ADU rules in Burlingame

Detached ADUs are allowed with a ministerial Building Division permit on any lot with an existing or proposed single-unit or multi-unit dwelling: Table 25.10-1 lists ADUs as an accessory use (A) in R-1, R-2, R-3 and R-4, and § 25.48.030.D.3, which prevails over other zoning text under A.2, also reaches the mixed-use and Downtown Specific Plan districts whose use tables have no ADU row. A single-unit lot may take either one new attached or detached ADU built to the local standards in subsection F (up to 1,000 sq ft of interior livable space, 16 ft, 4 ft side and rear setbacks) plus a JADU, or the state-exempt set in E.10 (a conversion ADU, a JADU and one new detached ADU of up to 800 sq ft with 4 ft setbacks). Lots with an existing multi-unit building may add up to eight detached ADUs (never more than the number of existing units), and lots with a proposed one up to two. Detached units may rise to 18 ft within one-half mile of a major transit stop or high-quality transit corridor (plus 2 ft for a roof pitch matching the house) or beside a multistory multi-unit building, and no Hillside Area Construction Permit is needed (25.70.020.C.3).

Attached ADUs (additions to an existing or proposed home, including a new basement beneath it) and interior ADUs converted from the home's living area, basement or attached garage are allowed ministerially in the same districts. A new attached addition follows the local standards: up to 1,000 sq ft of interior livable space and the lower of 30 ft (25 ft in the Hillside Overlay) or the district height limit, never more than two stories. Conversions of existing or proposed space on the state-exempt path have no size cap (an accessory-structure conversion may grow 150 sq ft for ingress and egress) and may be paired with a JADU of up to 500 sq ft inside the single-unit home, attached garage included. On multi-unit lots, ADUs may also be carved out of non-livable space (storage rooms, attics, basements, garages) up to 25 percent of the existing units, at least one. Ord. 2035 (2024) abolished the separate Planning Division ADU Permit, so a building permit is the only approval.

Ord. 2046 restated the subsection F cap as '1,000 square feet of interior livable space' for attached and detached ADUs alike, above the 850/1,000 sq ft floors in Gov. Code 66321(b)(2) and with no percent-of-home limit. ADUs up to 800 sq ft are exempt from floor area ratio and lot coverage, but a larger unit counts in full and must fit the lot's FAR and coverage limits (F.2), so on an R-1 lot already near its FAR the practical cap is 800 sq ft; front setbacks may not block an 800 sq ft unit with 4 ft side and rear setbacks, while units over 800 sq ft must meet them. The state-exempt detached unit is capped at 800 sq ft 'in floor area' (E.10.b; the statute says livable space), conversions of existing or proposed space have no cap, and a JADU may not exceed 500 sq ft of interior livable space. The city's ADU Development Guide page adds 'Cannot be more than 50% of the existing dwelling unit square footage' for non-exempt units, a limit absent from § 25.48.030 (it mirrors Gov. Code 66314(d)(4), which covers attached units only and which 66315 frames as a maximum standard), while the city FAQ says an ADU 'can be up to 1,000 square feet of interior livable space'.

§ 25.48.030.E.3.c says 'ADUs are not subject to any owner-occupancy requirement,' matching Gov. Code 66315. Ord. 2046 narrowed the JADU rule to the state standard in 66333(b): an owner must live in the main home or the JADU only when the JADU shares sanitation facilities with the house, and never when the property is owned entirely by another governmental agency, land trust or housing organization. Every JADU still needs a deed restriction recorded before the building permit (no separate sale, size and attributes fixed), which the owner may have removed after installing separate sanitation or eliminating the JADU (E.7), as 66333(c) requires; the city FAQ's statement that the deed restriction applies only when a bathroom is shared understates the code.

Subsection H requires one off-street space per ADU, which may be tandem or in a setback, but waives it within one-half mile of public transit (defined as any bus stop, train station or other fixed-route, set-fare service), in an architecturally and historically significant historic district, for an ADU inside the existing or proposed home or an existing accessory structure, where on-street permits are required but not offered, within one block of a car-share stop, and for an ADU filed with a new home that meets one of those tests. State-exempt ADUs are outside subsection H altogether (E.10, amended at the 1-12-2026 Planning Commission hearing), JADUs need no parking, and garages, carports or spaces demolished or converted for an ADU need not be replaced. The flat one-space text also reaches studios, which on a plain reading exceeds Gov. Code 66314(d)(10)(A) (one space per unit or per bedroom, whichever is less), so state law controls there under A.2. The city FAQ names the Burlingame and Broadway Caltrain stations, Millbrae BART and El Camino Real as the city's major transit stops and high-quality transit corridor.

ADU and JADU applications are building permits 'considered by the Building Division ministerially and without discretionary review or public hearing' (C.1): a completeness determination within 15 business days, approval or denial within 60 days of a complete application, and deemed approval if the city misses the 60 days; Ord. 2046 added an appeal of an incompleteness determination or denial to the Planning Commission (C.5). ADUs are excluded from Major Design Review for new dwellings (25.68.020.C.1.a) and from Hillside Area Construction Permits (25.70.020.C.3), and Ord. 2035 ended the former Planning Division ADU Permit. One sequencing rule reaches past state law: an attached ADU or JADU filed together with an addition or new home that needs design review or another discretionary permit waits for that decision before its 60-day ministerial review (C.3), whereas Gov. Code 66317(a)(3) allows the delay only when the ADU is filed with a new dwelling.

ADUs 'may not be rented for fewer than 30 consecutive calendar days and may not be used as a short-term rental' (E.3.b), and JADUs may be rented 'no fewer than 30 consecutive calendar days' with the same short-term bar (E.4.a), both wording changes made by Ord. 2046. BMC 6.56.030 (Ord. 1989, 2020) separately says short-term rentals 'are not permitted in accessory dwelling units' while allowing registered short-term rentals (under 30 days) of a host's primary residence, un-hosted stays capped at 120 days a year. The local 30-day floor is lawful for ordinary ADUs under Gov. Code 66315, but ADUs approved on the state-exempt path and JADUs must be rented for terms longer than 30 days (66323(e), 66333(g)), so 31 days is the practical minimum for them. ADUs may be rented separately but not sold or conveyed apart from the main home, except as tenancy-in-common units developed by a qualified nonprofit under 66340 and 66341 (E.3.a); the city has not opted into 66342 ADU condominiums.