Recent construction requires a firewall between any portion of the garage that abuts the home's living area. This firewall should extend up to the roof deck if the garage ceiling is not drywalled. The drywall material is required to be rated type “X” or a minimum of 5/8″ in thickness which will allow for about one hour burn time before failing. Why do they require this? There are two main reasons for this requirement. In the event of a garage fire it will give the occupants more time to exit the home. The second reason is it contains the fire longer which in turn gives the fire department more time to get to your home which can limit damage.
One area that is often a void in this firewall is garage attic ladders that are installed after the home has been built. An area of drywall is cut out between the rafters and the ladder is installed thus removing approximately a 2’x4′ section of the firewall. Usually these ladders are centrally located in the garage which can be right over the top of where cars are parked. Guess where a fire in a car generally occurs? You guessed it, in the engine compartment right below the attic ladder. This is not a good situation as the fire can race directly into the attic space which is often connected to the homes attic space. This is a very common issue I run into in home inspections. Remedy for this is easy, cut a section of drywall slightly larger than the back of the ladder and screw it to it. There are still voids around the seam for the opening but it is certainly better than the 1/4″ piece of plywood that comes with the unit. Any other holes through the firewall should also be sealed with a flame retardant sealant. In older homes the drywall is often installed but has never been taped or mudded. This is a requirement these days.