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Building Code Reference

Got a CRC R302.6 correction?

Garage drywall requirements

For builders in California, Greater Seattle, the Las Vegas area, the Denver area and Kansas City · CrossBeam Permits

What this code requires, how to fix it, and how cities and counties review it

What this code requires

CRC R302.6 is the California Residential Code section that sets the fire-separation requirements between an attached garage and the living space of a dwelling. Garage walls shared with the house require at least 1/2-inch gypsum board on the garage side. When any part of the dwelling unit sits directly above the garage, the ceiling requires 5/8-inch Type X gypsum board. All penetrations through those assemblies must be protected per R302.5. ADUs with attached garages, single-family homes with bonus rooms over the garage, and remodels that convert garage space all trigger this section.

How to fix it

  1. Identify all garage-to-dwelling separation surfaces

    Walk the plans and mark every wall, ceiling, and floor-ceiling assembly where the garage shares a surface with any habitable room, hallway, or utility space inside the dwelling. This includes the common wall between the garage and the house, the ceiling below a bedroom or bonus room over the garage, and any knee walls where the garage attic space meets habitable areas. If the garage is below a second-floor room, that whole ceiling assembly is in scope for R302.6.

  2. Specify 1/2-inch gypsum board on garage-side walls

    Any wall surface on the garage side of the separation must be covered with minimum 1/2-inch gypsum board. Note this explicitly on the floor plan with a dimension callout and a material note — "1/2" GWB on garage side, per CRC R302.6" is the standard note form plan-checkers look for. Don't just write "GWB typ." without the thickness; the checker can't infer the minimum from a general note.

  3. Upgrade the garage ceiling to 5/8-inch Type X when rooms are above

    When any portion of the dwelling unit sits directly over the garage, whether a habitable room, hallway, bathroom or closet, the garage ceiling below it must be 5/8-inch Type X gypsum board. Add a ceiling plan or section detail that calls this out with the notation "5/8" Type X GWB, garage ceiling per CRC R302.6." If the floor-ceiling assembly is already framed and you're remodeling, confirm whether the existing board meets Type X by checking the board's edge stamp or face stamp before the inspection. Generic drywall and Type X are not interchangeable.

  4. Detail every penetration through the separation assembly

    Every hole through the garage-dwelling separation wall or ceiling must be protected. R302.5.3 sends these penetrations to R302.11, Item 4: an approved material that resists the passage of flame around pipes, wires, vents and flues. Ducts are different: R302.5.2 requires No. 26 gauge sheet steel or other approved material with no openings into the garage. For each penetration shown on mechanical, electrical, or plumbing sheets, add a callout that names the method or product. A note like "all penetrations through R302.6 separation protected per CRC R302.5.2 and R302.5.3" covers the set broadly; individual callouts per penetration are cleaner but either approach typically satisfies the plan-checker.

  5. Address attached structures that share the garage envelope

    Covered breezeways, laundry rooms, or storage rooms that open directly into the garage share the same separation requirements as the main dwelling. If the plans show a door from the garage into a laundry room that connects to the house, that laundry room is part of the dwelling: the separation is the garage-side gypsum board on the shared wall and ceiling, plus the door per R302.5.1. Confirm each space's status in the plans and add notes accordingly.

  6. Confirm the garage door opening per CRC R302.5

    The door between the garage and dwelling is governed by companion section R302.5, but plan-checkers reviewing R302.6 often catch the door spec at the same time. Make sure the door is shown as solid wood at least 1-3/8 inches thick, solid or honeycomb-core steel at least 1-3/8 inches thick, or a 20-minute fire-rated door. If your resubmittal is fixing the drywall spec, confirm the door spec is correct in the same pass to avoid a follow-up correction on the same assembly.

  7. Add a code compliance note to the cover sheet or general notes

    A visible note on the cover sheet or the general notes page that reads "Garage-dwelling separation per CRC R302.6: 1/2" GWB on garage walls; 5/8" Type X on ceiling below any part of the dwelling above; all penetrations protected per R302.5" gives the plan-checker a fast verification path. Some cities stamp this as met and move on; without it, they flag each surface individually and the correction letter comes back longer than it needs to.

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Why you got flagged

Plan-checkers flag R302.6 most often when the plans say "drywall garage" without specifying the type or thickness. A note that reads "1/2" GWB, typ." on the floor plan satisfies the wall requirement, but if there's a bedroom, office, or storage loft above the garage, the ceiling assembly needs to be called out separately as 5/8" Type X. Missing that distinction is the most common single-line correction on garage-adjacent projects.

The second scenario is a garage conversion or ADU addition where the original garage ceiling was never documented. When a permit reviewer looks at the existing conditions, they can't confirm the ceiling assembly meets the Type X requirement, so they flag it. The fix is usually adding a detail sheet or a note on the demolition plan that confirms the existing assembly, or scheduling a special inspection to verify the drywall type in the field before closing walls.

The third scenario involves penetrations. A water heater flue, electrical conduit, or recessed light passing through a garage-dwelling separation needs protection at the penetration per R302.5.3, using an approved material under R302.11, Item 4. Drawings that show the mechanical or electrical runs but don't call out the protection method at each penetration get flagged under R302.6 even when the drywall itself is correctly specified. Plan-checkers want to see the firestop product or method noted on the sheet, not left to field interpretation.

A fourth situation: when a garage is being converted to habitable space, contractors sometimes pull a separate ADU or addition permit but forget that the adjacent garage wall that remains now needs to comply with R302.6, with the gypsum board on its garage side. The wall that used to be interior suddenly becomes a separation wall, and it needs to be documented accordingly on the revised plans.

The official code

California Residential Code R302.6 — Dwelling/Garage Fire Separation (2025 edition, Title 24 Part 2.5)

Read the source →

Common questions

Does CRC R302.6 require 5/8 inch Type X on all garage walls?
No. The 5/8-inch Type X requirement only applies to the ceiling below portions of the dwelling unit that sit directly above the garage. Garage walls shared with the dwelling need 1/2-inch gypsum board on the garage side — not Type X. You only step up to Type X when there's occupied space above. If the garage has no room above it, 1/2-inch standard drywall on the shared walls satisfies R302.6. One note: the garage ceiling that has no room above it also only needs the 1/2-inch minimum — the upgrade is triggered by what's above, not by the garage being a garage.
Do detached garages need to comply with CRC R302.6?
Mostly no. CRC R302.6 is aimed at attached garages that share a wall, ceiling, or structural assembly with the dwelling. A detached garage does not need that separation, with one exception in Table R302.6: a garage less than 3 feet from a dwelling unit on the same lot needs 1/2-inch gypsum board on the interior side of its exterior walls within that area. However, if a detached garage has an accessory dwelling unit above it or is connected to the house by a covered walkway or enclosed breezeway, those connections may bring it into scope. Check the actual structural connection and any occupancy above before assuming it's exempt.
Can I use two layers of 1/2-inch drywall instead of 5/8 inch Type X?
No. Two layers of 1/2-inch standard drywall do not substitute for 5/8-inch Type X gypsum board. Type X has fiberglass reinforcement and a specific core formulation that gives it the rated fire-resistance — total thickness alone doesn't replicate that. Plan-checkers will not accept the substitution unless you submit a listed assembly from an ICC-ES, UL, or GA-600 listing that explicitly approves it. In practice, just order the correct board. Type X 5/8-inch is a standard SKU at every lumber yard; there's no significant cost premium that justifies the plan-check fight.
What counts as a habitable room above the garage?
Under the CRC, habitable rooms are spaces used for living, sleeping, eating, or cooking. That covers bedrooms, living rooms, family rooms, home offices, and dining rooms. Storage rooms, bathrooms, and mechanical rooms are not habitable, but under the 2025 CRC that distinction does not decide the ceiling: Table R302.6 requires 5/8-inch Type X below any portion of the dwelling unit above the garage. If any part of the dwelling sits over the garage, call out 5/8-inch Type X on the garage ceiling below it. The cost of upgrading a few sheets of drywall is far less than the delay of a follow-up correction.
Do recessed lights in the garage ceiling still comply with R302.6?
Recessed lights can work, but each fixture creates a penetration through the fire-separation assembly. You need IC-rated, airtight fixtures, and the penetration itself needs to be protected per R302.5.3 with an approved material under R302.11, Item 4. A listed recessed light cover is one clean way to do that. Show the fixture type and firestop method on the electrical sheet or the ceiling detail. Standard IC-rated fixtures alone are not enough — they address insulation contact but not fire separation. A callout on the reflected ceiling plan or electrical schedule saves the follow-up correction.
If I'm converting a garage to an ADU, what changes for R302.6?
When the garage becomes the ADU, the separation requirements shift. The wall between the new ADU and any remaining garage space now needs to satisfy R302.6 — and so does the shared wall with the main dwelling if it's an attached conversion. You'll need to document the existing drywall or frame out new walls with the correct board. If there's no garage remaining after conversion, R302.6 may no longer apply to that wall depending on what the adjacent space becomes. Have your plans clearly show each space after conversion, and call out all separation assemblies explicitly. Plan-checkers reviewing ADU conversions look hard at this section.

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