Curbless Showers: What It Takes to Build a Zero-Threshold Shower in a Bay Area Home
A curbless shower, also called a zero-threshold or walk-in shower, has no step or curb at the entry. The bathroom floor simply continues into the shower. It's a beautiful look, and it's one of the best things you can do if you plan to stay in your home as you get older.
It's also one of the more technical tile projects, because the water has to go to the drain without a curb to hold it back. Here's what goes into getting it right.
Why homeowners choose curbless
Easier access for anyone with mobility concerns, now or later, and no curb to trip over
A bigger, more open look, especially in a small bathroom
Continuous tile from the bathroom floor into the shower
Easier cleaning, with no curb edges to scrub
The rules: what Bay Area cities look for
Requirements vary by city, so always confirm with your building department. Two published examples give a good picture:
Albany's curbless shower guidelines list specific numbers (City of Albany):
The finished threshold can be at most ½ inch above the bathroom floor, with any change over ¼ inch beveled.
The shower floor slopes to the drain at ¼ inch to ½ inch per foot.
The waterproof liner extends at least 12 inches beyond the threshold into the bathroom.
The top of the drain sits at least 2 inches below the top of the finished threshold.
The shower must hold at least 9.6 gallons above the drain without spilling over the threshold.
The shower still needs at least 1,024 square inches of floor and room for a 30-inch circle.
Pleasanton goes further: its bathroom handout says a curbless shower requires waterproofing of the entire room, not just the shower. (City of Pleasanton)
The big question: where does the slope come from?
A normal shower gets its slope by building the floor up inside a curb. Without a curb, the shower floor has to sit lower than the bathroom floor, or the bathroom floor has to come up. There are two main ways to do it:
Recess the floor. The subfloor in the shower area is dropped so the sloped shower floor finishes flush with the bathroom. Floor framing can't simply be cut away, though. It has to be reinforced or reframed properly, and engineered I-joists have their own rules. Weyerhaeuser, for example, warns against damaging the joist flanges and describes approved ways to support a recessed subfloor. (Weyerhaeuser)
Build up the rest of the bathroom. A thin sloped tray sits on the existing subfloor, the bathroom floor is raised slightly with underlayment and membrane to meet it, and a linear drain at the entry catches the water. Fine Homebuilding describes this approach as a way to avoid cutting joists. (Fine Homebuilding)
Which one fits depends on your floor framing, the height of the hallway floor outside the bathroom, and where the drain can go.
Slab floors and Eichlers
Homes built on a concrete slab, including many Bay Area Eichlers, add another layer: recessing the floor means cutting concrete, and many Eichlers have radiant heat tubing in the slab. Mapping that tubing first is essential. See our guide to tile work in Eichler homes.
Condos and 55+ communities
In a condo, or a community like Rossmoor in Walnut Creek, changes to the floor and plumbing usually need HOA or mutual approval before the city permit. Our condo remodel guide covers the approval steps.
Other details worth planning
Linear drains along the entry or back wall let you use large-format tile, since the floor only slopes in one direction.
Slip resistance: smaller tiles with more grout lines, or a textured porcelain, give better footing on a wet floor.
Glass: a fixed panel instead of a door keeps the entry open. Plan the spray direction so water stays in the shower.
Blocking for grab bars inside the walls before tile goes up.
A bench or fold-down seat, with the waterproofing carried over the seat.
What about cost?
Plan on a curbless shower costing more than a standard walk-in shower, because of the floor work, the extra waterproofing and the drain. For typical walk-in shower ranges in the Bay Area, see our tile cost guide and our post on tub-to-shower conversions.
Thinking about a curbless shower?
Send Mike a few photos of your bathroom, including the doorway, and tell him your city and whether the house is on a raised floor or a slab. He'll walk you through which approach fits your home.
Call or text 916-847-2825, or request a free estimate on our website.
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