights and other sources of heat and flame.
Propane tanks should never be stored indoors. If they catch fire, a serious explosion may result. Propane
tanks are sturdy enough to be stored outdoors.
The floor should be clear of clutter. Loose papers, matches, oily rags, and other flammable items are
dangerous if they are strewn about the garage floor.