How Much Does a Tub to Shower Conversion Cost in San Francisco?

The drain is the part nobody mentions

Here’s the thing that separates a real conversion quote from a one-day-install brochure. A bathtub drains through a 1½-inch waste line. Under the California Plumbing Code, a shower drain outlet has to be not less than 2 inches in diameter. So a tub to shower conversion is not a fixture swap. It’s a drain replacement with a fixture on top.

In a pre-war San Francisco home that means opening the floor, and often the ceiling below, to get at a cast iron waste line that’s been in place since the building went up. Whether your joists have the depth to accept a 2-inch trap and the fall it needs is the single biggest variable in the whole job — bigger than tile choice, bigger than glass.

It matters twice as much if you want curbless. A zero-threshold shower needs the pan recessed below the surrounding floor, or a linear drain set at the wall with the slope built into a shallower assembly. Both need room in the floor structure that a 1920s Edwardian in the Inner Richmond does not automatically have. Sometimes the answer is a low-profile threshold instead of a true curbless entry, and an honest contractor tells you that at the measuring stage rather than mid-demolition.

This is also why the national one-day-install franchises quote so fast and so cheap. Dropping an acrylic surround into an existing footprint over an existing 1½-inch drain avoids all of the above. It is a different product than a code-compliant shower, and in an older San Francisco building the difference shows up in a failed inspection or a ceiling stain downstairs.

Can you convert a tub in a small or older San Francisco bathroom?

Usually yes, and the code is more accommodating here than people expect.

Under CPC 408.6, a shower compartment needs a minimum finished interior of 1,024 square inches and must be capable of encompassing a 30-inch circle, maintained up to 70 inches above the drain. That sounds tight for a small SF bathroom until you read the exception: the minimum area and dimension requirements don’t apply to a shower receptor measuring at least 30 inches by 60 inches.

A standard alcove bathtub is 30 by 60. So the footprint your tub already occupies is, by code, a legitimate shower footprint. That’s the good news, and it’s why same-footprint conversions are the most common job we do in this city.

Where it gets tighter is the door. CPC 408.5 requires a shower door to provide at least a 22-inch clear opening and to swing outward — which in a narrow San Francisco bathroom can put the door swing into the toilet clearance. Fixed glass panels or a door-free walk-in layout often solve it, and that’s a design decision worth making before anything gets demolished.

Walls also need a nonabsorbent surface to 72 inches above the floor, and any glazing within 60 inches of the shower needs to be tempered safety glass.

Building a curbless or accessible walk-in shower

This is the work worth doing properly, and it’s the reason most of our conversion clients call in the first place — someone in the house is finding it harder to step over a tub wall.

A few things we plan around:

Blocking goes in before the tile. Grab bars need solid backing in the wall, and the time to install it is while the studs are open. Adding it later means opening the wall again. We put blocking in even when the client isn’t ready for bars yet, because it costs almost nothing during the rough-in and a great deal afterwards.

Fold-down seats are allowed to protrude. CPC 408.6 specifically permits fold-down seats in accessible shower stalls to intrude into the required 30-inch circle. That’s a useful allowance in a small bathroom, and one a lot of contractors don’t know.

A curbless shower is a wet location. Without a threshold to contain water, the whole area is treated as a wet location under the building, residential, and electrical codes, which changes waterproofing extent and fixture selection. Ideally the waterproofing extends across the entire bathroom floor; at minimum it should run well past the threshold line.

DBI now handles accessibility review in-house. The Department of Building Inspection conducts disabled access review as part of its own plan review, so projects that aren’t managed by Public Works no longer route separately through the Mayor’s Office on Disability.

Converting a jetted or whirlpool “hot tub” style bathtub

A lot of Bay Area homes remodeled in the late eighties and nineties got an oversized jetted tub — the corner unit with the pump and the air jets that nobody has filled in a decade. Converting one of those to a walk-in shower is a different job than converting a standard alcove tub, and usually a better one.

You gain more space, because these tubs are typically far larger than a 30 by 60 footprint. But you’re also dealing with a pump, a dedicated electrical circuit, and the motor access panel the code requires — CPC 402.10 calls for a minimum 12 by 12 inch access to a whirlpool tub motor. All of that gets decommissioned and removed properly, not abandoned in the wall.

Worth being clear on terminology: an outdoor spa or hot tub on a deck is a separate job involving gas, electrical, and sometimes a dedicated water line. That’s a removal, not a conversion. If that’s what you have, call and we’ll scope it as its own project.

Permits, and the SB 407 trigger nobody warns you about

Two things catch San Francisco homeowners out.

First, the permit and who can pull it. San Francisco requires a permit before renovating or replacing bath fixtures, with exemptions listed in SF Building Code Section 106a.2 — and to apply for a kitchen or bath permit online, the contractor must hold a B license and be registered with the City of San Francisco. Plumbing and electrical trade permits are separate and are pulled by the registered licensed subcontractors, applied for in person, or handled as part of an over-the-counter interior remodel permit. Ask any contractor bidding your job which permits they are pulling and under which license. It’s a fair question and the answer tells you a lot.

Second, SB 407. Under California Civil Code sections 1101.1 through 1101.8, any residential property built and available for use on or before January 1, 1994 must have its non-compliant plumbing fixtures replaced with water-conserving fixtures when the property undergoes alterations or improvements. Read that again with San Francisco’s housing stock in mind — the overwhelming majority of homes in this city predate 1994. A bathroom conversion can therefore trigger fixture compliance beyond the bathroom you’re actually remodeling. It is not usually expensive. It is extremely annoying to discover at final inspection.

While we’re on water: California caps showerheads at 1.8 gallons per minute at 80 psi, and where multiple heads serve one compartment the combined flow can’t exceed that unless the shower is designed so only one outlet runs at a time. If you’re picturing a rain head plus a handheld running together, that’s the constraint to design around. Bathroom remodels also require an exhaust fan of at least 50 CFM ducted to the exterior, switched separately from the lighting.

Is it worth converting a tub to a shower?

For most households, yes — and the resale worry is usually overstated, with one real exception.

Removing your only bathtub in a two-or-more-bedroom family home is the case where agents genuinely push back, because a slice of buyers with small children screen for a tub. If you have a second full bathroom with a tub, that objection largely disappears. In a one-bathroom flat or a condo aimed at professionals or downsizers, a well-built walk-in shower frequently shows better than a tired tub surround.

The stronger argument is the one that isn’t about resale at all. Stepping over a 15-inch tub wall onto a wet surface is how a large share of household bathroom injuries happen, and an accessible shower with proper blocking and a slip-resistant floor lets someone stay in their home considerably longer. Weigh that against a hypothetical future buyer’s preference.

If you’re undecided, get the measurement done first. Whether a true curbless build is even feasible in your floor structure often settles the question on its own.