BATHROOM REMODELING IN COSTA MESA, CA

Costa Mesa sorts its permit information by type, so it helps to know which kind of bathroom project you have before you look:

• Finish work, such as paint, a new mirror or towel bars. Ask Building Safety rather than assuming no permit is needed.
• A toilet, faucet or showerhead replaced where it is. Check the Insta-Permit list and ask whether the swap needs a permit.
• A rebuilt shower, a tub-to-shower conversion or a moved drain. The valve, drain, wall and floor all change, so plan on a permit and ask whether it needs plans.
• New electrical work, such as added outlets, a heated floor, new lighting or a circuit for the exhaust fan. Plan on a permit for this work too.

• City of Costa Mesa: Insta-Permit (opens in a new tab)
• City of Costa Mesa: Permit Types & Submittal Requirements (opens in a new tab)
• City of Costa Mesa: Building Permits (opens in a new tab)
• City of Costa Mesa: Plan Check Services (opens in a new tab)
• City of Costa Mesa: Plan Check Submittal Procedure (opens in a new tab)

We have relied on the titles of these city pages, not on their lists. Confirm with Building Safety which permit your bathroom needs before demolition starts.

A bathroom is where California's water-conservation law shows up most directly. Civil Code Section 1101.4, added by SB 407 in 2009, says that for building alterations or improvements to a single-family home built on or before January 1, 1994, replacing noncompliant plumbing fixtures with water-conserving ones is a condition of final permit approval. Section 1101.3 defines what counts as noncompliant:

• A toilet that uses more than 1.6 gallons per flush.
• A showerhead with a flow capacity of more than 2.5 gallons per minute.
• An interior faucet that emits more than 2.2 gallons per minute.

Two other state codes apply as well. The 2025 Energy Code (Title 24, Part 6), in effect for permit applications from January 1, 2026, has residential lighting rules in Section 150.0(k): new installed lighting is to be high efficacy, and at least one installed luminaire in each bathroom is controlled by an occupancy or vacancy sensor that turns it off automatically. The 2025 California Electrical Code calls for ground-fault (GFCI) protection on bathroom receptacles, and bathroom receptacles are supplied by a 20-amp branch circuit.

An exhaust fan, a relocated shower valve or a new circuit can each bring their own permit and inspection. What applies to your bathroom is decided by the city at plan check and inspection, so confirm with the city.

HCD's summary of the 2025 CALGreen code (form HCD SHL 625) says bathroom exhaust fans are to be ENERGY STAR compliant and ducted to terminate outside the building. Unless the fan is part of a whole-house ventilation system, it is to have a humidity control that can be adjusted, manually or automatically, between a relative humidity of 50 percent or less and a maximum of 80 percent. For this rule, a bathroom is a room with a bathtub, a shower or a tub and shower combination.

By HCD's summary, CALGreen reaches new homes and alterations that increase a building's conditioned area, volume or size, so whether a fan replaced inside an existing bathroom has to meet the rule is a question for the plan checker. Lighting has a rule of its own here: the Energy Commission's 2025 compliance manual says lighting built into an exhaust fan is controlled independently from the fan.

Confirm with Building Safety what applies to your fan and lights before they are ordered.

Request the room's permit history first. Copies of past permits and plans can show whether an earlier remodel, a moved wall or newer wiring was permitted, which is easier to plan around before the tile comes off than after.

On a tub-to-shower conversion we check the drain location, the floor and the wall framing, then build the shower pan, waterproofing and tile. Ask Building Safety which inspections it wants before the walls are closed and tiled. The division posts a page titled Scheduled Inspections / Inspector Name and Contact Info.

If you want a curbless shower, a bench or grab bars, now or later, say so before demolition. The shower floor, the drain and the framing behind the tile are easier to plan while the walls are open.

• City of Costa Mesa: Building Division Permits and Plans Document Request (opens in a new tab)
• City of Costa Mesa: Scheduled Inspections / Inspector Name and Contact Info (opens in a new tab)

Which inspections a bathroom needs is the city's decision. Confirm with Building Safety before work starts.

If your home is in a homeowners association that requires approval for physical changes, Civil Code Section 4765 sets the ground rules for that review: the association's decision is to be in writing, and a disapproval has to explain why and describe how to ask for reconsideration. HOA approval and a city permit are separate. One does not replace the other.

A bathroom remodel is mostly inside, but an association may still set rules for work hours, parking and debris bins, and may want to see anything that changes outside, such as a new exhaust fan vent on an outside wall or a replaced bathroom window.