What is a detached ADU?
A detached ADU is a separate building on the same lot as your house, with everything needed to live independently: a kitchen, a full bathroom, a sleeping area and its own entrance. Florida's statute on ADUs (s. 163.31771) describes the same thing: a secondary unit with its own kitchen, bathroom and sleeping area.
How big can a detached ADU be in Miami-Dade?
It depends on the jurisdiction, as of October 2026:
- Unincorporated Miami-Dade (Kendall and similar areas): 400 to 800 sq ft in RU-1 districts, on a lot of at least 7,500 sq ft, and no taller than the main house.
- City of Miami: published summaries of Miami 21 cap the ADU at 10 percent of lot area and no more than 800 sq ft, and never taller than the main house.
- Other cities: each sets its own limits, so we check the code that covers your address.
Why does hurricane code matter so much here?
All of Miami-Dade County sits in the Florida Building Code's High-Velocity Hurricane Zone. A new detached unit needs a structure designed for those wind loads, a roof system and connections that resist uplift, and windows and doors with a Miami-Dade Notice of Acceptance or shutters. See our hurricane code guide.
Does a detached ADU have to be raised for flooding?
If your lot is in a FEMA Special Flood Hazard Area, yes. For A zones, the Florida Building Code puts the lowest floor at or above the base flood elevation plus one foot, or the local design flood elevation if that is higher. A raised slab or stem wall affects the height, the steps to the door and the cost. See our flood zone guide.
Do I need extra parking?
Usually one space. The Miami-Dade County ADU page allows one added space on the property or the adjacent swale. Published summaries of Miami 21 also require one space, except in transit-oriented areas.
When does a detached ADU not fit?
It depends on the yard. A lot under the minimum size, a pool or septic system in the way, or a rear yard too shallow for the setbacks can rule out a detached unit. In those cases an attached suite or an efficiency inside the house may still work. We check before you pay for drawings.
Related
As of October 2026. Sources: Miami-Dade County ADU and guesthouse page; Florida Statutes s. 163.31771; Florida Division of Emergency Management guidance on Florida Building Code flood provisions; published summaries of Miami 21.
Check what your lot allows
Send your address. We check lot size, setbacks and flood elevation before you spend anything on plans.