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Building Code Reference

Got a CPC 408.7 correction?

Shower minimum size

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

CPC 408.7 sets the minimum interior size for a shower compartment in California. The compartment must have at least 1,024 square inches of floor area, must encompass a circle at least 30 inches in diameter, and must maintain that clearance from the drain up to 70 inches above it. Shower surrounds, curbs, finished thresholds, and projections other than valves, showerheads, soap dishes, shelves, and grab bars all count against those minimums. Bathroom remodels, ADUs, and new single-family permits get flagged on 408.7 most often when the plans skip the shower dimensions entirely or when a tiled threshold or built-in bench intrudes into the required area.

How to fix it

  1. Dimension the finished interior floor area on the plan

    Add explicit width and depth dimensions to your shower on the bathroom floor plan, referencing finished surfaces, not framing. Show the net interior area in square inches (or show both dimensions so the plan-checker can calculate: e.g., 36 in x 36 in = 1,296 sq in). If the stall is non-rectangular, show the square footage with a note and a detail.

  2. Confirm and annotate the 30-inch inscribed circle

    Draw or note a 30-inch circle that fits entirely within the finished interior floor area of the shower, not overlapping the threshold, curb, or any projecting fixture. For standard 36 x 36 or 36 x 48 stalls this is straightforward. For neo-angle or curved stalls, draw the circle on the detail sheet so the plan-checker can verify it fits without scaling the drawing.

  3. Check the 70-inch clearance height above the drain

    Measure from the finished drain elevation up to the lowest point above the minimum floor area. This includes the underside of any soffit, chase, dropped ceiling, header, or sloped ceiling plane that falls within the required footprint. If anything drops below 70 inches, you either need to raise it or reduce the area it covers so it falls outside the required circle. Note the clearance on your elevation or section sheet.

  4. Account for curbs, thresholds, and niches

    A curb or threshold at the entry, if it projects inward, reduces the usable interior area. Show curb thickness on the plan or detail and verify the remaining interior still meets 1,024 sq in. Same rule for built-in seats or benches that extend into the minimum floor area at any height below 70 inches above the drain. A recessed niche does not protrude, and soap dishes and shelves are permitted protrusions, but a built-in bench is not, so you may need to relocate or resize it.

  5. Add a shower size compliance note to the plans

    In your general notes or on the bathroom plan sheet, add a code compliance note such as: "Shower compartment per CPC 408.7: minimum 1,024 sq in interior area, 30-inch minimum inscribed circle, 70-inch minimum clearance above drain." This signals to the plan-checker that you have read the code and have deliberately dimensioned to meet it. Notes like this reduce back-and-forth significantly on first-round reviews.

  6. Verify fixture clearances do not count against the area

    The code lets fixture valves, showerheads, soap dishes, shelves, and safety grab bars or rails protrude into the required area below 70 inches. Other projections below 70 inches count against it and should be shown on the plan. Fold-down seats in accessible showers may protrude into the 30-inch circle, but a built-in bench needs careful placement.

  7. Resubmit with a marked-up response to the correction

    On your correction-response sheet, call out the specific plan sheet and detail where the shower size is now documented. Reference CPC 408.7 directly in your response. Plan-checkers review dozens of projects; the easier you make it to find the answer, the faster the approval. A clouded revision bubble on the floor plan plus a note in your response cover sheet is the fastest path through a resubmit.

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Why you got flagged

Here is why plan-checkers flag CPC 408.7 on corrections letters.

The most common trigger is missing dimensions on the plans. A bathroom floor plan that shows a shower stall without calling out the interior width, depth, or the inscribed-circle dimension gives the plan-checker nothing to approve. They have to assume the worst and flag it. This happens constantly on remodels where the architect or drafter figures the tile contractor will handle sizing in the field.

The second scenario is a finished-dimension trap. The plans show a 32 x 32-inch framed opening, which looks fine on paper, but once you account for the tile substrate, tile, and a threshold or curb, the finished interior area falls below 1,024 square inches. The code measures interior area after finishes, so the framing dimensions are not what matters. If the plans show rough framing but not finished dimensions, expect a correction.

A third flag comes from oddly shaped stalls. Neo-angle, corner-entry, and custom walk-in configurations sometimes pass the square-footage test on a rectangle assumption but fail the inscribed-30-inch-circle requirement. A narrow L-shaped shower can easily have more than 1,024 square inches of area while still being too tight for a person to turn around. Plan-checkers will specifically ask for a note or detail showing the 30-inch circle fits.

Finally, the 70-inch height requirement catches remodels where a low header, a ceiling joist, or a soffit cuts across the shower above drain height. If any obstruction within the minimum floor area drops below 70 inches above the drain, the compartment does not comply.

The official code

2025 California Plumbing Code (Title 24, Part 5), Section 408.7 Shower Compartments, via California Building Standards Commission

Read the source →

Common questions

Does a 32 x 32 inch shower meet CPC 408.7?
A 32 x 32 inch stall gives you 1,024 square inches exactly, which hits the minimum floor area. But that measurement has to be the finished interior dimension after tile, substrate, and any curb. If the framing is 32 x 32 and the tile and backer board eat into that, the finished interior drops below 1,024 sq in and it fails. A safer target is 36 x 36 finished, which gives you 1,296 sq in and leaves room for normal finish thickness. Also confirm a 30-inch circle fits inside the finished stall.
What counts as interior area under CPC 408.7?
The interior area is the usable floor space inside the finished shower compartment, measured at a height equal to the top of the threshold. Curbs and thresholds that project inward, built-in seats below 70 inches above the drain, and any other projections that reduce the usable space all shrink the count. Valves, showerheads, soap dishes, shelves, and grab bars are permitted protrusions and do not reduce the minimum area. The one seat the code lets protrude into the 30-inch circle is a fold-down seat in an accessible shower. A fixed bench is not on the permitted list, so it reduces the area.
Why does the shower need to fit a 30-inch circle if the area is already over 1,024 sq in?
Area alone does not guarantee a usable shower. A stall could be 20 inches wide and 52 inches long, which is just over 1,024 sq in, but nobody can turn around in it. The 30-inch inscribed circle requirement ensures the compartment is proportioned for actual use. Both requirements must be met simultaneously: the area must hit 1,024 sq in AND a 30-inch circle must fit inside the finished floor area. The code exempts showers designed to CBC Chapter 11A and shower receptors at least 30 inches wide and 60 inches long. A neo-angle or L-shaped stall can fail the circle test even while passing the area test.
Does CPC 408.7 apply to a bathroom remodel or just new construction?
It applies to both. Any permit that includes shower work, whether a full bathroom remodel, an ADU build-out, or a new single-family home, triggers 408.7. The code does not carve out existing showers from the requirement when they are part of a permitted scope. If you are just re-tiling an existing shower without changing the layout or dimensions, many jurisdictions treat that as maintenance and do not require a full CPC 408.7 review. But any structural change, plumbing rough-in, or change to the shower footprint brings the minimum-size requirement into play.
Does the shower pan or base count toward the 1,024 sq in?
The usable floor area inside the shower, including the shower pan or the tiled floor, is what gets measured. The pan itself is part of the compartment. What the code is looking at is the open, usable floor area once everything is built, not the raw pan dimensions. Prefab shower pans are typically labeled by their nominal framing size, not the finished interior, so check the actual interior dimension of the pan you are specifying and confirm it leaves enough room after the surround panels are installed.
Can a shower door or glass enclosure reduce the 30-inch circle clearance?
A hinged shower door that swings inward will reduce the usable floor area when the door is open. The code also requires shower doors to open so as to maintain at least a 22-inch unobstructed opening for egress (CPC 408.6), so an inward swing that blocks the entry is a problem. Sliding doors and hinged doors that swing outward do not reduce the interior footprint. Frameless glass panels that are fixed do not reduce area. When in doubt, show the door swing on the floor plan so the plan-checker can verify.
What if the existing shower is undersized and I am not changing it?
If the permitted scope does not include the shower, an existing undersized shower generally does not get flagged under CPC 408.7 during plan review. Plan-checkers review the work on the permit, not every existing condition in the house. However, if the inspector notes it during rough inspection and flags it as a code violation, that is a separate matter. If your remodel scope goes near the shower, even for adjacent plumbing or tile work, expect the plan-checker to ask you to document the shower dimensions anyway.

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