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Building Code Reference

Got a CRC R318.6 correction?

Hallway minimum width

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 R318.6 requires hallways in California residential buildings to maintain a minimum 36-inch clear width, measured between finished wall surfaces. That 36 inches is the finished dimension, not the stud-to-stud rough opening, so drywall thickness eats into that number. Single-family homes, ADUs, and multi-unit residential projects all fall under this section, and it's one of the first things a plan-checker measures when reviewing floor plans.

How to fix it

  1. Dimension every hallway on the floor plan

    Add an explicit dimension callout to each hallway on the floor plan, labeled as 'clear width (finished)'. Do not rely on the plan-checker scaling from grid lines or inferring from room dimensions. The callout should read something like '36" min clear (finished)', placed inside the hallway corridor on the plan sheet. If you have multiple hallways, every one needs its own callout. A single note in the general notes saying 'all hallways minimum 36 inches' is not enough; plan-checkers want to see each corridor individually dimensioned so they can confirm compliance without doing the math themselves.

  2. Verify the 36 inches is measured from finished surfaces

    Measure from finish surface to finish surface, not stud face to stud face. With 5/8-inch Type X drywall on each side, you need a minimum 37-1/4-inch stud-to-stud rough opening to hit 36 inches clear. With standard 1/2-inch drywall on each side, the minimum rough opening is 37 inches. If walls have tile, paneling, or furring strips, account for those added thicknesses. Write the finished dimension on the plan, not the framed dimension. If your drafter or designer is pulling dimensions from the framing plan, check the math before submitting.

  3. Measure existing hallways before submitting a remodel

    If your permit involves work anywhere near an existing hallway, measure the existing clear width before submitting. Bring a tape measure on site and record the actual finished dimension. If the existing hall is under 36 inches, check with your building department whether the upgrade is required as a condition of the remodel permit. Different cities apply different triggers. Flagging it yourself in the application, with a note about the existing non-conforming width and your remediation plan, is faster than receiving a correction letter after the city has already reviewed your plans. It also shows the plan-checker you know what you're doing.

  4. Coordinate hallway widths across all plan sheets

    The floor plan, the reflected ceiling plan, the framing plan, and any interior elevation sheets should all show consistent hallway widths. If the floor plan shows 36 inches and the framing plan shows 37 inches stud-to-stud, the plan-checker has to stop and figure out whether the discrepancy means a problem or just poor coordination. Either way, they'll write a correction asking you to reconcile the sheets. Run a cross-check before submitting: open each plan sheet, find every corridor, and confirm the dimension callouts agree.

  5. Note projections into the hallway path

    Door casing, baseboard, radiators, electrical panels, and plumbing cleanout covers all project into the hallway. The 36-inch clear width calculation is measured wall surface to wall surface, so a flush-mounted electrical panel recessed into the wall does not count against you, but a surface-mounted panel that projects 4 inches into the hallway does. Note any significant projections in your plan notes. If a door swings into the hallway, the door swing arc can create a pinch point during egress. Your plan notes should confirm the clear path is maintained even with the door at its maximum swing.

  6. Add a cross-section detail for corridors at or near the minimum

    If your hallway is at exactly 36 inches clear or within 1/4 inch of the minimum, include a cross-section detail at 1/4"=1' scale showing the stud-to-stud dimension, the finish material and thickness on each side, and the resulting clear width with a calculation. Something like: 'Rough opening: 37-1/4". Finish each side: 5/8" Type X GWB. Clear width: 37-1/4" - (2 x 5/8") = 36". Code minimum: 36". Compliant.' This detail takes five minutes to draw and typically eliminates the back-and-forth on tight corridors.

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Why you got flagged

The most common reason for a correction on R318.6 is that the hallway dimensions shown on the floor plan are stud-to-stud, not finished-surface-to-finished-surface. A hallway framed at 38 inches on center sounds like plenty of room until 5/8-inch drywall goes on each side, dropping the clear width to 36-3/4 inches. That's still compliant, but if the framing was 37 inches o.c., the finished width is 35-3/4 inches and the plan-checker will flag it.

A second scenario shows up in ADU projects. Builders add a hallway to connect a new bedroom or bathroom, and the new corridor gets squeezed by existing framing, a plumbing chase, or a bearing wall that can't move. The hallway as drawn on the plan measures 36 inches from finish to finish, but when the plan-checker scales it against the floor plan dimensions, they find it's actually 34 or 35 inches. The note that says "hallway per code" without a callout dimension is a near-automatic correction.

Remodels and additions are a third situation. When a contractor submits a remodel that routes through an existing hallway, the plan-checker checks whether that existing hallway meets current code. If the existing hall is 32 or 34 inches wide, it was probably legal under an older code edition, but the remodel can trigger an upgrade requirement. This surprises contractors who didn't expect the plan check to loop back to existing conditions.

Plans that show correct dimensions on one sheet but inconsistent dimensions on another also get flagged. If the floor plan shows a 36-inch hallway but the reflected ceiling plan or interior elevations show a different width, the plan-checker will call it out and ask for coordination.

The official code

California Residential Code Part 2.5 — Building Standards Commission

Read the source →

Common questions

Is CRC R318.6 the 36-inch hallway rule for residential?
Yes. CRC R318.6 sets the minimum clear width for hallways in California residential construction at 36 inches, measured between finished wall surfaces. This applies to new construction and to hallways in the scope of work for additions and major remodels. The 36-inch number is not a suggestion or a typical practice, it is the code floor. If your hallway comes in at 35-3/4 inches, you have a correction and will need to revise and resubmit.
Does the 36-inch hallway minimum apply to ADUs?
Yes. ADUs are residential occupancies and fall under the California Residential Code. CRC R318.6 applies to the hallways within an ADU the same way it applies to a primary dwelling. If you are adding an ADU to an existing single-family lot and the new ADU has a connecting corridor or internal hallway, that corridor must be at least 36 inches clear between finished surfaces. The ADU's size or whether it's attached or detached doesn't change the hallway requirement.
What counts toward the 36 inches, studs or drywall?
Finished surfaces count. The 36-inch clear width is measured between the surfaces that a person actually walks past, not the stud faces. Drywall, tile, paneling, and any other wall finish materials reduce the clear width from the rough-framed opening. With standard 5/8-inch Type X drywall on each side, your stud-to-stud rough opening needs to be at least 37-1/4 inches to hit 36 inches clear. With 1/2-inch drywall, the minimum rough opening is 37 inches. If you spec thicker finishes on either wall, add that thickness to your minimum rough-opening calculation.
Can a door opening in the hallway count toward the 36-inch width?
No. The 36-inch minimum is the clear width of the hallway passage itself, measured at the narrowest point between wall surfaces. A door opening within the hallway is governed by its own requirements (CRC R318.2 covers minimum door widths for egress). What can affect the corridor width is the door frame and casing that projects out from the wall. If the door frame and casing project 1 inch into the hallway on each side, the 36-inch corridor effectively becomes 34 inches at that point during door use. Make sure your casings don't create a pinch point below the 36-inch minimum.
My remodel doesn't touch the hallway. Do I still have to upgrade it to 36 inches?
It depends on the scope and how your jurisdiction interprets it. In many California cities, a remodel permit that affects the area adjacent to an existing non-conforming hallway can trigger an upgrade requirement. The plan-checker has discretion. The safest approach: measure the existing hallway before you submit and note its width in your permit application. If it's under 36 inches, call or email the building department and ask whether the upgrade is required before you finalize your plans. Getting that answer in writing saves you a correction round later.
Does R318.6 apply to commercial projects or just residential?
CRC R318.6 is California Residential Code, so it covers residential occupancies under the CRC, primarily one- and two-family dwellings and townhouses up to three stories. Commercial buildings, multifamily buildings over three stories, and other occupancy types fall under the California Building Code (CBC), which has its own corridor width requirements in different sections. If you're working on a project that might be classified under the CBC rather than the CRC, check with your building department which code set applies before you dimension your corridors.

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