Garage to House Fire-Resistance -- King of the House Home Inspection, Bellingham, WA
Fire-resistance requirements between homes and garages are based on building codes. A home inspector is not a code inspector, or a code expert, but it is helpful for any inspector to understand the basic guidelines established by the International Residential Code (IRC). Excerpts from the code are pasted below, and under the quotes, I have added my interpretation of applicable code.
"Unlike separations between dwelling units, the separation between a residence and a garage is not a fire-rated assembly."
Interpreted: Garages are subject to less stringent fire-resistance separation requirements than residential dwelling units such as condos and townhouses.
"Attached garages, or garages within 3 ft of the house, shall provide "limited resistance" to the spread of fire. Usually that involves installing suitable drywall on the garage to house wall. If there are habitable rooms over the garage, drywall should, also, be installed at the garage ceiling and on the bearing wall that supports the ceiling framing."
Interpreted: The proper terminology is "limited resistance to the spread of fire." Installing drywall at shared walls, between a garage and the house, usually satisfies basic requirements. If the attic over the garage is open to the attic over the dwelling, or if there is a habitable room over the garage, drywall (or another noncombustible surface) is required at the garage ceiling and on the wall that supports the ceiling framing.
The flammable plywood attic access cover, in the photo above, is a breach of limited fire-resistance at this attached garage ceiling.
"Doors between the house and garage provide some resistance to the spread of fire but they do not require a fire-resistance rating. Any one of the following doors is acceptable: 1 3/8" thick solid-core wood/solid-core steel/honeycomb-core steel door or any door listed by the manufacturer as fire-resistant."
Interpreted: The garage to house door must conform to certain specifications, but it need not be fire-rated -- a wood door is acceptable if it is solid core and thick enough to comply with minimum guidelines.
Over the years, many garage to house doors have been equipped with self-closing devices. In fact, some door manufacturers' state that, to maintain a fire-resistance rating, a door must self-close. Therefore, unless the weight of any given door could pose a safety risk to a child (impact injury as door swings shut), a self-closing device is a beneficial upgrade. After all, a fire-resistant door hanging wide open, photo above, is of little value.
"Openings from the garage into a sleeping room are prohibited".
Interpreted: Doors or windows, any openings from the garage, cannot lead into bedrooms.
"Ducts that run into, or through, the garage shall be made of sheet steel and the ducts may not open into the garage. Steel or plastic pipes, run through the garage, must be sealed, at wall or ceiling penetrations, with fire-resistant caulking".
Interpreted: Acceptable garage ducts are made of steel and they cannot open into the garage. Any openings around penetrations must be filled with fire-resistant caulking (see material around B-vent in above photo). The heat supply duct/register (photo below) is not acceptable since it is located in the garage.
The hole in the wall around the metal conduit, above photo, is yet another problem. Finally, garage floors (typically concrete slabs) should be non-combustible and, if a crawl space access opening has been cut into an interior garage wall, the hatch cover must be made of a non-combustible material.
The plywood crawl space hatch cover, photo below, is an obvious deficiency in the fire-resistance at the wall.
Bottom line: An attached or a built-in garage, or any garage within 3 ft of the house, must be designed in a manner that provides limited resistance to the spread of fire. To learn more about the topic of fire-resistance, please click on the video link below.