A bathroom remodel permit doesn't stop at the bathroom door. If your California house was built on or before January 1, 1994, the city won't give final approval until, with narrow exceptions, every toilet, showerhead and faucet in it that's over the old water limits has been replaced [1][2][3]. The permit also brings smoke alarms up to new-home locations throughout the house [4].
The fixture swap isn't new, either: the same law told owners to make it by January 1, 2017, permit or not, and a seller must tell a buyer in writing about that rule and whether any old fixtures are left [2]. The permit is where the city checks.
Under the state's residential code, painting, tiling, cabinets, countertops and similar finish work need no building permit [5]. Menlo Park's version says "tiling except in showers," so retiling a shower there needs a permit [6].
Take an example: a 1960s Peninsula ranch with two bathrooms, gas heat and an attached garage. The owners want to redo the hall bath and nothing else.
Does a bathroom permit mean replacing old high-flow fixtures house-wide?
In a house built and available for use on or before January 1, 1994, it does, with narrow exceptions: California's fixture law, SB 407, covers those homes [1]. In a single-family home, any alteration or improvement brings it in. Before final approval, the permit applicant must replace every "noncompliant" fixture in the house [2]:
a toilet built to use more than 1.6 gallons a flush;
a showerhead built to flow more than 2.5 gallons a minute;
any indoor faucet that lets out more than 2.2 gallons a minute [3].
Fixtures at or under those numbers can stay [3]. Replacements must meet today's new-home standard [3]. In the 2025 plumbing code, that's 1.28 gallons a flush for toilets, 1.8 gallons a minute for showerheads, 1.2 for bathroom faucets, and 1.8 for kitchen faucets, with a short boost to 2.2 allowed [7].
So the primary bath and the kitchen are in scope, though nobody is working there.
The exceptions that could fit a lived-in house are narrow: a registered historical site, or a licensed plumber's certification that the swap isn't technically feasible [8]. Where a city or county adopted its own retrofit ordinance before July 1, 2009 and it's still in effect, that ordinance applies instead [9].
Does a bathroom remodel mean smoke and CO alarms throughout the house?
Any alteration that needs a permit means the whole house gets smoke alarms where a new home would have them, including each bedroom, outside the bedrooms and each additional story [4]. Whether alarms must be wired in or can run on batteries depends on what the work opens up, and on whether an attic, crawl space or basement gives a way to run wire [4]. On permits for work over $1,000, the city won't sign off until every required smoke alarm is listed by the State Fire Marshal [10].
A house with a heater or appliance that burns gas or another fossil fuel, a fireplace or an attached garage has needed carbon monoxide alarms since July 1, 2011, permit or not [11]. The example ranch qualifies twice, so CO alarms belong outside the bedrooms and on every level [11][12].
Ask whether a bid covers the whole house
A bid that prices only the hall bath can grow at final. If your house was built by January 1, 1994, a complete one also lists the failing fixtures elsewhere and the alarms the house still needs.
Minimum shower size, door width and the flood test
News · January 1, 2026 · California's 2025 Building Standards Code, including its residential, plumbing, electrical and energy codes, took effect January 1, 2026. [13]
The 2025 California Plumbing Code sets the basics for a new shower [7]:
an inside area of at least 1,024 square inches that can hold a 30-inch circle (a pan at least 30 by 60 inches is exempt);
a door that opens to leave at least 22 inches clear;
for a pan built on site, a waterproof liner that turns up at least 3 inches above the curb, and a flood test with at least 2 inches of water for at least 15 minutes, using a temporary 2-inch dam if there's no curb.
Fifteen minutes is the code's minimum; a longer test is allowed [7], so ask each bidder how long theirs will run.
Glass in walls or enclosures next to a tub or shower must be safety glass that passes the code's impact test when its bottom edge is less than 60 inches above a surface you stand or walk on, unless it sits more than 60 inches sideways from the tub's water edge or the shower's edge [14].
Does a bathroom need an exhaust fan and GFCI protection?
The residential code says a bathroom with a tub or shower must have mechanical ventilation for humidity control, and an opening window doesn't count [15]. San Mateo's 2020 guide says a 50 cfm fan is required in all bathroom remodels unless the existing ceiling stays in place, even with an operable window [16].
When the remodel installs a new bath fan or alters the old one, California's Energy Code applies the new-home rule: at least 50 cubic feet per minute from a fan that runs as needed, or 20 from one that runs nonstop [17]. The installer has to verify the airflow, by measuring it or by building to the code's duct table [17]. So swapping the fan brings the rule even where the ceiling stays [16][17].
Under the 2025 California Electrical Code [18], bathroom receptacles rated 125 to 250 volts need ground-fault (GFCI) protection, with narrow exceptions such as a receptacle built into a bath exhaust fan [19]. Arc-fault (AFCI) protection is different. Bathrooms aren't on the code's list of rooms that need it, though hallways and bedrooms are, and if the work changes a circuit that also serves them, that circuit needs AFCI too, unless the change is only an extension of 6 feet or less with no new outlets or devices [18].
Do you need lead or asbestos testing before a bathroom remodel?
A 1960s family house is "target housing" under EPA's lead rule, which covers most housing built before 1978 [20]. Paid renovation there must be done by a certified firm using certified renovators, unless testing under the rule shows the painted parts being disturbed are free of lead-based paint [21]. Tearing out painted walls doesn't qualify for the rule's small-job exemption [21]. From July 1, 2027, the firm and at least one of its people on site also need a California certificate for paid work that will disturb lead-based or presumed lead-based paint [22].
For asbestos, the Bay Area Air District requires no full survey in a house with four or fewer units. But the material must be sampled and tested before anyone removes or disturbs heating, ventilation or air-conditioning ducts and systems, acoustic ceiling material, such as a popcorn ceiling, or acoustic plaster, textured or skim-coated walls, cement siding or stucco, or resilient flooring such as vinyl [23]. Instead of testing, an owner can treat the material as asbestos and have it handled under the district's removal rules [23].
Ceramic tile isn't on that list, so the Air District rule doesn't require sampling the tile itself. Textured or skim-coated walls around it, a vinyl floor or an old fan duct would [23].
Bathroom permit fees, review and sewer checks in four Peninsula cities
San Mateo. The fee schedule for July 2026 to June 2027 lists $719.58 for each combination building, plumbing, electrical and mechanical permit for a bathroom or kitchen remodel, under minor residential remodels, plus fees and taxes figured from the job's valuation, such as a 0.59% general plan maintenance fee [24]. A bathroom remodel with conventional wall changes, no structural calculations and no fire review can get over-the-counter review, in person or virtual, unless one of the city's full-review conditions applies, such as an open code-enforcement case, zoning or right-of-way impacts, or a review the plan checker expects to take more than 30 minutes (list revised November 14, 2025) [25].
Hillsborough.
News · May 11, 2026 · Hillsborough's FY 2026-27 fee schedule, adopted May 11, 2026, sets $1,326 per permit for like-for-like kitchen or bathroom work with no wall changes, before other fees and taxes. [26]
The council adopted the fees unanimously [27]. Before then, the base fee was valuation-based, and the same row now lists $261 for "Each Additional," without saying what is counted [26].
Sewer laterals. The lateral is the pipe from the house to the public sewer [28]. Four cities tie it to remodel permits:
In San Carlos, a remodel that adds even one toilet counts as a "building improvement," and its permit application triggers a camera inspection of the lateral, unless a valid compliance certificate is on file [29]. So do remodels of over 25 percent of the building or above a cost threshold the council can adjust [29].
San Mateo requires an inspection before the building permit is issued for remodels costing more than $90,000 (a threshold set in 2020), unless the lateral was inspected in the past 5 years with any required repairs done, was fully replaced under a city permit in the past 25, or the Public Works Director approves another exemption [30][28].
Belmont requires a valid sewer lateral certificate before the final for improvements the building official values at $200,000 or more [31].
In Hillsborough, when more than 1,500 square feet of an existing house is remodeled, the lateral is evaluated and must be repaired or replaced if necessary [32].
Before you ask for bids
Find the year built. On or before January 1, 1994 brings the fixture rule; built before 1978 usually brings the lead rule.
Walk every room. List each toilet, showerhead and faucet, and every smoke and CO alarm, not just the ones in the bathroom.
Ask the city which permit applies, what it costs, and whether the job triggers a sewer lateral inspection.
Ask each bidder to price the fixtures and alarms outside the bathroom and the lead and asbestos steps.
Amiari Construction remodels bathrooms on the Peninsula.
How we checked this: In October 2026, Amiari Construction read the state laws in the Legislature's own records, the 2025 California codes (official texts, except the electrical code's GFCI rule, which we read in a trade book's summary because the official copy requires a sign-in), EPA and Air District rules, and five cities' codes and fees.
