ADU Rules in Miami, FL (2026)
ADU rules, permit requirements, size limits, and fees for Miami, FL. Source-cited from official municipal code.
Yes, ADUs are allowed in Miami, FL.
Miami, FL permits accessory dwelling units (ADUs) on residential properties. ADUs — also called granny flats, in-law units, backyard cottages, or secondary suites — are secondary housing units on a single-family or multifamily lot. State and local law actively preempts local restrictions, making ADU approval a streamlined ministerial process. In Miami, the City of Miami Building Department handles ADU permit applications. Below you will find the current size limits, setbacks, fees, and timeline for building an ADU in Miami.
ADU Size Limits
ADU Size Limits in Miami: Detached ADU: up to 750 sqft or 50% of primary structure, whichever is less (max height: 2 stories). Attached ADU: 50% of primary structure square footage. Miami 21 Code Section 3.3 governs accessory structures and dwelling units. Under T3 zoning, a Carriage House (detached ADU) may be built in rear of lot. Sizes vary by Transect Zone — T3 lots are most common for detached ADUs. HB 1339 (2024) requires cities to allow ADUs without being more restrictive than state baseline standards.
| Type | Max Size | Max Height |
|---|---|---|
| Detached ADU | 750 sqft or 50% of primary structure, whichever is less | 2 stories |
| Attached ADU | 50% of primary structure square footage | Same as main structure per Transect Zone |
Permit Fees
ADU Permit Fees in Miami: Plan check fee: $500–$2,500. Building permit fee: Based on construction value — typically $1,500–$5,000. Impact fees: Capped at single-family rate per Florida HB 1339 (2024) — previously $5,000–$15,000; now reduced. School fees: Miami-Dade County school impact fee applies — approximately $3,000–$5,000 for residential units. Total estimated permit cost: $5,000–$15,000 total permit fees depending on size and scope. Florida HB 1339 (2024) caps ADU impact fees at the same rate as single-family homes, which significantly reduced costs. Miami-Dade County impact fees apply in addition to City of Miami permit fees. Fee schedule: https://www.miamigov.com/Government/Departments-Organizations/Building
| Fee Type | Amount |
|---|---|
| Plan Check | $500–$2,500 |
| Building Permit | Based on construction value — typically $1,500–$5,000 |
| Impact Fees | Capped at single-family rate per Florida HB 1339 (2024) — previously $5,000–$15,000; now reduced |
| School Fees | Miami-Dade County school impact fee applies — approximately $3,000–$5,000 for residential units |
| Total Estimate | $5,000–$15,000 total permit fees depending on size and scope |
Permit Timeline
Miami ADU Permit Timeline: Ministerial approval required per Florida HB 1339 — no discretionary review for ADUs meeting objective standards. Miami Building Department typically processes ADU permits in 4-8 weeks for plan check. Construction typically 4-12 months. Apply through the City of Miami Building Department online permit portal. Phone: (305) 416-1100.
Setback Requirements
ADU Setback Requirements in Miami: Front setback: follows zone standard. Side setback: 5 feet. Rear setback: 5 feet. Miami 21 T3 zone setbacks apply to accessory structures. Carriage Houses in T3 must be set back from rear lot line. Side setbacks of 5 feet typically required. Front of accessory structure must be behind rear of principal building. State law under HB 1339 (2024) prohibits more restrictive setbacks than applicable to primary dwellings.
Parking Requirements
Parking Requirements: No additional parking required for ADUs near transit per Florida HB 1339 (2024). Miami-Dade Transit's Metrorail and Metromover provide extensive transit access in urban areas. ADUs in T3 zones typically require 1 space unless within one-half mile of a transit stop per state law.
Restrictions & Requirements
- ADU must comply with Miami 21 Transect Zone standards for the property
- Carriage House (detached ADU) in T3 zones must be accessed from rear lane or alley when available
- ADU cannot be sold separately from primary lot under standard subdivision rules
- Short-term rental of ADU requires compliance with Miami-Dade STR regulations
- Historic districts (e.g., Coconut Grove, Little Havana) may require additional design review
- ADU must have permanent foundation — no recreational vehicles or mobile homes
How Many ADUs Are Allowed?
Number of ADUs Allowed in Miami: Single-family lots: 1 ADU (Carriage House) per T3 lot; additional units may be permitted under T4+ zoning. Multifamily properties: Varies by Transect Zone — T4 and above permit multiple dwelling units by right. Miami 21 T3 (Sub-Urban) zone is the primary single-family transect — 1 Carriage House/ADU permitted in rear. Florida HB 1339 (2024) does not cap ADU counts to 1 per lot for all cases. T4, T5, T6 zones allow multiple units by design of the transect system.
Single-Family Lots
1 ADU (Carriage House) per T3 lot; additional units may be permitted under T4+ zoning
Multifamily Properties
Varies by Transect Zone — T4 and above permit multiple dwelling units by right
State Law & Preemption
State Preemption: Florida HB 1339 (2024) preempts local ADU restrictions — eliminates owner-occupancy requirements statewide, caps impact fees, requires ministerial approval for code-compliant ADUs. Florida Live Local Act (SB 102, 2023) also applies and prevents municipalities from restricting multifamily in commercial zones where residential is permitted.
Historic District Considerations
Historic District Requirements: Miami has 8 historic districts where additional design review may be required for ADU construction. Design review approval is required before obtaining a building permit for properties in historic overlay zones. City of Miami has 8 locally designated historic districts including Coconut Grove, Little Havana Arts District, Wynwood Arts District, and others. Historic Preservation Board reviews exterior changes to contributing structures. Additionally, Miami Beach (separate municipality) contains the internationally known Miami Beach Architectural Historic District (Art Deco). Design review required for alterations in City of Miami historic districts. Certificate of Appropriateness required. Look up historic district boundaries at: https://www.miamigov.com/Government/Departments-Organizations/Planning
Frequently Asked Questions
Can I build an ADU in Miami?
Yes. Miami, FL allows accessory dwelling units. On a single-family lot you can build 1 ADU (Carriage House) per T3 lot; additional units may be permitted under T4+ zoning.
How big can an ADU be in Miami?
The maximum size for a detached ADU in Miami is 750 sqft or 50% of primary structure, whichever is less square feet.
How long does it take to get an ADU permit in Miami?
The typical ADU permit timeline in Miami is Ministerial approval required per Florida HB 1339 — no discretionary review for ADUs meeting objective standards. Miami Building Department typically processes ADU permits in 4-8 weeks for plan check. Construction typically 4-12 months.. Total estimated permit fees are $5,000–$15,000 total permit fees depending on size and scope.
Do I need extra parking for an ADU in Miami?
No, Miami does not require additional parking for ADUs.
Do I have to live on-site to have an ADU in Miami?
No, owner-occupancy is not required for ADUs in Miami.
Source: Miami 21 Zoning Code (Ordinance 13114, as amended); Florida Statutes 166.0451 (HB 1339, 2024). Last verified April 5, 2026. View source