Detached ADUs in Del Mar
A detached cottage is the one ADU type in Del Mar that can sit alongside a junior ADU in the house. It's also the type most shaped by Del Mar's coastal rules: protected trees, bluffs, slopes and public views. This guide follows Del Mar Municipal Code Chapter 30.91 (June 2025), the city's ADU chapter as certified by the Coastal Commission and effective June 12, 2025.
Your options on a single dwelling lot
| Path | What you can build | JrADU too? |
|---|---|---|
| ADU within the house or a garage (attached or detached) | One ADU inside existing walls; up to 150 sq ft added only for ingress or egress | No |
| Attached ADU (addition sharing a common wall) | One ADU added to the house | No |
| ADU attached to an existing garage | One ADU joined to the garage (no other accessory structure) | No |
| Detached ADU (new or converted accessory structure) | One detached ADU | Yes, one JrADU inside the house or attached garage |
Source: DMMC §30.91.040(B).
Detached ADU standards
| Standard | Del Mar rule |
|---|---|
| Number | One detached ADU per lot |
| Size | 850 sq ft, or 1,000 sq ft with more than one bedroom, measured from the inside face of wall studs |
| Universal size | The city must accommodate at least 800 sq ft; area over 800 counts against FAR and lot coverage |
| Height | 16 ft above grade; 18 ft within half a mile walking distance of a major transit stop or high-quality transit corridor; 14 ft in the Bluff, Slope and Canyon Overlay Zone |
| Side and rear setbacks | 4 ft; eaves and overhangs may not encroach |
| Street setbacks | Zone street-fronting setbacks, unless needed to fit an 800 sq ft ADU |
| Building separation | 6 ft minimum between buildings |
| Converted structure | May add up to 150 sq ft for ingress and egress |
| Solar | Required for new, non-manufactured detached ADUs (on the ADU or house) |
| Sprinklers | Not required if the house has none |
Source: DMMC §30.91.040.
Coastal resource setbacks
Even a converted structure keeping a nonconforming setback must meet coastal setbacks: the coastal bluff setback, the Beach Preservation Initiative setback in the Beach Overlay Zone, the Bluff, Slope and Canyon Overlay setback, wetland and habitat buffers, and zone setbacks where needed to protect public ocean views. ADUs aren't allowed on a beach, in a wetland or its buffer, in a coastal bluff setback, or in a designated highly scenic area.
Step by step
- Map the lot: protected Monterey Cypress and Torrey Pines with dripline zones, slopes, bluff edge, flood zone, overlays.
- Pick the path: detached ADU, with or without a JrADU in the house.
- Design to the objective standards (see ADU design).
- Prepare the submittal: site plan with all square footages, two-direction sections, elevations, floor plan, utility and sprinkler information, construction parking and storage plan, FEMA elevation certificate if applicable.
- Submit the ADU Application Packet, fees and plans.
- Record the deed restriction before the building permit.
- Certify height, setbacks and square footage before framing inspection.
- Build with verified, licensed contractors; the permit expires two years after issuance without a certificate of occupancy.
Grading and slopes
A new ADU pad must sit on a slope no steeper than 4 to 1, stay out of substantially steep slopes (25% and 20 ft of relief), keep 20 ft from the top and 10 ft from the bottom of such a slope, and limit grading to 200 cubic yards of cut and fill combined. ADUs can't sit at a crest or ridgeline.
Questions homeowners ask
- Is an ADU always detached? No. In Del Mar you can build inside the house, attach an addition, attach to an existing garage, or build detached. Only the detached path also allows a JrADU.
- How close to the property line can a detached ADU be? 4 ft from side and rear lines, with no eaves in that 4 ft. Alley lots may count half the alley width.
- Does a detached ADU need parking? Usually not, but Del Mar requires one space in some shoreline and high fire risk areas and on streets 20 ft wide or less. See parking.
How Del Mar's detached ADU rules compare with state law
Del Mar's chapter starts from state ADU law and then layers on the protections in its certified Local Coastal Program. Most numbers match the state floor; the differences are coastal.
| Topic | State baseline | Del Mar addition |
|---|---|---|
| Height | 16 ft; 18 ft near major transit | 14 ft in the Bluff, Slope and Canyon Overlay Zone |
| Setbacks | 4 ft side and rear | Coastal bluff, Beach Preservation Initiative, slope, habitat and view setbacks still apply |
| Size | 850 / 1,000 sq ft; 800 sq ft universal | Coastal findings can reduce size where resources or access are affected, down to 150 sq ft |
| Grading | Not addressed | 200 CY cut and fill cap; 4:1 pad; no ridgelines |
| Trees | Not addressed | No ADU in a protected tree dripline unless needed for 800 sq ft |
Where detached ADUs work well in Del Mar
The code favors a flatter rear yard with room for 6 ft of building separation, no protected Torrey Pines or Monterey Cypress driplines, and no steep slope within 20 ft of the top edge. Lots in the Floodplain Overlay Zone can work too, with the lowest floor at base flood elevation plus one foot and flood-resistant construction, which also exempts the ADU from a Floodplain Development Permit.
Where they're hard
Lots on a coastal bluff, in a highly scenic area, or on a ridgeline. ADUs can't be placed in a coastal bluff setback, on a beach, in a wetland or its buffer, or in a highly scenic area designated by the LCP. Very High Fire Hazard Severity Zone lots need two evacuation routes and a parcel evacuation map, or an equivalent safety showing.
Decision checklist
- You want the JrADU option as well
- There's a buildable pad at 4:1 slope or flatter
- The footprint avoids protected tree driplines
- Grading stays under 200 CY
- You're comfortable with 16 ft (one story)
Sources, checked Oct 14, 2026: Del Mar Municipal Code Chapter 30.91 (June 2025) · City of Del Mar ADU page.
Questions
How big can a detached ADU be in Del Mar?
850 sq ft, or 1,000 sq ft with more than one bedroom, measured from the inside face of wall studs. The city must accommodate at least 800 sq ft unless coastal impacts require findings.
How tall can a detached ADU be in Del Mar?
16 ft above grade, 18 ft near major transit, and 14 ft in the Bluff, Slope and Canyon Overlay Zone.
Can I have a detached ADU and a JrADU?
Yes. A lot with a single dwelling can have one detached ADU plus one JrADU inside the house or attached garage.