Bathroom Remodel Permit in Los Altos, CA (2026)

Research by DoINeedAPermit Research Team · Updated May 2026

The Short Answer

A full bathroom remodel in Los Altos requires a permit if you relocate any plumbing fixture, add electrical circuits, install a new exhaust fan, or modify any walls. Surface-only work — tile, vanity, or faucet replacement in-place — does not require a permit.

Los Altos Building Department uses an online permit portal and enforces strict waterproofing assembly specifications that differ from neighboring jurisdictions — specifically, you must detail your shower/tub membrane system (cement board + membrane, HardieBacker, or equivalent) on your plans before submittal, which catches many first-time applicants off guard. Unlike some Bay Area cities that allow verbal approvals for minor relocations, Los Altos requires a full plan set for any fixture movement or new exhaust ductwork. The city also has adopted the 2022 California Building Code with local amendments requiring AFCI (arc-fault circuit-interrupter) protection on all bathroom circuits — not just GFCI — which is stricter than the state minimum and requires coordination with your electrician before permitting. The city's review timeline typically runs 2–4 weeks for bathroom remodels because the planning counter staff cross-references plumbing trap-arm lengths, drain-slope calculations, and ventilation duct sizing against IRC tables; incomplete electrical plans (missing AFCI notation) are the single most common rejection reason. Owner-builders can file for plumbing and general work but must hire a licensed electrician for any new circuits or fixture roughing.

What happens if you skip the permit (and you needed one)

Stop-work orders and fines: Los Altos Building Department can issue a citation with fines starting at $500–$1,000 per day of unpermitted work, plus an order to halt all activity until corrections and retroactive permits are filed.
Double permit fees and reinspection costs: If you apply for a permit after work is already done, Los Altos charges the original permit fee plus an 'after-the-fact' surcharge (typically 100% of the original fee), putting your total at $400–$1,600 depending on project scope.
Title issues and resale disclosure: Unpermitted bathroom work must be disclosed on a Transfer Disclosure Statement (TDS) at sale; buyers often negotiate $10,000–$30,000 price reductions or demand the work be permitted and inspected before closing.
Insurance claim denial: If a pipe fails or electrical fire occurs in an unpermitted bathroom, your homeowner's insurance can deny the claim outright, leaving you liable for all repairs — a $5,000–$15,000 exposure in a full remodel.

Los Altos full bathroom remodels — the key details

The threshold rule is straightforward: if you move a toilet, sink, tub, or shower to a new location, or if you add a new circuit, exhaust fan, or drain line, you need a permit. Los Altos Building Department enforces this consistently across all neighborhoods — there is no 'minor alteration' exemption. The core trigger is fixture relocation because any new drain or water supply line triggers plumbing code review (trap-arm length, slope, venting). The second major trigger is electrical: a new exhaust fan circuit, a relocated vanity light, or GFCI/AFCI upgrades all require an electrical permit. A vanity swap in the exact same location with the same supply lines does not require a permit, nor does replacing a faucet aerator or tile without disturbing framing or plumbing. The distinction hinges on whether the existing infrastructure (pipes, wires, structure) stays intact. If you're uncertain, call the Los Altos Building Department permit counter — they will answer yes/no in 5 minutes.

Waterproofing specifications are where Los Altos gets strict and different from many coastal California cities. The 2022 CBC (which Los Altos has adopted) requires a continuous, impermeable moisture barrier behind all shower and tub walls per IRC R702.4.2. Los Altos' local practice requires you to SPECIFY on your building plans exactly what waterproofing system you will use — cement board plus liquid membrane, HardieBacker plus membrane, a prefab shower pan, or Schluter/similar proprietary system. Simply saying 'waterproofed per code' is not enough; the plan reviewer will reject your application and ask you to name the product. This is a common surprise because many contractors assume the inspector will verify waterproofing quality at rough inspection, but Los Altos wants it locked down on paper first. If your bathroom is on a concrete slab (common in older Los Altos homes), you must also show a moisture barrier under any tile floor, and the city's reviewers often flag slope and drainage details on slab-on-grade bathrooms. Have your tile designer or contractor provide waterproofing product specs before you file.

Electrical code in Los Altos bathrooms has become more stringent. The 2022 CBC now requires AFCI (arc-fault circuit-interrupter) protection on all bathroom outlets and lighting circuits, not just GFCI (ground-fault circuit-interrupter) on outlets — this is stricter than the previous edition and stricter than the national NEC minimum. Los Altos Building Department enforces this by requiring an electrical plan that explicitly notes AFCI breakers or AFCI outlets on every bathroom circuit. A common error is submitting an electrical plan that shows only GFCI outlets; the reviewer will reject it and tell you that AFCI is now required. If you're adding a bathroom exhaust fan, the new circuit must be AFCI-protected at the panel, and the duct must terminate outside the building with a damper (IRC M1505.2). The duct cannot terminate into an attic or soffit; Los Altos inspectors catch this frequently. If your bathroom has an existing exhaust fan you're reusing, you should confirm with your electrician that the circuit meets current AFCI requirements — if it doesn't, you'll need to upgrade it as part of your remodel permit.

Trap-arm length and drain slope are codified in IRC P2706 and are frequently flagged in Los Altos plan reviews. When you relocate a toilet, the new drain line's trap arm (the section of pipe from the toilet trap to the vent stack) cannot exceed 6 feet in length, and the slope must be 1/4 inch per foot toward the main stack. If your bathroom layout forces a longer trap arm, you need a separate vent line or a mechanical vent (like an AAV — air-admittance valve), which adds cost and complexity. Los Altos reviewers check these calculations on plans; an incomplete drainage diagram is a common rejection. Before you submit plans, have your plumber sketch the new drain routing and confirm trap-arm distances. If the distance exceeds 6 feet, coordinate with your plumber about a vent solution so your plans can show it upfront.

Timeline and fees in Los Altos run $200–$800 for a full bathroom remodel, depending on the valuation of materials and labor (typically 1.5–2% of project cost). Online filing through the Los Altos permit portal cuts down on back-and-forth; you can upload plans and receive comments within 1–2 weeks. Most bathroom remodels pass plan review in one or two rounds if the plumbing and electrical plans are complete. Inspection sequence is: rough plumbing, rough electrical, framing/drywall (if applicable), and final. If you're only remodeling a single bathroom and not touching framing, the framing inspection may be skipped. Plan on 2–4 weeks for plan review and 1–2 weeks to schedule inspections; total elapsed time is typically 4–6 weeks from permit issuance to final sign-off. Hiring a licensed plumber and electrician speeds approval because the city has confidence in their plan details; owner-builders filing their own plans often trigger longer review cycles due to incomplete calculations.

Three Los Altos bathroom remodel (full) scenarios

Scenario A

Cosmetic vanity, faucet, and tile swap — same plumbing location, Hillview Avenue home

You're replacing the vanity cabinet, faucet, and tile in a single-story Hillview Avenue bathroom. The existing supply and drain lines are not being touched; you're simply removing the old vanity and tile, then installing new ones in the same footprint with the same supply connection points. The sink remains at its current location. This work is exempt from permitting because no fixture is being relocated, no new electrical circuits are being added (the existing light and outlet stay in place), and no plumbing lines are being extended or rerouted. The single caveat: if the new vanity requires different supply-line positioning within the wall cavity, you may need to adjust existing copper or PEX lines, but as long as you're not trenching new runs or changing the vertical drop, Los Altos does not require a permit. You can proceed with the work and do not need to file with the city. The tile work itself — even if it extends beyond the tub surround — does not trigger a permit as long as no underlying structure or waterproofing is disturbed. Total cost: $3,000–$8,000 (vanity, faucet, tile labor), zero permit fees. Do alert your homeowner's insurance that work is underway so there's no coverage gap, and keep receipts for the tile waterproofing prep (if you use a membrane) in case questions arise at resale.

No permit required (cosmetic swap) | Same fixture location | Existing electrical/plumbing | Zero permit fees | $3,000–$8,000 estimated project cost

Scenario B

Toilet relocation and new vanity 3 feet over — Los Altos Hills mid-century ranch

You own a 1960s ranch in Los Altos Hills and want to shift the toilet and vanity 3 feet toward the opposite wall to open up floor space. This requires moving the drain line (toilet drain and sink drain) and the supply lines to new locations. Moving the toilet triggers a full plumbing permit because the new drain run must meet IRC P2706 trap-arm requirements: the section from the toilet trap to the main vent stack cannot exceed 6 feet, and the slope must be 1/4 inch per foot. Your plumber needs to calculate the new trap-arm length and confirm it meets code; if the run is short (under 4 feet), it will likely qualify. You also need to reroute the sink supply lines and possibly the sink drain. The city will require a plumbing plan showing the new drain and supply routing, with dimensions and trap-arm length labeled. If the vanity light is being relocated, you'll also need an electrical permit for the new circuit run. The shower/tub waterproofing does not change, so no special waterproofing plan is needed. Permit fee: $250–$500. Plan review: 2–3 weeks. Inspections: rough plumbing (city inspector checks trap-arm slope and new vent connections), then final plumbing. This scenario showcases Los Altos' requirement that trap-arm calculations be shown on plans upfront — many DIYers assume they can 'figure it out on the fly,' but the city needs it documented before approval.

Permit required (fixture relocation) | Plumbing plan with trap-arm dimensions | $250–$500 permit fee | 2–3 week plan review | Rough + final plumbing inspections

Scenario C

Full shower-tub conversion with new exhaust fan and AFCI circuits — downtown Los Altos Victorian

You're gutting a 1920s downtown Los Altos Victorian bathroom: converting an old corner bathtub to a large walk-in shower, installing a new exhaust fan with ductwork to the roof, and upgrading electrical with new GFCI/AFCI outlets and vanity lighting on a dedicated 20-amp circuit. This is a high-complexity permit scenario that triggers multiple code sections. First, the tub-to-shower conversion requires a detailed waterproofing plan per IRC R702.4.2 because you're changing the water exposure footprint and likely building new walls. Los Altos requires you to specify your waterproofing system on plans — e.g., 'Schluter Systems shower kit with prefab pan' or 'cement board + Redgard membrane + tile' — before submittal. Second, the new exhaust fan duct must be sized per IRC M1505 (typically 4-inch diameter), routed to the outside roof with a damper, and shown on mechanical plans with exit termination detail. Third, all bathroom circuits must be AFCI-protected per 2022 CBC; your electrical plan must call out AFCI breakers at the panel or AFCI receptacles. The new 20-amp lighting/outlet circuit must be AFCI and cannot share a breaker with other bathrooms. You'll need a general permit (framing/drywall), plumbing permit (new drain, vent, supply), and electrical permit. Total permit fees: $500–$800. Plan review will take 3–4 weeks because the reviewer must cross-check waterproofing specs, trap-arm length, duct sizing, and AFCI notation. Inspections: rough framing, rough plumbing (drain/vent slope), rough electrical (AFCI breaker/outlet verification), drywall (moisture barrier check), and final. This scenario showcases Los Altos' strictness on waterproofing specs upfront and AFCI electrical requirements — common rejections occur when plans lack product names or AFCI notation.

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Waterproofing specifications: Why Los Altos catches what other cities miss

Los Altos' coastal-adjacent climate (3B-3C zone) experiences humidity, occasional heavy rain, and morning fog — conditions that make waterproofing failures visible to homeowners within months, not years. The city has responded by tightening waterproofing plan requirements: you cannot submit vague language like 'waterproofed per code' or 'tile installed per ANSI standards.' The plan must name a specific product or assembly. This is a departure from many neighboring cities (e.g., Palo Alto, Mountain View) where inspectors verify waterproofing quality at rough inspection without requiring upfront product specification. Los Altos Building Department enforces this because they've seen too many disputes arise when homeowners assumed a contractor's choice of membrane would be approved but the inspector rejected it at rough stage, forcing rework and cost overruns.

For tub/shower surrounds, Los Altos accepts three main waterproofing approaches: (1) traditional cement board (1/2-inch minimum) plus liquid membrane (Redgard, Aqua Defense, or equivalent); (2) HardieBacker or similar reinforced board plus membrane; (3) prefabricated shower pan systems (Schluter, Wedi, DuRock) that integrate waterproofing with substrate. Each requires different notation on plans. If you choose cement board, your plans should state 'Cement board, 1/2 inch minimum, fastened per manufacturer, with liquid waterproofing membrane applied to all surfaces.' If you choose a prefab system, your plans should reference the product name and size. The reason Los Altos insists on this upfront is that cement board + membrane is labor-intensive and easily botched; by locking down the product choice before work begins, the city avoids disputes about whether 'proper' waterproofing was actually installed.

Slab-on-grade bathrooms in Los Altos Hills and downtown areas require additional moisture planning. If your bathroom is on a concrete slab, you must show a moisture barrier (vapor retarder) under any tile floor, sloped toward a drain or perimeter, per IRC R702.4. Los Altos reviewers flag missing moisture barriers on slab bathrooms because capillary action can wick water up through the concrete, causing tile to pop and mold to grow underneath. If your slab lacks a moisture barrier, your plans should show either a liquid-applied barrier or a sheet barrier (6-mil polyethylene minimum) installed before flooring, with a coved edge at walls. This detail is often omitted because many contractors assume 'it's just a bathroom on concrete, no big deal,' but Los Altos makes you document it. If you're unsure whether your slab has an existing vapor barrier, discuss it with your plumber or general contractor before submitting plans.

AFCI and exhaust-fan ductwork: Los Altos' strict interpretation and common rejections

Los Altos adopted the 2022 California Building Code in 2023, which expanded AFCI (arc-fault circuit-interrupter) requirements to all bathroom lighting and outlet circuits, not just GFCI on outlets. Many contractors and homeowners submitted plans under the older 2019 code and assumed GFCI outlets were sufficient; Los Altos' reviewers now reject those plans outright and require AFCI protection at the breaker or outlet. The code change exists because AFCI detects subtle electrical arcing that precedes fires — a toilet cord rubbing on copper pipe, for example, or a wire nick inside the wall cavity — that GFCI (which only detects ground faults) would miss. Los Altos enforces this aggressively because electrical fires in bathrooms are a recognized hazard, and the city's liability exposure is high in older homes with aging wiring.

When you submit an electrical plan, you must specify: 'All bathroom circuits protected by AFCI breakers at the main panel' or 'AFCI receptacles installed at all outlets.' If you have multiple bathroom circuits, each must be AFCI-protected on its own breaker; you cannot run a bathroom circuit in series with a bedroom circuit and protect only one. The common mistake is assuming that a single AFCI outlet 'downstream' will protect all outlets on that circuit — it won't, because AFCI breakers (at the panel) offer broader protection than AFCI receptacles (at individual outlets). Los Altos plan reviewers flag this, and your electrician may need to revise the panel schedule. Cost impact is modest: AFCI breakers run $50–$80 each, versus $15–$30 for standard breakers.

Exhaust-fan ductwork rejections in Los Altos stem from two errors: (1) the duct terminating into an attic or soffit instead of the roof exterior, and (2) missing damper specifications. IRC M1505.2 requires exhaust ductwork to terminate on the roof, wall, or soffit exterior, with a back-draft damper to prevent cold air from flowing back into the bathroom when the fan is off. Los Altos reviewers check both details on mechanical plans. If your plans show a duct running into an attic, the reviewer will reject it. If you claim a damper will be installed 'per code' without naming a product or size, the reviewer will ask for specifics. Your plans should state: 'Exhaust fan ductwork, 4-inch diameter, smooth-walled rigid aluminum or approved flexible, routed to roof penetration, terminated with roof flashing and back-draft damper rated for 4-inch duct.' If your existing attic has insufficient ventilation (a common issue in older Los Altos homes), routing a new bathroom exhaust fan duct to the roof may trigger a request for attic ventilation calculations, adding cost and timeline. Coordinate with your HVAC contractor before submitting plans.

City of Los Altos Building Department
Los Altos City Hall, One North Santa Cruz Avenue, Los Altos, CA 94022
Phone: (650) 947-2600 (main line; transfer to Building Department) | https://www.losaltos.gov (search 'Building Permits' for online portal or permit application forms)
Monday–Friday, 8:00 AM–5:00 PM (closed holidays; confirm online before visiting)

Common questions

Can I do a full bathroom remodel as an owner-builder in Los Altos?

Yes, but with restrictions. California Business and Professions Code § 7044 allows owner-builders on residential property they own, but you must hire a licensed plumber for any plumbing work (drain, supply lines, fixture connections) and a licensed electrician for any electrical work (new circuits, rough-in, AFCI installation). You can do framing, drywall, tile, and finish work yourself. Los Altos Building Department requires licensed contractors for plumbing and electrical plan sign-offs; they will not issue a permit based on an owner-builder electrical or plumbing plan. File the general remodel permit in your name, but hire licensed subs for trade-specific rough inspections.

Do I need a permit if I'm only replacing a toilet or faucet in place?

No. Replacing a toilet, faucet, or fixture in the same location with the same supply and drain connections does not require a permit in Los Altos. If you're swapping the toilet to a new model, removing the old one, and installing the new one with the same closet flange and fill valve, you don't need to file. The exception: if the new fixture requires different water-supply sizing or a different trap configuration, and you're relocating supply or drain lines, then you need a permit.

What happens if I install a new exhaust fan but don't route the duct to the roof?

Los Altos Building Department will not approve it. Ductwork must terminate outside the building per IRC M1505.2 — not into the attic, soffit, or crawl space. If your duct terminates indoors, the inspector will fail the final inspection and order the duct rerouted to the roof. This is a common issue in older bathrooms where previous owners ran exhaust ducts into the attic to 'save money,' but the city no longer permits it. Plan and budget for roof penetration and flashing from the start.

What's the difference between GFCI and AFCI, and why does Los Altos require both in bathrooms?

GFCI (ground-fault circuit-interrupter) protects against shock by monitoring current leakage between the hot and neutral wires — if water conducts electricity to ground, GFCI shuts off power. AFCI (arc-fault circuit-interrupter) detects unintended electrical arcing (sparking) that can precede fires, caused by damaged insulation or worn wire. Los Altos now requires AFCI on all bathroom circuits per the 2022 CBC because bathroom environments (moisture, steam, wire movement) create conditions where AFCI prevents fires that GFCI cannot. AFCI is installed as a breaker at the main panel or as a special outlet. Your bathroom needs both: AFCI breakers for branch circuits (per code), and GFCI outlets at the sink per NEC 210.8. Many contractors conflate them; clarify with your electrician that AFCI is the new requirement, separate from GFCI.

How long does plan review take for a full bathroom remodel in Los Altos?

Typical plan review takes 2–4 weeks if your plans are complete (plumbing trap-arm calculations, waterproofing product specs, electrical AFCI notation, duct termination detail). Incomplete plans are returned for revision, adding 1–2 weeks per round-trip. Once approved, scheduling inspections typically takes 1–2 weeks. Total elapsed time from permit application to final approval is 4–6 weeks in a normal year; add time if the project includes structural framing or if the plumbing layout is complex (e.g., relocating vent stacks).

What permit fees should I expect for a full bathroom remodel in Los Altos?

Permit fees in Los Altos are typically 1.5–2% of the project valuation (materials plus labor). A full bathroom remodel (fixture relocation, new exhaust fan, electrical circuits) usually costs $15,000–$40,000, resulting in permit fees of $225–$800. Ask the permit counter for an estimate based on your scope; they use a valuation table. If you're not sure of the total cost, estimate conservatively and ask for a refund if your project comes in lower. Separate plumbing and electrical permits may be charged separately (e.g., $150 plumbing + $150 electrical + $150 general = $450 total).

I'm in a historic district in downtown Los Altos. Does that affect bathroom remodel permits?

Yes. If your home is in the Los Altos Historic District, additional design review may be required for exterior changes (e.g., new roof duct termination visible from the street). Interior bathroom remodels are generally not subject to historic design review unless the work is visible externally or involves removing original tile/finishes that are listed as character-defining. Check with Los Altos Planning Department before submitting your permit to clarify whether your scope triggers historic review; if it does, add 1–2 weeks to your timeline.

Can I use a wet vent for the toilet drain in my relocated bathroom?

Not in Los Altos under the 2022 CBC. California amended the IRC to prohibit wet vents for toilets; the toilet drain must have its own dedicated vent to the roof or an air-admittance valve (AAV / mechanical vent) in approved locations. This is a common source of confusion because older code allowed wet vents. If your plumber mentions using a wet vent to save cost or space, clarify that Los Altos requires either a dedicated vent or an AAV per current code. AAV systems cost $100–$200 and can be installed in a wall cavity (not visible); they're a practical solution for tight layouts.

What if my pre-1978 home has lead paint in the bathroom? Do I need a permit for that?

If your home was built before 1978, the bathroom likely has lead-based paint. California (and Los Altos) require lead-safe work practices per EPA RRP (Renovation, Repair, and Painting) rules. If your remodel involves disturbing painted surfaces (drywall, trim, tile backing board), you must hire an EPA-certified lead-safe contractor or follow lead-safe practices yourself (encapsulation, HEPA vacuuming, containment). This is a federal requirement, not strictly Los Altos' enforcement, but the city may ask about lead practices at permit application. Budget $500–$1,500 for lead-safe precautions; it's mandatory, not optional, for pre-1978 homes.

Do I need separate permits for general, plumbing, and electrical, or one combined permit?

Los Altos allows one combined remodel permit that covers general, plumbing, and electrical work. At the counter, you file one application and one set of plans. The permit fee is calculated on total project valuation, not split by trade. However, each trade (plumbing, electrical) must have a licensed contractor sign the plan; you cannot file an electrical plan without a licensed electrician's seal. Simplest approach: hire a general contractor who pulls the permit and coordinates subs, or file the permit yourself and have your plumber and electrician sign the relevant plan pages.

Disclaimer: This guide is based on research conducted in May 2026 using publicly available sources. Always verify current bathroom remodel (full) permit requirements with the City of Los Altos Building Department before starting your project.

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