A common mistake that home inspectors make when inspecting single family residences is related to opinions stated about the requirements for separation between the home and the attached garage.
Their comments often leave them “out on a limb” when repairs are called for and a builder or repair person informs them there are no “fire-rated” requirements.
I should clarify, this article is based on 2015 IRC and may not be consistent in every regard with the codes amended or otherwise in your area.
I routinely hear erroneous statements about compromised “fire-rated surfaces” between the house and the garage. Also common are statements declaring surfaces between the house and the garage are not “1 hr fire-rated,” or that the “1 hr fire-rated surfaces” are in some way compromised.
The wall between the house and the garage–believe it or not–is NOT a fire-rated assembly and is referred to in the code as the “Dwelling-Garage Separation.”
Meeting the “separation” requirements is really quite simple and minimal compared to what would be necessary in an actual “fire-rated assembly” (As would be required between multiple dwelling units like condos, townhouses and duplexes etc.)
Typically, ½” drywall (or equivalent) is all that is necessary to meet the separation requirement.
If there is living space above the garage, the ceiling would have to be 5/8” type “X” drywall (or equivalent). Again, this is not a “fire-rated assembly,” but merely what is required to meet the proper “separation” requirements.
These wall and surface finishes have to have a flame-spread index not greater than 200, however wood frames and trim around doors and windows are excluded from this requirement.
Duct-work inside the garage, or duct-work that runs through these fire-resistant surfaces must be constructed of minimum No. 26 gauge sheet steel or other approved material and shall not have openings into the garage. So this means no return air registers or heat supply registers inside the garage.
Openings around other types of penetrations in the walls and ceilings (ductwork, pipes, wires, etc) must be filled with an approved material to resist the free passage of flame and products of combustion. There is nothing in the code, for single family residential construction, that prohibits plastic piping through these fire-resistant surfaces. This is another common incorrect call-out by home inspectors. The openings around them merely have to be properly sealed.
Pull-down stairs in a garage ceiling would be required to meet the requirements of 1/2 drywall or equivalent, or have a 20 minute fire-rating.
The door or doors placed in this “separation” are also frequently misunderstood and incorrectly reported on.
For the door between the house and the garage, all that is necessary is to install a door that meets the “separation requirements” of the code. Of course this door can never lead to a bedroom.
There is nothing that says it has to be a “fire-rated door,” as frequently reported by home inspectors.
While this may seem confusing, if one looks at the code it becomes clearer. It also reveals the source of some of the confusion.
To meet separation requirements, the door must be one of three types of doors: a solid wood door not less than 1-3/8 inches thick, a solid or honeycomb core steel doors not less than 1-3/8 inches thick, or a 20-minute fire-rated door, with a self-closing device. Another thing to note, is that a 1-3/4″ thick solid wood raised panel door would likely not comply because the minimum thickness at the recesses would likely be less than 1-3/8.”
As a side note, that little comma after “door” in: “door, with a self-closing device,” is consistent with its pertaining to all three choices–not just the 20-minute type door. If it applied to only that type of door the comma should not be there.
The first two types are fairly self explanatory but the inclusion of the third type has lead to a great deal of confusion because a door that is a “20-minute fire-rated door” leads one to think that the door in general, and thus the walls and ceiling, have to somehow be “fire-rated.”
Also having a “fire-rating” (as all materials in the home do) does not make any of this a “fire-rated assembly.” It just means the fire-resistant surfaces are specified to be constructed of materials known to have known fire-resistant characteristics.
For a door to achieve a 20-minute fire-rating it has to go through testing procedures by Underwriters Laboratories and then it receives its “UL listing” as a fire-rated assembly.
All three types of doors will require weather-stripping/seals on all four edges of the door to prevent the passage of gases that may be drawn into the home, as well as meet energy efficiency standards.
Hopefully this post will help clear up some of the confusion.
Charles Buell, Real Estate Inspections in Seattle