ADUs on Del Mar duplex and multifamily lots
| Lot | Allowed (DMMC §30.91.060) |
|---|---|
| Two existing units (zone allows two) | Up to two ADUs: one per unit, inside the walls, attached at first story (16 ft), or detached (16 ft); not attached to each other; first story preferred |
| Three or more units | Convert shared non-living space (storage, boiler rooms, attics, basements, garages) up to 25% of units; not space controlled by one unit; can't remove required access or amenities |
| Detached on multifamily lots | Up to two, 16 ft, 4 ft side/rear, zone street setbacks, coastal setbacks; at least 800 sq ft accommodated unless coastal findings |
| JrADUs | Not allowed on multiple dwelling lots (except via the Incentive Program) |
State law (Gov. Code §66323) now allows up to eight detached ADUs on lots with existing multifamily dwellings. Del Mar's code lists two, harmonized with the Coastal Act. Ask Planning which applies to your lot.
Checklist
- Count existing legal units
- Identify shared non-living space
- Check coastal and view setbacks
- Consider the Incentive Program for bonus units
Converting shared space
On lots with three or more units, the space must not be inside, or solely controlled by, one unit. Typical candidates are common storage rooms, boiler rooms, attics, basements and garages. The conversion must meet building code for a dwelling and can't remove required access, open space or recreation amenities under existing permits.
Duplex design rules
Each duplex unit can have one ADU. First-story placement is expected; a second story is allowed only when there's not enough buildable area and it minimizes impacts. The maximum possible square footage goes on the first story.
Bonus units
The Incentive Program awards proportional bonus ADUs or JrADUs on lots with three or more units in the RM, R2 and commercial zones when owners deed-restrict low-income units, up to 15 per project and exempt from FAR and lot coverage. Properties with nonconforming density qualify if they have an on-site property manager.
Sources, checked Oct 14, 2026: Del Mar Municipal Code Chapter 30.91 (June 2025) · Gov. Code §66323.
Questions
How many ADUs can a Del Mar duplex have?
Up to two, one per unit, not attached to each other.