Can I build an ADU in Del Mar, California?
Yes. Del Mar allows one ADU plus one junior ADU on a single-family lot. You'll need a building permit and, in many cases, an administrative Coastal Development Permit, both approved by staff without a public hearing. A detached ADU can be up to 850 sq ft (1,000 sq ft with more than one bedroom) and 16 feet tall, with 4-foot side and rear setbacks.
| Number allowed (single-family lot) | 1 ADU + 1 junior ADU [1] |
| Max ADU size | 850 sq ft (1,000 sq ft if more than 1 bedroom) [2] |
| Guaranteed minimum size | 800 sq ft [3] |
| Attached ADU max size | 50% of the main home, or 800 sq ft if the home is under 1,600 sq ft [4] |
| Junior ADU max size | 500 sq ft, inside the house or attached garage [5] |
| Detached ADU height | 16 ft (18 ft near major transit) [6] |
| Side and rear setback (new ADU) | 4 feet [7] |
| Minimum rental term | More than 30 consecutive days [8] |
| Owner-occupancy (local text) | Owner must live on the property (since Jan 1, 2025) [9] |
| Approval | Building permit + administrative CDP, ministerial [10] |
What you can build
A lot with one house can have one ADU and one junior ADU (JrADU) [1]. The ADU can be a conversion inside the house or garage, an attached addition, a new or converted detached building, or an addition to an existing garage. If you build an attached ADU, no JrADU or second ADU is allowed. A JrADU must be inside the walls of the house, including an attached garage, and can be up to 500 sq ft [5]. Del Mar's code also bars a JrADU or second ADU when an ADU is converted inside the house. State law allows a converted ADU, a new detached ADU and a JrADU on the same single-family lot, so that limit may be overridden. Starting January 1, 2027, state law (AB 956) will also allow two new detached ADUs on a single-family lot.
Size, height and setbacks
- An ADU can be up to 850 sq ft, or 1,000 sq ft with more than one bedroom [2]. The city must accommodate at least an 800 sq ft ADU even if floor-area or lot-coverage limits would otherwise block it [3].
- An attached ADU is capped at 50% of the main home, or 800 sq ft if the home is under 1,600 sq ft [4].
- A detached ADU can be 16 ft tall, or 18 ft within a half mile of a major transit stop [6]. In the Bluff, Slope and Canyon Overlay Zone, the 14-ft overlay height applies.
- New ADU structures need 4-ft side and rear setbacks [7]. Conversions of existing structures can keep their current footprint.
Coastal limits
The whole city is in the Coastal Zone. ADUs aren't allowed on a beach, in a wetland or its buffer, within a coastal bluff setback, or in a designated highly scenic area [11]. Objective design standards also apply, such as no rooftop decks and earth-tone retaining walls.
Rental and occupancy
An ADU can be rented, but only for terms longer than 30 days, and can't be sold separately [8]. The city's standard plan notes require the owner to live on the property from January 1, 2025 [9]. State law (Gov. Code §66315) bars owner-occupancy requirements for ADUs, so that provision may be overridden. Requiring an owner to live on site is allowed only for a JrADU. ADUs also can't be used as short-term rentals in residential zones.
Parking
No parking is required within a half mile of a major transit stop. Outside the Coastal Commission appeals area, most ADUs need no parking. Shoreline and high-fire-risk lots and narrow streets may need one space.
Approval
You need a building permit and an administrative Coastal Development Permit, approved by staff with no public hearing [10]. Conversions of existing living space, and some attached ADUs, are exempt from the CDP. Before the building permit, you must record a deed restriction on sale, occupancy and rental.
See how Del Mar compares with 8+ other California towns on accessory dwelling units (adus) →
Next steps
- Check your zone and overlays (Coastal Bluff, Bluff/Slope/Canyon, Lagoon, Floodplain, CDP appeals area) with the Planning & Community Development Department.
- Prepare a dimensioned site plan, floor plan, sections and elevations, and show protected Torrey pine and Monterey cypress trees, following the city's ADU checklist.
- Apply for a building permit and an administrative Coastal Development Permit (unless your project is exempt); add a geotechnical report if you're in the Coastal Bluff Overlay Zone.
- Record the required deed restriction with the County Recorder and file it with the city before the building permit is issued.
Common questions
- Are ADUs allowed in Del Mar, California?
- Yes. Del Mar allows one ADU plus one junior ADU on a single-family lot. You'll need a building permit and, in many cases, an administrative Coastal Development Permit, both approved by staff without a public hearing.
- How big can an ADU be in Del Mar, California?
- A detached ADU can be up to 850 sq ft (1,000 sq ft with more than one bedroom) and 16 feet tall, with 4-foot side and rear setbacks.
- Do I have to live on the property to have an ADU in Del Mar, California?
- The local text says the owner must live on the property, since Jan 1, 2025.
- Can I rent my ADU in Del Mar, California?
- Only for more than 30 consecutive days, and short-term rentals are prohibited in an ADU in residential zones.
California's statewide ADU law
California's ADU law (Gov. Code §§66310–66342, recodified from §65852.2; latest amendments effective January 1, 2026) overrides conflicting city rules, including in charter cities. Cities must approve ADUs ministerially (no hearing) within 60 days of a complete application, or the permit is deemed approved.
What cities cannot require or do:
- Owner-occupancy for an ADU.
- A minimum lot size.
- Side or rear setbacks over 4 feet for a new ADU, or any setback for a converted existing structure.
- Size, lot coverage or floor-area rules that block an ADU of at least 800 sq ft. Size caps can't be under 850 sq ft (1,000 for 2+ bedrooms).
- Parking within half a mile walking distance of public transit, or replacement parking for a garage converted to an ADU.
- Impact fees on ADUs of 750 sq ft or less.
By right on a single-family lot: one converted ADU plus one junior ADU (JADU, up to 500 sq ft inside the house), plus one new detached ADU (up to 800 sq ft, 16 ft tall). Owner-occupancy may be required only for a JADU that shares a bathroom.
Short-term rentals: cities may bar ADU rentals under 30 days, and must for by-right ADUs, JADUs and SB 9 units.
Coming January 1, 2027: AB 956 raises the by-right count to two new detached ADUs per single-family lot.
SB 9 (§§65852.21, 66411.7) allows two homes on a single-family lot, or a split into two lots of at least 1,200 sq ft (with a 3-year owner-occupancy affidavit).
What the ordinance says
- Sec. 30.91.040(B), Municipal Code Chapter 30.91 - Accessory Dwelling Units, p. 1
A lot with an existing or proposed single dwelling unit is permitted to develop a maximum of one ADU (in compliance with Section 30.91.040) and a maximum of one JrADU (in compliance with Section 30.91.050) per lot.
- Sec. 30.91.040(G)(1), Municipal Code Chapter 30.91 - Accessory Dwelling Units, p. 1
The interior floor space within the surrounding exterior walls of the ADU (calculated from the inside face of wall studs) shall not exceed 850 square feet in size, or 1,000 square feet maximum if the ADU has more than one bedroom.
- Sec. 30.91.040(G), Municipal Code Chapter 30.91 - Accessory Dwelling Units, p. 1
In accordance with California Government Code Section 66321(b)(3), as amended, the City shall accommodate an ADU at least 800 square feet in size, which is also known as the "universal" ADU size provision.
- Sec. 30.91.040(G)(5), Municipal Code Chapter 30.91 - Accessory Dwelling Units, p. 1
The total floor area of an attached accessory dwelling unit shall not exceed 50 percent of the primary dwelling or 800 square feet if the primary dwelling is less than 1,600 square feet.
- Sec. 30.91.050(A), Municipal Code Chapter 30.91 - Accessory Dwelling Units, p. 1
A Junior Accessory Dwelling Unit (JrADU) is a small dwelling unit that is no more than 500 square feet in size and contained entirely within, and accessory to, an existing, or proposed, habitable primary Single Dwelling Unit pursuant to the regulations in Section 30.91.050 and California Government Code section 65852.22.
- Sec. 30.91.040(K)(1), Municipal Code Chapter 30.91 - Accessory Dwelling Units, p. 1
The maximum building height of a detached ADU shall not exceed 16 feet above grade.
- Sec. 30.91.040(N), Municipal Code Chapter 30.91 - Accessory Dwelling Units, p. 1
A side and rear setback of four (4) feet shall be required for a new ADU structure, except as follows:
- Sec. 30.91.040(F), Municipal Code Chapter 30.91 - Accessory Dwelling Units, p. 1
If rented, the term for rental of an ADU in a residential zone shall be for a term longer than 30 consecutive days per Government Code section 66315, as amended.
- Sec. 30.91.030(A)(1)(e)(ii), Municipal Code Chapter 30.91 - Accessory Dwelling Units, p. 1
Until December 31, 2024, the City will not require the property owner to occupy the primary unit or the ADU for newly created ADUs. Effective January 1, 2025, the property owner shall reside on the property in either the primary dwelling unit or in the ADU.
- Sec. 30.91.030(A), Municipal Code Chapter 30.91 - Accessory Dwelling Units, p. 1
All Accessory Dwelling Units and Junior Accessory Dwelling Units shall comply with applicable state and local building codes and shall require approval of a building permit and Administrative Coastal Development Permit as applicable in 30.91.030.E.
- Sec. 30.91.040(V), Municipal Code Chapter 30.91 - Accessory Dwelling Units, p. 1
ADUs shall not be located or approved where the ADU is located on: a beach, a wetland or its buffer, seaward of the mean high tideline, in an environmentally sensitive habitat area or its buffer, within a coastal bluff setback, or in an area designated as highly scenic area as determined by the City's certified Local Coastal Program.