Thinnest shower wall?

attofaradMarch 19, 2012

I'm really fighting for every fraction of an inch, to get the required minimum shower width (30 inches finished), toilet space, and still fit a 24" vanity with sink centerline 15" from the wall.

What is the minimum distance from stud to surface of tile on the shower walls? What is the construction for that (waterproofing, backer, thinset, tile?) ?

I could go with a tub/shower, which allows a waiver to the 30" minimum finished shower width, but wife doesn't want to

do that.



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Sophie Wheeler

30" is too small for a shower. It won't pass inspection. You need at least 32"(IRC) or 34"(UPC) depending on which code your jurisdiction follows.

For the wall, you need 1/2" backerboard over poly, which doesn't really add to the thickness. Depending on thickness of the tile you pick, the thinset and tile can add another 1/2" to 5/8".

Go with an 18" vanity instead of a 24". It's the only way to get everything in the space that you want.

    Bookmark   March 19, 2012 at 12:19PM
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IRC requires a minimum of 30". You are actually allowed to go down to 25" in one dimension, as long as the total cross-sectional area is at least 1300 sq inches. That might be very uncomfortable, though! You can use very thin tile and get the tile and thinset dimension down to about 1/4". You can turn the framing studs sideways and gain an extra 2" there (but not in the wall with the valve, it won't fit). The width of the shower is measured above the threshold, so if you use a glass wall sitting on top of the threshold, you can gain some extra room.

    Bookmark   March 19, 2012 at 12:59PM
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Thanks hollysprings.

I'll have to check with the inspector here in San Jose, but everything I've read here requires a minimum of 30", with a minimum area of 1024. If it were square, that area would be 32" on a side. With 30" width, the minimum length would be a bit over 34". I have over 60" available in that direction.

It seems that they are perfectly happy for you to install a tub with enclosure, such that the final width tile-to-glass is actually slightly under 30", but if the tub isn't there they want the 30" minimum.

Here is a link that might be useful: Local code, but not my town

    Bookmark   March 19, 2012 at 1:25PM
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IRC minimum rough pan is 32" x 32" REF: IRC 2708.1

But I an only a Master Plumber,,what do I know about these things?

    Bookmark   March 19, 2012 at 1:57PM
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P2708.1 General. Shower compartments shall have at least 900 square inches (0.6 m2) of interior cross-sectional area. Shower compartments shall be not less than 30 inches (762 mm) in minimum dimension measured from the finished interior dimension of the shower compartment, exclusive of fixture valves, shower heads, soap dishes, and safety grab bars or rails. The minimum required area and dimension shall be measured from the finished interior dimension at a height equal to the top of the threshold and at a point tangent to its centerline and shall be continued to a height of not less than 70 inches (1778 mm) above the shower drain outlet. Hinged shower doors shall open outward. The wall area above built-in tubs having installed shower heads and in shower compartments shall be constructed in accordance with Section R702.4. Such walls shall form a water-tight joint with each other and with either the tub, receptor or shower floor.


1. Fold-down seats shall be permitted in the shower, provided the required 900-square-inch (0.6 m2) dimension is maintained when the seat is in the folded-up position.
2. Shower compartments having not less than 25 inches (635 mm) in minimum dimension measured from the finished interior dimension of the compartment provided that the shower compartment has a minimum of 1,300 square inches (0.838 m2) of cross-sectional area.

Copied straight from the code itself. This is for one- and two- family dwellings. Perhaps you are referring to commercial work? Or maybe your local jurisdiction is different.

    Bookmark   March 19, 2012 at 2:50PM
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I found what I think is the California wording, but it may or may not be good for San Jose.

The exception #2 you have isn't there, but we have

"(2) The minimum required area and dimension shall not
apply for a shower receptor having overall dimensions
of not less than thirty (30) inches (762 mm) in width and
sixty (60) inches (1,524 mm) in length."

So I can apparently use a 30 inch receptor, which will end up with about 27.5" tile to glass, or even a 32" can be made to work in my case. I'd rather fab a tile base, but I could deal with this.

    Bookmark   March 19, 2012 at 4:59PM
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You may want to use an electronic mixing valve.which can be mounted remotely (ex the basement or anywhere within 30 feet of the position in the shower where you will be mounting the controller - at least with a Moen) with the controller mounted anywhere that is convenient in the shower (ie the corner). You can then run your plumbing up a 2*3 (Actually 1.5*2.5) stud wall - saving you an inch over std 2*4 studs. I am not an expert, however, I would not try to tile a wall supported by sideways 2*4's under any circumstances. Way too much flex - which will lead to cracked grout lines and/or tiles. Finally - although not asked, I would use hydroban or a topical vapor membrane - I just did a Kerdie shower and I really like it. Good luck.

    Bookmark   March 19, 2012 at 9:14PM
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Treasure, I don't have a very tight constraint on the plumbing end -- I have 68.5" in that direction. Good point about the wall flex.

    Bookmark   March 19, 2012 at 9:33PM
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Use a sheet of tempered glass instead of a stud wall.

Use Kerlite as the thinnest tile.
Behind it, use metal instead of wood studs.
Use 1/8th inch steel flat bar.

    Bookmark   March 20, 2012 at 7:26AM
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