If there is no ceiling and the roof structure is exposed in the garage then the wall separating the garage from the dwelling must extend up to the underside of the roof sheathing.
Garage firewall attic access.
In such case the attached garage firewall house separation wall should extend all the way to the roof decking or garage section should have a 5 8 drywall ceiling installed.
There is a high incidence of fires started in garages due to the gasoline and other flammable materials often stored there and either way the intent is create a 1 2 drywall barrier between the garage and house for fire protection.
Each of these materials is combustible so having a wooden access cover separating an attic and garage compromises the fire separation.
When installed in a garage ceiling this thin wooden membrane replaces a portion of the fire resistant drywall.
R302 6 dwelling garage fire separation.
The door is required to be self closing.
This also applies to structural members and this extends to the attic in a common sense type of way.
The access cover on a folding ladder is usually a mere piece of inch plywood.
A common defect i that run across sometimes even in newer homes is when there is attic space above the garage and the access cover from the garage consists only of a piece of particle board osb or plywood.
The wall between a house and garage must be separated by 1 2 drywall.
In situations where there is attic access either to the house attic from the garage or to the garage attic through the ceiling difficulties can arise.