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Garage fire wall / separation wall between the house and an attached garage is very often mistreated by the home owners.
I’m assuming that they are simply unaware of the fire safety requirements and how critical it might be to gain those extra minutes that garage fire wall should provide in case of fire.
As always. check your local jurisdiction requirements, because they might exceed the IRC (International Building Code).
#1. Garage fire wall / separation wall – materials used on the garage side of walls and ceiling common to the house must meet certain requirements in order to slow the spread of fire. IRC (International Building Code) specifies that single and 2-family building must have a one hour rated surface, half an hour if an automatic sprinkler system has been installed.
In order to achieve this garage wall fire rating, the house – garage common wall needs to be sheathed with at least 1/2″ thick drywall, and the ceiling surface requires minimum 5/8″ thick, type X gypsum board.
All drywall seams must be taped / finished with joint compound and some jurisdictions might require fire rated joint tape for this purpose.
The garage fire wall should have no missing / damaged drywall sections, any penetration must be sealed (fire rated caulking would be perfect for small gaps around the pipes, air ducts, door frames, etc). If the wall is made out of brick, cinder block, stone, solid concrete, or any other non-flammable material, you’d just have to worry about penetrations.
Garage fire wall penetrations:
#2. Entry doors from the garage into the house – they must be at least 20 minute fire resistance rated, or 1 3/8″ solid core doors – no hollow core, interior type doors like the ones that you normally install in bedrooms, closets, bathrooms, etc.
Doors require proper weather stripping to create an air tight barrier between the garage and a living quarters.
One more feature that helps to preserve the garage fire wall is a self closing door. Although, I always recommend it to my clients purchasing older homes, self / fully closing garage door is required on a new construction in many jurisdictions for several years already.
I don’t think that any local code enforcement division would force a homeowner to upgrade in an older home, but it makes sense to do such an update for your own sake. It is a very small investment (around $30.00), and all you need to do is replace a couple of regular door hinges with a spring type and adjust the door so it will fully close automatically.
It is for your own safety … I know that nothing bad ever happens to you, but just in case somebody forgets to turn off the car engine and leaves the door between the garage and the living quarters open … you won’t smell Carbon Monoxide …
#3. Another requirement for the entry door from the garage into the house is to be slightly elevated / higher than the garage floor surface. Many building codes require a step (or curb) between the house door and the garage floor. The step (min 4″ recommended, but check your local code) prevents spilled gasoline vapors from entering the house and partially protects residents from carbon monoxide fumes.
There should be no openings between the garage and rooms used for sleeping purposes.
#4. A forced air heating system distributing air through the house with a register (supply or return) open in the garage violates garage fire wall - older homes often have them installed. They should be removed and the air duct opening sealed with sheet metal and fire rated caulking.
Metal air ducts exposed in the garage area should be at least 26 ga. steel, no plastic or aluminum (thin wall or flexible type) vent hoses penetrating the separation walls are permitted – if there’s no other way to run those vent pipes, insulate it, box it out and finish it with 5/8″ drywall (Type X, taped).
#5. An electrical box installed in the garage fire wall with another one connected to its back - back to back installation with one side serving garage and other serving the house. Also, some jurisdiction might not allow having an electrical panel installed inside the garage fire wall.
#6. Garage floor must be non-combustible material and sloped towards the floor drain or overhead doors. I’ve seen many garages with a carpet installed …
#7. Attic access installed in the garage is an important part of a fire wall. Even if the garage attic is completely separated from the house attic or house walls don’t back-up to it, open access creates a vacuum and garage fire will be sucked into the attic – keep it closed at all times.
Many single story homes with an attached garage have no ceiling in the garage section and an open attic above the house. In such case the garage fire wall / house separation wall should extend all the way to the roof decking or garage section should have a 5/8″ drywall ceiling installed.
Typical garage attic access (at least in the majority of Chicago land homes including new construction) is a square drywall section, usually set on four pieces of trim. Drywall is fine, but the trim neither provides a proper seal nor has a required fire rating … it would most likely burn within a few minutes …
Another “gap” in the garage firewall is a pull-down type staircase to the attic - most of these have only a 1/4″ or 3/8″ paneling sheet installed and rarely provide proper seal along the opening – have your local code enforcement division comment on it if your garage attic opens to the house attic space.
Many older homes do not comply with those garage fire wall requirements, and of course – I’d highly recommend to do all of the necessary improvements – it’s better to be safe …
Many more garage tips in garage door opener safety and garage door springs safety posts – it’s so easy to test and protect yourself.
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