Type X Drywall and Where the Code Wants It

Where the code wants it

Table R302.6 in the 2018 residential code’s fire-separation chapter, as published for Tennessee, lays out the garage. The wall to the house and the attic over the garage get at least half-inch gypsum board on the garage side. Where habitable rooms sit above the garage, the ceiling gets five-eighths Type X, and the walls and beams that hold that ceiling up get at least half-inch board. A door into the house has to be solid wood or solid or honeycomb-core steel at least 1-3/8 inches thick, or a 20-minute fire-rated door, with a self-closing or automatic-closing device, so a hollow-core interior door does not qualify, and no door may open from the garage straight into a bedroom. Ducts through the separation must be at least 26-gauge sheet steel or another approved material, with no openings into the garage. That is the 2018 text; Metro now works from the 2024 edition and its own amendments, so ask Metro Codes what applies to your house and your permit.

The same chapter reaches a few other places. A closet or storage space under a stair gets half-inch gypsum board on the enclosed side. The two units of a duplex are separated by wall and floor assemblies with at least a one-hour fire-resistance rating, and townhouse walls follow their own section. Keeping fire out and keeping noise out are separate jobs, and if the complaint about a wall between rooms is sound, our post on soundproofing an interior wall that is already built ranks what actually cuts it. A detached garage less than 3 feet from the house gets at least half-inch board on the inside of its exterior walls within that distance. The table’s wall rules do not apply to a garage wall that runs perpendicular to the wall of the house.

• Garage side of the wall and attic next to the house: half-inch board or thicker
• Garage ceiling under habitable rooms: five-eighths Type X
• Walls and beams holding up that ceiling: half-inch board or thicker
• Wall and floor between duplex units: one-hour rated
• Enclosed space under a stair: half-inch board on the enclosed side
• Detached garage within 3 feet of the house: half-inch board on those walls

How is a garage fire separation patched?

A patch in the garage separation uses the same type and thickness of board as the sheet around it, attached the way the code’s fastening table, R702.3.5, calls for. We back the cut edges with framing or strips so the patch is fastened on every side, then tape and finish the joints so the repair reads as part of the wall. Holes for wires and pipes get filled with an approved material that resists the passage of flame and products of combustion, which is how the ICC interpretation reads Item 4 of R302.11. We use a fire-rated caulk or putty for that, and Metro Codes has the final word on what counts as approved. The way we close a trade’s hole in an ordinary wall is in our post on the hole a plumber or electrician left.

If the wall or ceiling has been patched many times with the wrong material, the honest repair is often to strip it and hang it again, which in a single-car garage is a modest job. It is the same drywall repair work we do anywhere else in a house, with the board chosen by the code. When you ask us for an estimate, tell us the wall is the garage separation and whether there are rooms over the garage, since that decides whether the ceiling gets Type X.