ADU rules in Miami-Dade County

One accessory unit per lot is permitted in AU, EU, and RU districts (and GU trended to those) inside the Urban Development Boundary; Sec. 33-22(3)(a) states the unit 'may be attached to or detached from the principal dwelling'. A detached unit may not be located in front of or closer to the front lot line than the principal dwelling, may not exceed the principal dwelling's height, and is reviewed as new construction under Ch. 11C. Applies to unincorporated Miami-Dade County, not the City of Miami.

Sec. 33-22(3)(a): 'The accessory unit may be attached to or detached from the principal dwelling.' Construction of an attached accessory unit is reviewed as a substantial improvement under Ch. 11C; an attached unit may have a separate exterior entrance only if it is not visible from a roadway or public right-of-way. Attached units follow the principal dwelling's setbacks and lot coverage.

Sec. 33-22(4)(a) sets minimum lot size and min/max floor area 'in accordance with the CDMP'. The adopting ordinance memo (Ord. 22-146) quotes the CDMP: ADUs 'ranging from 400 to 800 square feet of habitable area are authorized on single-family lots with a minimum area of 7,500 square feet' inside the Urban Development Boundary. The county ADU page confirms 'Must be between 400-800 Sq ft in RU-1 districts' and 'Lot must be a minimum of 7,500 square feet', and adds that a guesthouse exceeding 800 sq ft cannot be used as an ADU. The 2022 memo said a CDMP amendment was under analysis to lower the minimum to 220 sq ft and minimum lot to 5,000 sq ft; the current county page still states 400-800 and 7,500. Guesthouses in EU districts are exempt from these CDMP size limits.

Sec. 33-22 imposes no owner-occupancy requirement for an ADU; the county FAQ states 'The property owner is not required to live onsite. However, if the property owner lives on site, they must reside in the principle dwelling unit and not the ADU or guesthouse.' Only the property owner may obtain the required certificate of use (§33-22(6)(b)). Guesthouses are different: occupancy is limited to the family occupying the principal dwelling, and an owner may not live in the guesthouse and rent out the principal dwelling (§33-22(2)(d), (2)(f)(ii)).

The space must be in a driveway or designated parking area on the property, or on the street/swale directly in front if the property has no driveway or designated area and on-street parking is permitted there. No more than two vehicles may be parked at any one time during the accessory unit's occupancy on the property or on the street/swale directly in front of it. Corridor designations are per the CDMP.

Accessory units 'shall be permitted' by right in AU, EU, RU (and qualifying GU) districts inside the UDB, subject to administrative site plan review, a building permit, and a certificate of use (CU): annually renewable for an ADU, one-time for a guesthouse. No public hearing or conditional-use approval is required. The CU requires occupant names and vehicle plates, annual exterior inspection on renewal, and is denied or revoked for outstanding code fines/liens, false application information, or three fully adjudicated violations in 12 months (three-year ineligibility after revocation). Setback, height, lot coverage, and (to the extent the CDMP allows) minimum lot size adjustments are available administratively under §33-36.1.

Sec. 33-22(2)(f): the accessory unit may not be sold separately from the principal dwelling; an ADU may be rented for a fee only if the rental period is not less than one month; a guesthouse may not be rented separately (gratuitous guests only, limited to the principal dwelling's family). Sec. 33-28(14): where a property has an accessory unit, the entire property (principal dwelling plus accessory unit) may operate as a single vacation rental, but neither may be a vacation rental separate from the other. Overnight occupancy is capped at two persons per bedroom (excluding children under three), and occupant names must be kept current on the annually renewable certificate of use.