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

Campbell ADU permits — the key details

California Government Code Section 65852.2 is the legal bedrock: the state mandates that cities must allow at least one ADU per single-family residential lot, and cannot impose owner-occupancy requirements, cannot deny a qualifying ADU based on design review, and must process applications ministerially within 60 days. Campbell's Building Department must follow this statute. The city's local ordinance (adopted in 2020, updated in 2022) sets dimensional rules: detached ADUs must be setback 5 feet from side and rear property lines, cannot exceed 55% of the primary dwelling's floor area or 1,200 square feet (whichever is less), and must provide at least one off-street parking space on the property (though this is often waived in transit-accessible zones). For garage conversions or above-garage ADUs, Campbell follows IRC R310 (egress window requirements: minimum 5.7 square feet operable, sill height no more than 44 inches) and requires separate utility metering — you cannot share water, sewer, or electric panels with the primary residence. A detached ADU on a Campbell lot triggers a full building permit (Plan Check) with foundation design per IRC R401–R403 (frost depth is minimal on the coast but matters in the foothills — east of Hwy 17, assume 12–18 inches), framing, mechanical, electrical, and plumbing reviews. Junior ADUs (interior accessory units carved from the existing primary dwelling, sharing kitchen or bathroom with the main house) are permitted under AB 68 and typically have lower fees and faster turnaround because they don't require foundation or new utility runs.

Campbell's permit application process is now fully online via the city's permit portal. You must submit: (1) site plan showing lot lines, setbacks, parking, utilities, and primary dwelling; (2) floor plans and elevations (ADU and primary house); (3) electrical single-line diagram and panel schedule showing separate service or sub-meter; (4) plumbing riser diagram showing separate connection or compliance with code; (5) foundation plan if detached (geotechnical report not usually required unless site is in a landslide hazard zone or near a fault — Campbell's Building Department website specifies this). The city's plan-review staff has 30 days to either approve your application or issue an incomplete-application notice; if you cure defects within 30 days, the clock resets. Once approved, Plan Check is complete and inspections commence. The 60-day clock from AB 671 runs from submission through issuance of the permit, not to final sign-off. For a typical detached ADU with no complications, expect Plan Check in 3–5 weeks and inspections in 2–4 weeks (foundation, framing, rough electrical/plumbing, insulation, drywall, final). Total timeline: 6–10 weeks if you submit a complete application.

Parking is a common rejection point, but Campbell's rules are favorable: ADUs located within 0.5 miles of public transit (VTA bus routes that serve Campbell qualify) are exempt from parking requirements entirely. Off-transit ADUs must provide one space — this can be a driveway spot, a garage space, or a newly poured pad. Tandem parking (one car behind another in a driveway) is allowed. If your lot cannot physically fit one additional parking space without violating setbacks or encroaching on the street, you must request a parking waiver; Campbell's Building Department has discretion to grant waivers on small lots (under 5,000 sq ft) in the urban core. This is where the state law's override of local zoning becomes crucial: some cities used 'parking impossibility' as a disguised way to deny ADUs. Campbell, as of 2022, interprets this narrowly — you must genuinely prove you cannot meet the requirement, not that it is inconvenient.

Utility connections trip up many applicants. Campbell requires detached ADUs to have separate water meters and separate sewer connections (not sharing a branch line with the primary house). Separate electric service is required; if the lot's service entrance cannot accommodate a second 100-amp panel, you must install a sub-meter on the same service with a disconnecting means accessible from outside the ADU. If you plan to rent the ADU, this is non-negotiable — fire and insurance code treat separate utilities as essential. Gas can be shared (a single meter with dual regulators is acceptable), but water and sewer triggers inspections by Campbell's Public Utilities Division. The water meter inspection adds 5–10 days to timeline; the sewer inspection (camera work on the new lateral) can add 1–2 weeks. Plan accordingly. Electrical is usually approved in-house by the Building Department's electrical inspector.

Finally, understand that Campbell's Building Department issues the ADU permit, but the city's Planning Division may also flag land-use issues. If your lot is zoned for a specific use that the Planning Director interprets as incompatible with ADU rental (extremely rare in Campbell's current code), a Planning Director Certificate may be required before the Building permit issues. This is also rare because state law preempts most local land-use conflicts. However, Campbell has designated certain Wildland-Urban Interface (WUI) zones on the eastern and southern slopes where defensible-space requirements (100-foot radius fuel break around structures) apply to all new construction, including ADUs. If your lot is in a WUI zone, you will need a fire-defensible-space plan as part of your permit application; this typically adds 2–3 weeks to Plan Check but is not a denial trigger — just additional design work. Check the city's interactive zoning map before you design; it will show WUI overlays.

Three Campbell accessory dwelling unit (adu) scenarios

California state law preempts Campbell's local zoning for ADUs

This is the single most important fact for Campbell ADU applicants. AB 881 (2019) and AB 662 (2021) amended Government Code Section 65852.2 to strip cities of discretionary authority over ADUs. Campbell cannot impose owner-occupancy requirements, cannot deny a qualifying ADU on 'design compatibility' grounds, cannot set lot-size minimums stricter than state law (which allows ADUs on any single-family lot), and cannot require discretionary approval (use permits, variances, design review). When these laws passed, many Bay Area cities including some in Santa Clara County initially tried to maintain restrictive local rules. Campbell's Building Department and Planning Division eventually aligned (updated local ordinance in 2022) to comply. The result: your ADU application is ministerial, not discretionary. There is no public hearing, no neighbor notification requirement, no 'compatibility' scorecard. If you meet setbacks, parking, and utility requirements, the application is approved. This is radically different from typical commercial projects or conditional uses in Campbell, where a Planning Commission hearing is standard. The 60-day clock (AB 671) applies: from the moment you submit a complete application, the city has 60 days to either issue the permit or deny it (denial is rare if you meet the objective standards). If the city misses the deadline without justification, your application is deemed approved by operation of law.

One subtlety: Campbell's local ordinance sets objective standards (5-foot setbacks, 55% of primary dwelling size or 1,200 sq ft max, one parking space or waiver). These are enforceable and objective. But if an applicant's project does not fit the local standard — e.g., a 1,400 sq ft ADU on a small lot — the applicant can argue that the local standard conflicts with state law, which is silent on square footage and allows cities to set 'reasonable' limits. Campbell's 1,200 sq ft cap has been litigated in other California counties; some courts have held that it is reasonably related to protecting neighborhood character and is not preempted by state law. However, Campbell has also issued guidance (on its Building Department FAQ, though the URL changes) stating that the 1,200 sq ft limit applies only to detached ADUs, not to above-garage or conversion ADUs. If your project is close to the threshold, contact the Building Department's ADU coordinator (email via the permit portal) to confirm applicability before you design.

Practical upshot for a Campbell homeowner: do not assume your neighbor can block your ADU by objecting at a Planning meeting, because there is no Planning meeting for a ministerial ADU. Do assume the city will check setbacks, parking, and utilities meticulously — these are the objective gates. Do not expect delays due to design review or neighborhood opposition; delays are usually caused by incomplete plan submission or by utility infrastructure work (sewer main not in place, water pressure insufficient, etc.). And do plan for the 60-day clock plus inspections: even if your permit is issued on day 58, inspections can take 4–6 weeks, so total calendar time to occupancy is still 3–4 months.

Utility metering, fire-defensible-space overlays, and foothills-specific concerns in Campbell

Campbell straddles two terrain types: the flat Bay Area bottomland (west of Highway 17, near the Levi's Stadium area) and the foothills (east of Highway 17, toward Mount Hamilton). Each has distinct utilities and fire-risk profiles. Bottomland lots (Westmont, Rose Garden, Sunnyvale border) typically have older sewer and water infrastructure; the water main is adequate, sewer has capacity, and soils are bay mud (soft, low-bearing, frost depth negligible for foundation design). ADUs here encounter utility delays mainly if the water main requires replacement (old galvanized pipe, low pressure) or if the sewer lateral is blocked. Foothills lots (Hamilton Avenue corridor, Sycamore Drive area) have newer, oversized utilities, but soil is granitic and rocky — sewer trenching costs 2–3x more than bottomland, and geotechnical reports are often required if the lot is in a mapped landslide-hazard zone. The Campbell Building Department's website includes a fire-hazard overlay map; if your foothills lot falls in the WUI zone, you must submit a fire-defensible-space plan as part of your ADU permit. This plan is reviewed by the fire marshal and adds 2–3 weeks to Plan Check. Campbell Fire Department requires: all vegetation within 30 feet of the structure to be pruned to 10 feet above ground; all vegetation between 30 and 100 feet to be spaced at least one tree-diameter apart and pruned to 6–10 feet. This is not a denial reason — it is a design requirement. Many applicants hire a fire consultant (cost: $800–$2,000) to prepare this plan; some do it themselves with guidance from the city's fact sheet.

Utility metering for detached ADUs is non-negotiable in Campbell. The Building Department will not approve a permit without separate water and sewer metering shown on the plans. For electric, if the main panel has space, a sub-panel is preferred; if not, a sub-meter on the main service is acceptable. Gas can be shared (one meter with dual regulators). Water metering: you must include a new water meter pit (typically 18 x 24 inches concrete vault near the property line or at the street). The water meter itself is installed by Campbell Public Utilities Division during a post-framing inspection — you cannot turn on water to your ADU until the meter is in place and the connection is surveyed. Sewer: a new lateral (typically 4-inch PVC or cast iron) must be trenched from the ADU's stack to the public sewer main at the property line. If the main is deep (8–12 feet, common in foothills), costs escalate. A soils test pit (cost: $1,500–$3,000) may be required before design if the lot is in an expansive-soil or high-water-table area — Campbell can trigger this if there is any question about sewer gravity flow or if the main is more than 150 feet away. None of this bars your permit, but all of it must be shown on the plan and inspected. The public utilities inspection is often the longest-lead item; plan for 1–2 weeks after the sewer lateral is roughed in before Campbell Public Utilities will inspect the connection and allow you to proceed to final.

A third Campbell-specific concern is electrical service. Many older neighborhoods on the west side have 100-amp main service — barely adequate for a primary dwelling, let alone an ADU. If you want to build a detached ADU with electric sub-panel or sub-meter, you may need a main-service upgrade (100 to 200 amps). This requires an application to PG&E, a site survey, and often a service-line replacement (can cost $2,000–$5,000 if the existing line is buried and requires replacement). This work must be coordinated with your permit timeline. If you are planning to upgrade, tell the Building Department early in the pre-application phase; they may flag it during Plan Check so you can arrange it before inspections. Some applicants choose a smaller ADU (500–600 sq ft) powered by an 80-amp sub-panel to avoid the main upgrade cost. This is a legitimate design strategy and is explicitly allowed in Campbell's ADU ordinance.

Common questions