A detached garage within 3 feet of the house still needs gypsum

Here's the thing: on a residential plan set, "detached garage" gets read as "exempt from the dwelling–garage separation." Draw it three feet off the house, call it a separate structure, skip the gypsum note. That reading skips a row of Table R302.6 that doesn't care whether the garage is attached.

What Table R302.6 actually says

Section R302.6 — "Dwelling unit garage and/or carport fire separation" — sends you to Table R302.6 for the material and where it goes. Most people can recite the first two rows from memory:

• From the dwelling unit and attics: not less than 1/2-inch gypsum board or equivalent, applied to the garage side.
• From portions of the dwelling unit above the garage or carport: not less than 5/8-inch Type X gypsum board or equivalent.

Those are the attached-garage answers — the shared wall, and the ceiling when there's habitable space on top. There's a third row for the structure supporting a floor/ceiling assembly used as the separation (1/2-inch again). And then there's the row nobody quotes.

Proximity is the trigger, not attachment

The fourth row:

• Garages located less than 3 feet from a dwelling unit on the same lot: not less than 1/2-inch gypsum board or equivalent, applied to the interior side of exterior walls that are within this area.

Read that trigger again. It's distance, not attachment. A freestanding garage — including the garage portion of a garage-containing ADU — set less than 3 feet from a dwelling on the same lot lands in this row exactly the same as if it shared a wall. "Detached" buys you nothing here. And the number isn't generous: it's a hard 3 feet, measured to the dwelling unit, same lot.

Verified against the 2025 California Residential Code (with January 2026 Errata): Table R302.6's fourth separation row reads — "Garages located less than 3 feet from a dwelling unit on the same lot: Not less than 1/2-inch gypsum board or equivalent applied to the interior side of exterior walls that are within this area."

Which walls actually owe gypsum

Two details in that row decide the scope, and both get missed.

First, it's the interior side of exterior walls — the inside face of the garage's own exterior walls, the cavity side, not the weather side. This is fire protection for the garage looking out toward the house, applied where you'd hang drywall anyway.

Second, it's only the walls within this area — the part of the garage that falls inside the 3-foot band facing the dwelling. R302.6 also carves out orientation: the table's wall-separation provisions "shall not apply to garage walls that are perpendicular to the adjacent dwelling unit wall." So the row reaches the exterior wall that faces the house and sits inside 3 feet — not the walls running away from it.

One more note for the detail: R302.6 says gypsum attachment shall comply with Table R702.3.5. This isn't a decorative skim coat — fasten it like the rated separation it's standing in for.

Before you assume the table doesn't apply

Measure the gap first. The failure mode is uniform: a detached garage — or the garage in a garage-containing ADU — drawn just off the house, no separation note, because the designer treated "detached" as "exempt." If the clear distance to the dwelling is anything under 3 feet on the same lot, the facing exterior wall owes 1/2-inch gypsum on the interior, and a plan checker who knows the row will red-line its absence.

Where the geometry is close — a garage at 3 feet 1 inch, an irregular footprint, an ADU that's part garage — how the gap is measured and which walls count as "within this area" can come down to interpretation. Verify with your local jurisdiction before you finalize, and get the reviewer's read on paper. This is a code-scope question, not legal advice.

What CrossBeam does with it

CrossBeam reads the whole separation table, not just the two rows everyone remembers — so when a detached garage — or the garage portion of an ADU — sits inside 3 feet of the dwelling, it flags the missing interior gypsum before the correction letter does. You get the row, the measurement that triggered it, and the walls it touches, tied to the sheet.