What is the Miami 21 code?

Miami 21 was one of the first form-based zoning codes in a major US city. Instead of segregating "residential" from "commercial," it regulates the PHYSICAL CHARACTER of development — building height, setbacks, massing, frontage type, and how the building meets the street.

Transect Zones (the backbone of Miami 21):

• T3 — Sub-Urban — lowest intensity. Single-family and duplex. Wide setbacks. Detached houses, front yards.
• T4 — General Urban — more compact. Small-scale apartments, rowhouses, detached houses in tighter configurations.
• T5 — Urban Center — neighborhood main streets. Mixed-use buildings. Retail frontage.
• T6 — Urban Core — downtown. Tallest buildings, densest use, full mixed-use.
• CI — Civic Institutional — schools, hospitals, public buildings.
• D — District — specialized areas (medical, port, industrial).
• CS — Civic Space — parks, plazas, public open space.

Each transect zone specifies:

• Setbacks.
• Height (measured in stories + feet).
• Lot coverage.
• Building types allowed.
• Frontage types allowed (stoop, porch, shopfront, etc.).
• Required elements (e.g., porches in T3 residential).

Why Miami 21 matters for remodel/addition:

• Additions must respect your lot's transect zone setbacks.
• Some transect zones have design review for exterior alterations.
• Historic overlay (Miami-Dade HEPB for County, City Historic Preservation Office for City) applies on top of Miami 21 in designated districts.

Common residential homeowner questions under Miami 21:

• "Can I add a second story?" — yes in most transect zones; must respect height limit (varies by zone, T3 limited to 2 stories; T4-T6 allow more).
• "Can I build an ADU?" — ADUs ("accessory dwelling units") are allowed in some transect zones with specific rules; Florida doesn't have California-style state-preemptive ADU law.
• "Can I convert my garage?" — depends on setback and frontage rules; garage conversions in T3 often require variances.
• "What's my setback?" — look up your property at zoning.miamigov.com; your zone is listed and setbacks tabulated.

Outside City of Miami:

• Miami Beach has its own zoning code (traditional).
• Coral Gables has its own code and Historic Preservation Office.
• Miami-Dade County unincorporated areas use the County code.

HVHZ overlay:

• Regardless of zoning, all Miami-Dade work is in the High-Velocity Hurricane Zone, with specific Florida Building Code requirements for wind resistance.

AskBaily's Miami scoping identifies your transect zone, applicable setbacks, HVHZ requirements, and any historic overlay. See /miami and /compare/angi-miami for deeper local context.