Carlsbad ADU Regulations & Zoning

Carlsbad allows at least 2 detached ADUs for multifamily lots with an existing multi-family building. (Meaning: In order to build 2 ADUs, the property must already have at least a duplex on it, not just a single family dwelling)

Multifamily property owners are permitted to build as many ADUs as there are existing units, with a maximum of eight detached ADUs.

Additionally, a minimum of one accessory dwelling unit, or up to 25 percent of the existing multifamily units, is permitted within an existing multifamily dwelling, as a result of the conversion of non-habitable space including, but not limited to, storage rooms, boiler rooms, passageways, attics, basements, or garages.

Read more about the rules around how many ADUs you can build on a multifamily lot.

Yes. In Carlsbad “Guest house” or “accessory living quarters” mean  living quarters within an accessory building for the sole use of persons employed on the premises, or for temporary use by guests of the occupants of the premises. Such quarters shall have no kitchen facilities and shall not be rented or otherwise used as a separate dwelling unit.

Read more about guest quarters.

The height limit for ADUs in Carlsbad is typically 16′, but you may build a two story ADU in Carlsbad:

• Above a garage (must conform with the applicable height limit of the zone, but not to exceed one-story above a one-story garage). Read more about building an ADU above a garage.
• On on residential lots within one‐half mile walking distance of a major transit stop (up to 20′ in height, including up to two feet allowed to accommodate the ADU roof pitch to align with the roof pitch of the primary dwelling). Per IB-111 in Carlsbad, there are only two major transit stops – Carlsbad Village Station or Poinsettia Station. See the one-half mile walking distance map provided by Carlsbad.
• On lots with existing multistory multifamily dwellings (up to 18′ high)
• Attached to the primary home (up to 25′ in height or subject to limits of the applicable zone)

In Carlsbad, building height is measured from the lower point of the existing grade or finished grade, all the way to the highest point of the structure. See code section 21.04.065 Building Height for more detail.

No, roof decks are not permitted on detached ADUs in Carlsbad.

The square footage of any attached ADU may not to exceed 50% of the primary dwelling square footage, or 1,200 sqft, whichever is less, but not less than 800 square feet. ADUs are also required to be 16′ or less in height, attached or detached.

In Carlsbad, the accessory dwelling unit shall be architecturally compatible with the main dwelling unit, in terms of appearance, materials and finished quality.

All information verified by a Carlsbad Associate Planner in March 2022.

Carlsbad currently has no minimum requirement for separation between buildings used for human habitation. Note though that additional fire code requirements will apply when <10′ of separation. Additionally, we recommend at least 4′ of separation for purposes of access and constructability. Further, if either structure includes openings – such as doors or windows – a minimum of 6 feet wall-to-wall separation is required to comply with code.

Verified by a Carlsbad planner via email in May 2024, Section 21.10.080 of the CMC lists the development standards for detached accessory structures containing habitable space. Ordinance No. CS-432 removed the requirement that buildings used for human habitation must be at least 10 feet away from other buildings used for human habitation.

ADUs above garages follow a standard 4′ rear & side setback. For garages attached or detached from the ADU, a 5′ rear & side setback is required per Carlsbad Municipal Code 21.45.090.

As of February 2026, no, Carlsbad no longer requires in-person submission of plans. Their new portal allows submission of digital applications.

Yes, Carlsbad requires soils reports for builds >750SF or with two stories. Builds 500-749SF must include 24” footings and a 5” slab to waive a soils report (<500 SF are exempt entirely).

Yes, accessory dwelling units developed within the coastal zone are subject to the permit requirements of Chapter 21.201 (Coastal Development Permit).

Read more about ADUs in the coastal zone.

In areas within 1/2 mile of public transit, you may be able to stack detached ADUs on top of each other in Carlsbad, as the maximum height allowed in this scenario is 20′. You are also allowed to stack attached ADUs.

We have received different viewpoints on this topic. We are designing & building two stacked ADUs that are attached to the main home.

Yet, per the city of Carlsbad as of Nov 2021, the city has interpreted that multi-family lots are permitted two freestanding, detached accessory dwelling units which are detached from the multi-family residence as well as from one another.

Yes, existing non-livable space may be converted to ADUs (e.g. storage areas and garages). The minimum number of ADU conversions allowed is one, up to a maximum equal to 25% of the number of existing multifamily units. This is in addition to the allowed number of detached ADUs.

If a parking space is required, it may be located within the setbacks and in an existing driveway as tandem parking. Parking spaces don’t need to be replaced when a garage, carport, or covered parking structure is demolished in conjunction with the construction of an ADU or converted to an ADU.