One of the exterior walls of my garage is directly next to a neighbor's structure. Thus, I don't have access to this external side. I want to cover the inside of my garage walls with 3/4" plywood. Is there anything I need to do with the stud cavity before slapping plywood on?

It is currently not insulated and I don't have plans to insulate the garage.

The wall has a paper backing which is missing in some places (see photo). Is it possible this is the exterior house siding attached directly to studs? Home was built in 1955. interior garage wall

  • Is the garage attached to your house or a freestanding building?
    – mikes
    Jul 31, 2019 at 21:42
  • Attached. Garage is street level, main living area is above garage.
    – dabi
    Jul 31, 2019 at 22:02
  • 2
    Depending on local building codes you may be required to install fire resistant sheetrock or similar material as it is attached. Your current setup may be grandfathered but modifications may not be allowed.
    – mikes
    Aug 1, 2019 at 0:44

2 Answers 2


Yes, with the diagonal bracing and the uniform horizontal boards of which some were replaced, along with the "paper" that has some missing spots that just happens to be were damaged boards/siding used to be, I would say it is a safe bet that was the exterior of the garage at one time before the neighbors house was built.

If it were my garage and I wanted to put plywood on the inside, I would do so. If an inspector sees it, and cites you for it, then add the firecode sheetrock. Even so, adding a layer of plywood adds another layer of protection between properties.

  • As someone who once lived in a house with a 1950's garage matching the OP's construction that burned in a fire, I would suggest doing the right thing now in terms of fire protection instead of just slapping (flammable) plywood on the wall and hoping you don't get caught.
    – dwizum
    Aug 1, 2019 at 14:19
  • @isherwood, is this for me? But while I am here and not wanting to waste my space good for 600 characters, (they upped the count!) 3/4" plywood is accepted for use as fireblocking along with 2X material and Type X sheetrock for firestopping. At least it was at on time. The way I see it Type X is good for an hour, code requires doors to be rated for 20 minutes and 3/4" plywood is somewhere in between there. Besides, adding plywood to a garage wall instead of drywall will not mean the garage will catch on fire, I feel for dwizums concerns, but catching fire, is unlikely, Lord willing....
    – Jack
    Aug 2, 2019 at 4:31
  • I think maybe I misread your second paragraph. Sorry.
    – isherwood
    Aug 2, 2019 at 12:58

Protect Wires

If there is any electrical wiring on that wall, it needs to be protected from accidental damage - e.g., nails/screws. The rules apply even with the walls open, but then it is quite obvious where the wires are so it is not an issue. Typically this includes, for wires not in metal conduit:

  • Cables should be run through holes in the middle of studs, not run in front of studs (which would then be right behind your plywood and really vulnerable to damage)
  • Metal plates in front of cables where they run through studs
  • Cables properly secured

There are some similar concerns with water or gas pipes as well.

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