Plywood/sheetrock garage firewall

Am repairing an old house and have question about attached garage wall.

House did have sheetrock on both sides of studs of house/garage wall.
All exterior walls are currently open so that I can install insulation (had none) and replace outdated wiring.

Heard a suggestion about mounting 3/4" plywood to garage side of shared wall to facilitate easier mounting of shelves and hooks for tools and such without having to locate studs. I also like the idea of providing a more solid surface between garage and home. (ie., Burglar or nailgun could easily pass thru two layers of drywall).
I assume the plywood would have to be covered with 1/2" drywall.
Also understand that the firewall either has to extend up to roof or simply cover the garage ceiling.
My concern about taking it up to the roof is how it might affect attic ventilation. One of the gables is located above the garage ceiling.


Yes, it must be covered but Code is… 5/8 inch fire rated drywall.

You do not need to go all the way up to the roof. Simply install it to the ceiling and end it there. Your gable end vent will be fine above this 5/8 " fire-rated ceiling.

Here’s an illustration for proper fire-proofing in a garage…

“Click to Enlarge”

Garage ceiling only has to be 5/8" X if living space is above it.

  • Min [1/2" IRC] {5/8" UBC} gypboard on garage side of walls common to house.
  • Min [5/8" IRC & UBC] gypboard on garage ceiling common to house.

Best check local code adoption prior to work to insure your work is for not.

Simplest measn is to install drywall that meets firecode to the studs then install plywood OVER the drywall to hang your stuff.