Shower Enclosure Size Requirement

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Brant Blower

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Berkeley, Ca.
Greetings. We’re looking to install a glass shower enclosure in a corner in a guest bath in a California. The existing space we have to work with is ‘very’ tight in all directions (see attached plan). When I Google the minimum allowed size, most of the home improvement websites cite 30” x 30” min. with a min. 900 square inch area curb to curb. The actual California Plumbing Code (section 408.6) indicates that you’re allowed to have ‘one’ dimension be as tight as 30” but the overall required space needs to be a min. of 1,024 square inches. This means that the other dimension needs to be a hair over 34”, or if we’re applying equal dimensions, needs to be 32 x 32 to get to 1,024 sq. in.

Note that we considered going with a longer shower that butts into the back of the coat closet but trying to avoid having to furr out the left wall and replace the bathroom entrance with a narrower door.

Three questions.

1). Assuming the 1,024 sq. in.. is correct and the 900 sq. in. is incorrect?

2). The code says the measurement is to be taken from ‘top of threshold.’ Does that mean top of curb? In other words, can the measurement be taken from glass to wall instead of inside of curb?

3). Wishful thinking, but is there a code exception I’m missing that allows shower curbs (not enclosure wall) in encroach into the 15” min. clearance from the centerline of the toilet?

Thank you so much in advance!


  • Shwr Plan 21_07.04.pdf
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In the Trades
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Berkeley, CA
1) Yes for California, as you noted.

2) If your curb is the same height at the entrance as under the glass walls, then yes, at the top of the curb. The threshold would the highest point you have to step over to enter the shower.

3) The operative language is here, "15 inches (381 mm) from its center to a side wall or obstruction":

This one seems open to interpretation, but I think you can make a strong case that the side wall is the shower glass, and that the curb is low enough that it is not an obstruction. But if a zealous inspector judged the curb to be an obstruction, it would be hard to say they are wrong.

BTW, have you considered moving or extending the shower to the other corner, so that the shower entrance, lavatory, and WC all share the same "landing" or entrance space? Not sure if that would make the room feel cramped, but it would be the way to minimize the total area required (although the area in the corner between the WC and shower might not be useful for anything else.)

Chers, Wayne
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