Do I need a permit for an ADU in
Lomita, California?

Lomita ADU permits — the key details

California state law (Government Code 65852.22, 65852.32, and AB 881 effective 2022) sets the floor for what Lomita MUST allow. Detached ADUs of up to 800 square feet, with owner-occupancy of the main house, are now entitled to local approval if they meet setback, design, and utility standards. Junior ADUs (attached, non-owner-occupied optional under AB 881, limited to 500 sq ft and max 25% of main-house floor area) are also by-right. Importantly, state law preempts local zoning restrictions on ADU "use" — meaning Lomita cannot ban ADUs on the grounds of "residential character" or "density" anymore. However, Lomita still enforces design review (roofline, materials, massing), setback rules (typically 5 feet side, 20 feet rear for detached ADUs), and parking placement (which may be waived under state law if transit-adjacent). The key win for owners: parking is no longer required for ADUs in certain jurisdictions and income levels under AB 68/881; Lomita's current practice is to waive off-site parking if the property is within 1/4 mile of public transit (Caltrain, bus), but that varies. Always confirm the city's current ADU waiver list before design.

The Lomita Building Department applies a 60-day shot clock to ADU permits (AB 671 mandates this statewide). That clock starts when you submit a complete application (plan set, site plan, utility plan, narrative, proof of main-house occupancy or title). If the city issues a deficiency notice, the clock pauses; once you cure it, the clock resumes. Most straightforward detached ADUs (under 500 sq ft, standard setbacks, no grading or utility extensions) move through plan review in 45–60 days. Larger units, or those requiring design variance, site-plan review, or utility work on city property, may consume the full 60 days or trigger a Conditional Use Permit hearing (which extends timeline to 90–120 days and adds $2,000–$4,000 in application fees). Lomita's Building Department does NOT currently offer a pre-approved ADU plan list (unlike some Bay Area cities); you must submit custom plans, which means hiring an architect or designer (typically $2,000–$5,000) or using a state-approved plan service (SB 9 plans, now available from third-party vendors, cost $500–$1,500 and may require light customization).

Permitting fees in Lomita for ADU projects break down roughly as: base building permit (1.5–2.5% of construction cost, e.g., $2,500–$5,000 on a $200K build); plan review (flat $1,500–$2,500 or percentage-based); electrical permit ($500–$800); plumbing permit ($500–$800); mechanical permit ($300–$500 if applicable); and impact fees (schools, parks, traffic, ranging from $2,000–$5,000 for an ADU). Total permit + fees: $5,000–$15,000. Some cities offer ADU fee waivers for affordable-income projects; Lomita does not currently waive fees but may allow deferral if owner-occupant income qualifies. Bring proof of contract with licensed general contractor or owner-builder affidavit (CA Contractors State License Board Form RB-1) when you file. If you hire a GC, they pull the permit; if you are the owner-builder, you can pull it yourself (but must show trade licenses for electrical/plumbing subs). Lomita requires applicant name, property address, project description, and a valid California driver's license or ID.

Utility connections are often the surprise bottleneck in Lomita ADU projects. If your ADU shares the main house's water meter and electrical panel, you can use sub-metering or a main-panel breaker tap, which is fast and low-cost ($1,500–$3,000 total). But if separate utility connections are required (e.g., on a lot where the ADU is far from the main house, or on a peninsula lot with limited utility access), you'll need to show approval from Lomita Municipal Utilities (or the relevant provider — many Peninsula properties tap Santa Cruz or Coastside County Water District). Utility connection fees run $5,000–$15,000 per line (water + sewer + gas + electric) depending on distance and whether the meter is new or an existing auxiliary panel. On lots near Lomita's steep hillside terrain (common in the southern neighborhoods), utility trenching and grading can add $10,000–$30,000 if the site is rocky or requires retaining walls. Always pull utility-availability records from the city's GIS portal before design; the Building Department will flag utility constraints in their 60-day review.

Inspections for Lomita ADU projects follow the standard California building-code sequence: foundation (post-holes, footing depth, reinforcement for detached units); framing (structural, roof, egress windows per IRC R310); rough electrical, plumbing, and mechanical (all to code); insulation and drywall; final building inspection; and utility on-call from water and gas. If the ADU requires grading or site work, a grading and drainage inspection is mandatory. Owner-builders can attend inspections but must have licensed contractors (electrician, plumber) sign off on their respective trades before final. Timeline from permit issuance to final sign-off: typically 12–16 weeks for detached ADUs (4–6 weeks framing, 2–4 weeks rough trades, 4–6 weeks finish), longer if utility extensions are involved. Occupancy permit (CO) is issued only after all inspections pass and fees are paid; you cannot legally occupy the ADU until the CO is in hand.

Three Lomita accessory dwelling unit (adu) scenarios

Lomita's unique position on the Peninsula: state law preemption and local design friction

Lomita is a 2.5-square-mile incorporated town in unincorporated San Mateo County, wedged between Highway 1 and the coastal ridge. Historically, like many Peninsula towns, it restricted ADUs via zoning (single-family-only zones, no accessory-use permits). California's ADU laws (starting with SB 413 in 2015, then AB 68 in 2019, AB 881 in 2021, and AB 671 in 2022) have progressively overridden local restrictions. By 2023, Lomita had no legal grounds to refuse a compliant detached or junior ADU. What makes Lomita unique relative to neighbors like Portola Valley or Woodside is that it has NOT adopted a blanket ADU approval ordinance with pre-approved plans. Instead, the Lomita Planning Department still treats each ADU as a design-review project, requiring site plan, architectural elevation, roof-pitch alignment with neighbors, and color/material compatibility. This adds 15–25 days to the review cycle compared to towns like Half Moon Bay, which auto-approve ADUs under 600 sq ft if they meet setbacks.

The city's design expectations matter. Lomita wants ADUs to 'fit' the neighborhood character — pitched roofs (not flat), wood or stucco siding (not corrugated metal), and massing that defers to existing homes. On smaller hillside lots, where ADUs are often tucked into rear yards, the city may request deck privacy screening, retaining wall design, and grading plans. This adds $1,000–$3,000 to the plan-set cost. An SB 9 pre-approved plan (basic templates available from third-party vendors for $500–$1,000) must be customized to Lomita's massing and color expectations; a blank SB 9 plan will hit deficiency notice on first review. The upshot: Lomita is permissive under state law but still 'design-heavy' compared to faster-moving neighbors. Budget time and design dollars accordingly.

Lot size and parking are secondary but real frictions. Lomita's minimum lot size for a primary residence is 7,500 sq ft (Peninsula fire safety zone, common in hilly areas). For an ADU, state law requires only that it 'fit' the lot and meet setbacks; Lomita interprets this as needing at least one parking space on the property (unless transit-adjacent waiver is granted). On small urban Lomita lots (e.g., 5,000 sq ft, common in the town center), a detached ADU plus parking can be geometrically tight. The city may request a variance or conditional use permit if parking is missing, adding 4–8 weeks to the timeline. Always pull the lot survey and check parking/setback availability before design.

Utility and infrastructure constraints on the Peninsula: water, sewer, and grading complexity

The San Mateo County Peninsula is notoriously fragmented on water and sewer service. Lomita's western neighborhoods tap the Coastside County Water District (CCWD); eastern portions tap the San Francisco Public Utilities Commission (SFPUC) or local well systems (if unincorporated). South of Lomita, some properties rely on private or shared wells and septic tanks (common in rural Santa Cruz County). The Building Department's utility pre-check (required before you file) will reveal your water/sewer provider and any service-connection constraints. If CCWD or SFPUC, a new water meter is routine ($3,000–$5,000, 6–8 week wait). If you're on a private well or septic, ADU approval may trigger a San Mateo County Environmental Health review; septic systems have strict lot-size and setback requirements (e.g., 100 feet from wells, 50 feet from property lines), which can kill ADU viability on small lots. Sewer connections in hillside Lomita are also challenging: many older homes use long gravity laterals to distant mains, or pump stations on shared property. ADU sewer tie-ins can require easement negotiation, pump-station upgrades, or new laterals at $8,000–$15,000. Always budget for a pre-design utility report ($800–$1,500) to confirm feasibility before committing to an architect.

Grading and drainage are Lomita-specific pain points due to topography. The town rises steeply from Highway 1 (sea level) to peaks over 1,000 feet within 2 miles. Lot slopes of 15–30% are normal. If your ADU requires a new foundation pad, retaining wall, driveway, or utility trench on a slope, the city requires a geotechnical report (cost $2,000–$4,000) and a grading/drainage plan stamped by a civil engineer. These add 2–4 weeks to the design phase and $1,500–$3,000 to the plan-set cost. Soil types vary: coastal clay (east of Highway 1, expansive, slower drainage) and sandy loam (west toward the ocean). Clay soils require deeper, wider footings and may trigger grading review. Coastal sand is faster-draining but less stable; the city may require geotech input for design. Budget 14–18 weeks for hillside ADU construction due to site work; flat-lot projects move in 10–14 weeks.

One often-missed detail: Lomita's Coastal Zone. The western portions of town (roughly west of Highway 1) fall under California Coastal Commission jurisdiction. Even though Lomita is a local authority, any ADU within the coastal zone requires Coastal Commission consistency review; this is NOT a separate permit but adds 10–15 days of state-level plan review and may impose design conditions (setbacks from bluff edges, native landscaping, no net loss of agriculture, etc.). The Building Department will flag this at intake; if your lot is in the coastal zone, your architect must note it on the cover sheet and build in the extra timeline. East of Highway 1, Coastal Commission review is waived.

Common questions