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Home / Code Guides / Shower Size

Minimum Shower Size Code — 900 Square Inches and the 30-Inch Circle

The code’s minimum shower is defined by geometry: 900 square inches of interior cross-section that can swallow a 30-inch circle, held all the way up to 70 inches above the drain. Everything else is valves and waterproofing.

RequirementModel Code StandardSection
Minimum area900 sq in. of interior cross-sectional area, maintained to a height of 70 in. above the drainIRC P2708.1
The circle testThe compartment must be capable of encompassing a 30 in. diameter circle at the required heightIRC P2708.1
Access openingMinimum 22 in. clear access opening; hinged doors swing outward or both waysIRC P2708.1, R307.2
Anti-scald valveIndividual control valves of the pressure-balance, thermostatic, or combination type, set to a maximum 120°F outletIRC P2708.4
Receptor & wallsWaterproof wall finish to 6 ft above the floor; site-built pans lined and sloped 1/4 in. per ft to the drainIRC R307.2, P2709
GlazingAny glass in or facing the compartment within 60 in. of the drain must be temperedIRC R308.4.5

Worth knowing

  • A 30×30 stall passes only if nothing intrudes — a grab bar, curb overhang or valve handle inside the circle can technically fail it; 32×32 is the practical floor.
  • The tile-ready foam pan still needs the slope and flood test most jurisdictions require for site-built receptors — keep the manufacturer instructions on site.
  • Curbless showers are fully code-legal; the design problem is keeping the 1/4 in./ft slope inside the pan without flooding the bathroom — linear drains earn their price here.
  • The 120°F limit is set at the valve, not the water heater — the heater can store hotter for capacity and legionella control while the valve tempers delivery.
Sections cite the 2021 International Residential Code and 2023 National Electrical Code as model standards. This is BuildSpec’s own summary — not ICC or NFPA text; read the authoritative language at codes.iccsafe.org. Your state may be on a different edition with amendments — check your jurisdiction page or get an Address Report.
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