How to Get an ADU Permit in Miami: Complete 2025 Guide

Insights

November 3, 2025

minute read

Key Takeaways

Miami-Dade County requires both a building permit and an annual Certificate of Use for ADUs, with 171,683 single-family properties now eligible under 2022 reforms
ADUs are only permitted on properties with a minimum lot size of 7,500 square feet within the Urban Development Boundary in designated zoning districts (AU, EU, RU, and GU)
Dwelling size must be between 400-800 square feet in RU-1 districts with a minimum habitable area of 220 square feet
Permit costs are valuation-based per Miami-Dade's Building Fee Schedule; for a small ADU, total County permit fees often fall within roughly $1,500–$3,000, but actual costs vary by scope and valuation
All ADUs must meet Miami-Dade's strict hurricane-resistant codes for High Velocity Hurricane Zones with materials that withstand extreme wind loads
Pre-approved ADU designs streamline the permitting process compared to custom designs, with plans already reviewed by the building department
Mesocore's modular ADU solution includes factory-installed MEP systems certified by Intertek; for modules approved under Florida's DBPR modular program, factory inspections can cover MEP rough-ins within the unit, while local inspectors typically focus on foundations, site connections, and any on-site work, and featuring a 180 mph wind rating engineered to comply with Florida Building Code HVHZ requirements in Miami-Dade

Miami-Dade County transformed its ADU regulations in November 2022, creating a legal pathway for homeowners to add rental units or family housing on their properties. The new ordinance aims to help people find housing and keep people in their homes amid rising costs and an affordable housing shortage. Unlike guesthouses that cannot be rented, ADUs offer income-generating potential with monthly rental rates ranging from $1,000 to $1,800 in Miami.

The permitting process requires navigating building department reviews, Certificate of Use applications, and strict compliance with hurricane codes. For homeowners seeking a turnkey solution, Mesocore's Model E provides a 410-square-foot hurricane-rated unit engineered to meet or exceed Miami-Dade's HVHZ standards with a 180 mph wind rating and factory-tested systems.

What is an ADU and Why Miami Homeowners Are Building Them

An Accessory Dwelling Unit is an attached or detached accessory building used as an ancillary residential unit located on the same lot as the principal single-family dwelling, with a separate kitchen, bathroom, and sleeping area, intended for use by a separate family of occupants.

Miami-Dade County distinguishes between ADUs and guesthouses based solely on rental eligibility. There is no physical difference between the two—a guesthouse is not for rent while an ADU can be rented out, but never for less than one month. Under no circumstances can either be used for vacation rentals such as Airbnb.

Common ADU Types in Miami-Dade County

Miami-Dade permits both attached and detached ADUs:

Detached ADUs: Separate structures in the backyard, commonly converted garages or purpose-built cottages
Attached ADUs: Units within or connected to the main house with separate entrances
Garage conversions: The ordinance accommodates garage conversions, reducing the minimum lot area to 5,000 square feet for these specific projects

Financial Benefits of Adding an ADU

The County ordinance aims to provide additional income for homeowners, helping them offset rising costs and stay in their homes longer while offering housing options for adult children or elderly family members. Commissioner Eileen Higgins explained, "This won't just" help people find housing, it will help keep people in their homes."

Miami's rental income potential is about $3,100 per month, providing substantial financial relief for homeowners facing rising property taxes and insurance costs. For families, ADUs create space for multigenerational living while maintaining privacy and autonomy.

Miami-Dade County ADU Zoning and Property Requirements

Geographic and dimensional restrictions determine which properties qualify for ADU construction before any design or permitting work begins.

Eligible Zoning Districts and Location Requirements

One accessory unit per lot shall be permitted in the following zoning districts located inside of the Urban Development Boundary: AU, EU, and RU, as well as GU for properties that are trended to AU, EU, or RU.

This is a critical restriction—the ordinance does not apply to houses within municipalities. Properties located in incorporated cities like Miami, Coral Gables, or Hialeah must follow their own local ADU rules, which may be more restrictive or have different requirements.

Property owners can obtain zoning information by visiting Miami-Dade Land Management, which allows you to look up zoning classification, hearings, density, and approved land uses.

Minimum Lot Size and ADU Dimensions

Lot size must be a minimum of 7,500 square feet, and the dwelling size must be between 400-800 square feet in RU-1 districts. The ordinance mandates a minimum habitable area of 220 square feet, accommodating garage conversions and reducing the minimum lot area to 5,000 square feet for these specific projects.

For homeowners considering modular ADU solutions, Mesocore's 410-square-foot Model E ADU fits comfortably within Miami-Dade's 400-800 square foot range while maximizing livable space through efficient design.

Parking and Site Requirements

ADUs require parking compliance per zoning district; verify swale parking allowances and applicable setbacks with County zoning or the ADU page. ADUs require a maximum of one additional parking space and not more than two vehicles.

Understanding Miami-Dade Building Code for ADUs

Miami-Dade County enforces strict hurricane-resistant codes, making it essential for the materials used to withstand high-velocity hurricane zones.

High Velocity Hurricane Zone (HVHZ) Standards

Miami-Dade and Broward Counties are the only Florida counties designated as High Velocity Hurricane Zones. All ADU construction must use materials and methods designed for extreme wind events. Building codes determine the safety, design, construction materials, and labor practices.

All construction work is generally required to be performed by licensed contractors in Miami-Dade County. However, Florida's owner-builder exemption may allow certain homeowners to act as their own contractor if they meet statutory requirements. Confirm eligibility with Miami-Dade before proceeding. Regular inspections throughout the construction phase affirm that the ADU meets or exceeds the established standards.

Foundation and Structural Requirements

ADUs require engineered foundations designed for hurricane loads, typically concrete pier or slab-on-grade systems depending on the structure type and site conditions. All structural elements must be engineered and sealed by a Florida-licensed professional engineer to meet HVHZ requirements.

Mesocore's Model E ADU uses a concrete pier foundation with 8 piers, providing the required structural integrity while simplifying site preparation compared to full slab foundations.

Step-by-Step ADU Permit Application Process in Miami

Miami-Dade's permitting process involves multiple phases, from initial feasibility verification through final Certificate of Use approval.

Step 1: Verify Property Eligibility

Start by visiting Miami-Dade Land Management to determine your zoning classification, hearings, density, and approved land uses. Confirm your property:

Is in unincorporated Miami-Dade County (not within a municipality)
Falls within the Urban Development Boundary
Is zoned AU, EU, RU, or GU trending to these zones
Meets the 7,500 square foot minimum lot size requirement

The most common mistake is assuming all Miami-Dade properties are eligible—properties in incorporated municipalities or outside eligible zoning districts cannot build ADUs under the County ordinance.

Step 2: Choose Between Pre-Approved or Custom Design

Miami-Dade County created a pre-approved ADU program that streamlines the building permitting process to add a dwelling unit to your home through browsing pre-approved ADU designs that have been submitted by design firms.

Pre-approved plans can shorten review by using designs already reviewed by the County; however, site-specific reviews (zoning, setbacks, foundation, wind/flood parameters, utilities) are still required.

Pre-Approved ADU Blueprint Program:

Browse the catalog of pre-approved designs varying in size, type, and style
Review images and details to find one suitable for your needs and site
Connect with designer through the contact information provided
Designer guides you through the permitting process and shares the fee to use their design

Custom Design Option:

Hire a private architect or engineer to design an ADU plan specific to your needs
Plans must be drawn-to-scale and sealed by Florida-licensed professionals
Longer permitting timeline compared to pre-approved designs

For homeowners seeking streamlined permitting with built-in hurricane compliance, Mesocore offers professional site plan services for $200 refundable deposit to create a site plan that confirms feasibility and determines whether it meets local zoning and setback requirements.

Step 3: Prepare Required Documentation

You will submit one set of drawn-to-scale plans showing all the work on the property to be reviewed and approved by all required disciplines. At minimum, the plans should include:

Site plan showing ADU location, setbacks, and existing structures
Building floor plan and finish floor elevation
Sufficient detail of any structural, electrical, mechanical, plumbing and roofing components

Critical requirements:

A completed ADU owner disclosure statement is required for all ADU applications
Pre-Approved ADU Hold Harmless Form
Professional engineer seals on all structural, electrical, plumbing, and mechanical plans

Step 4: Submit Building Permit Application

Initially, an application must be submitted to the local building department, detailing the project scope and demonstrating adherence to zoning laws. Upon review, if the application meets all the criteria, the necessary permits are issued.

To construct an ADU or legalize an ADU, a building permit is required. Applications are submitted through the Plan Submission Portal.

Miami-Dade County offers free Homeowners Permitting Assistance services to assist individuals navigating the application process.

Step 5: Obtain Certificate of Use After Construction

The County ordinance requires all ADUs to acquire a Certificate of Use after completion and before occupying the ADU, and the CU will need to be renewed annually.

This represents a key difference from guesthouses: A certificate is required for each accessory unit and this certificate must be renewed every year at which time the unit will be inspected, while guesthouses are only required a one-time CU that does not need to be renewed.

You may apply for a Certificate of Use via the Plan Submission Portal. For consultation, register and create an account through the online registration system (MeetQ) to consult with staff. Consults may be scheduled in person, by phone or virtually on specified days and times.

Required Documents and Plans for Miami ADU Permits

Complete documentation prevents delays and rejections during the review process.

Essential Permit Documents

A checklist of regulatory requirements for ADU projects typically includes:

Ensuring zoning compliance to confirm the property is suitable for an ADU
Verifying design compatibility with existing structures or neighborhood aesthetics
Acquiring the necessary permits from local authorities

Building Permit Application Package:

Completed building permit application form
ADU owner disclosure statement (mandatory)
Pre-Approved ADU Construction Plans Hold Harmless Form (if using pre-approved design)
Proof of property ownership
Site plan drawn to scale

Engineering and Architectural Plans

All plans must be sealed by Florida-licensed professionals and include:

Architectural drawings: Floor plans, elevations, cross-sections
Structural plans: Foundation design, framing details, hurricane tie-down specifications
Electrical plans: Service panel, circuit layout, fixture locations
Plumbing plans: Water supply, drainage, fixture placement
Mechanical plans: HVAC system design and equipment specifications

Mesocore's factory-built approach simplifies this documentation phase. The Model E ADU includes an approved set of engineered construction drawings with all plumbing and electrical installed and tested in the factory before shipping, reducing the complexity of plan reviews.

Survey and Property Documentation

A current property survey showing:

Property boundaries and dimensions
Existing structures and their locations
Proposed ADU placement with setback measurements
Easements and restrictions

Miami-Dade ADU Permit Costs and Fees Breakdown

Understanding the complete cost picture helps homeowners budget accurately for ADU projects.

Building Permit and Application Fees

Critical financial components of ADU projects encompass:

Construction costs: Materials, labor, and associated expenses such as site preparation
Permitting fees: Costs of obtaining necessary approvals and licenses from local authorities
Potential cost overruns: Unforeseen circumstances or changes in project scope that may lead to increased expenses

Design and Engineering Costs

If using pre-approved designs, the designer guides you through the permitting process and shares the fee to use their design. Fees vary by designer with custom design costs being higher depending on complexity.

Additional Fees and Costs

Certificate of Use application: Initial application and annual renewal fees
Utility connection fees: Water, sewer, and electrical hookups
Impact fees: Potential land impact fees depending on jurisdiction
Site preparation: Grading, tree removal, soil testing
Foundation installation: Concrete piers or slab preparation

For detailed cost planning, homeowners should explore financing options for ADU construction, including home improvement loans, HELOCs, and specialized ADU lending programs.

Working with Contractors and Construction Requirements

Licensed professionals are generally required for ADU construction in Miami-Dade County to ensure safety and code compliance.

Contractor Licensing Requirements

Hold valid Florida contractor licenses for their trade
Carry liability insurance
Provide workers' compensation coverage
Register with Miami-Dade County Building Department

Inspection Requirements

Regular inspections throughout the construction phase affirm that the ADU meets or exceeds the established standards. Traditional site-built construction requires multiple inspections:

Foundation inspection before concrete pour
Framing inspection after structure is complete
Rough plumbing, electrical, and mechanical inspections
Insulation and weatherproofing inspection
Final building, electrical, plumbing, and mechanical inspections

Mesocore's Inspection Advantage: For modules approved under Florida's DBPR modular program, factory inspections can cover MEP rough-ins within the unit; local inspectors typically focus on foundations, site connections, and any on-site work. Requirements remain subject to the local authority having jurisdiction. Total inspection requirements are reduced and construction timelines accelerate as a result in Mesocore ADUs.

Utility Connections and Infrastructure Requirements for Miami ADUs

ADUs require connection to water, sewer, and electrical systems, with specific considerations for Miami-Dade properties.

Water and Sewer Connections

ADUs must connect to municipal water and sewer systems where available. In areas with septic systems, homeowners commonly ask: Can my ADU be connected to my existing septic system?

In most cases you can connect to your existing septic as long as it is large enough to handle additional plumbing. This will be determined during the feasibility review process.

Electrical Service Requirements

ADUs can be connected to the main house electrical service if adequate capacity exists, or may require a separate meter and service panel. Load calculations by a licensed electrician determine the appropriate approach.

Mesocore's Off-Grid Option: Each Mesocore unit includes a 6 kW solar array with two 10 kWh lithium-ion batteries for energy storage. Mesocore reports prior approvals for off-grid operation in some Florida jurisdictions; verify with Miami-Dade officials for local applicability. This off-grid capability might cut connection fees, meter costs, and ongoing utility expenses while maintaining full functionality, though verification with Miami-Dade building officials is recommended.

Common ADU Permit Mistakes to Avoid in Miami-Dade

Understanding frequent errors helps applicants navigate the process smoothly.

Why ADU Permits Get Rejected

The most common reasons for permit denials include:

Wrong jurisdiction: Applying for County ADU permits when property is within a municipality
Ineligible zoning: Property not in AU, EU, RU, or GU districts
Insufficient lot size: Property under 7,500 square feet (or 5,000 for garage conversions)
Size violations: ADU exceeding 800 square feet or under 400 square feet
Incomplete plans: Missing required engineering seals or documentation
Rental violations: Planning short-term rentals under one month

Documentation Errors That Delay Approval

Each step in the permitting process can be accompanied by a variety of fees and bureaucratic processes that may delay project timelines. Common documentation issues include:

Missing ADU owner disclosure statement
Plans lacking professional engineer seals
Incomplete site plans missing setback dimensions
Failure to show compliance with hurricane codes

How to Avoid Costly Revisions

Use pre-approved designs when possible to reduce review cycles
Hire professionals familiar with Miami-Dade ADU requirements
Schedule pre-application consultations with building department staff
Submit complete documentation packages with all required forms and seals
Verify all measurements and calculations before submission

For homeowners new to construction permitting, consider working with experienced ADU contractors who understand Florida building codes and Miami-Dade's specific requirements.

Legalizing Unpermitted Existing ADUs

Many Miami-Dade properties have existing unpermitted structures that could potentially be legalized as ADUs.

Process for Legalization

The process to legalize work without a permit is the same as applying for new project. You will be required to submit one set of drawn-to-scale plans showing all the work on the property to be reviewed and approved by all required disciplines.

Legalization requirements:

Structure must meet current building codes including HVHZ standards
All work must be brought up to code, potentially requiring significant renovations
Professional engineering evaluation to confirm structural integrity
Full permitting process including inspections
Certificate of Use application and annual renewals

The legalization path can be costly if significant code upgrades are needed, but provides legal protection and the ability to legally rent the unit.

Where to Find Hurricane-Rated ADUs and Turnkey Solutions in Miami

Miami-Dade's strict hurricane codes make factory-built, pre-engineered ADU solutions particularly attractive for homeowners seeking reliable compliance.

Benefits of Modular ADUs in Hurricane Zones

Pre-engineered modular ADUs offer several advantages:

Factory-built construction with quality control testing
Pre-certified compliance with hurricane wind loads
Faster installation compared to site-built construction
All MEP systems factory-installed and tested
Reduced on-site inspection requirements

Mesocore's Hurricane-Resistant ADU Solution

For Miami-Dade homeowners seeking a turnkey approach, Mesocore's Model E is engineered to meet or exceed Florida Building Code, including HVHZ standards in Miami-Dade and Broward. Key features include:

180 mph wind rating engineered to comply with Florida Building Code HVHZ requirements in Miami-Dade
Designed to IBC/FBC standards and registered in the Florida DBPR modular home program
Factory-installed MEP systems certified by Intertek before delivery
Hurricane impact windows and doors as standard
6-KW solar system with lithium-ion battery storage
Robotically welded steel providing exceptional structural strength
On-site installation in as little as 10 days once permits are obtained

Starting at $129k factory MSRP (price subject to change), the Model E ADU includes features that would cost significantly more if purchased separately, while the integrated design simplifies Miami's complex permitting process. The unit ships as a 20-foot ISO-certified container, making delivery straightforward even to urban Miami lots.

Why Mesocore Streamlines Miami-Dade ADU Permitting

Navigating Miami-Dade's ADU permitting process presents unique challenges that Mesocore's modular approach directly addresses.

Factory-Installed Systems Reduce Inspection Complexity

Traditional ADU construction requires multiple inspection phases for rough-in plumbing, electrical, and mechanical systems. Mesocore eliminates this complexity through factory installation. For modules approved under Florida's DBPR modular program, factory inspections can cover MEP rough-ins within the unit; local inspectors typically focus on foundations, site connections, and any on-site work. This reduces total inspection requirements and accelerates construction timelines.

Hurricane Compliance Built In

Miami-Dade's HVHZ requirements demand extensive engineering documentation for wind resistance. Mesocore's 180 mph wind rating is engineered to comply with Florida Building Code HVHZ requirements in Miami-Dade, with the steel core structure specifically engineered for Florida's hurricane conditions. The approved set of engineered construction drawings provided with each unit simplifies the permit documentation process compared to custom designs.

Off-Grid Capability Provides Unique Advantages

Each Mesocore ADU includes a 6 kW solar system with two 10 kWh lithium-ion batteries. While Miami-Dade doesn't require solar, this integrated system offers benefits that matter for permitting and operations. Mesocore reports prior approvals for off-grid operation in some Florida jurisdictions; verify with Miami-Dade officials for local applicability. Where approved, the off-grid capability means no separate utility meter required, potential elimination of utility connection fees, and zero ongoing electric bills that maximize rental income.

The combination of factory certification, hurricane engineering, and integrated utilities makes Mesocore particularly well-suited for Miami-Dade's complex regulatory environment. Homeowners gain a streamlined permitting path while meeting all code requirements.

Frequently Asked Questions

How much does an ADU permit cost in Miami-Dade County?

Permit fees are valuation-based per Miami-Dade's Building Fee Schedule; for a small ADU, total County permit fees often fall within roughly $1,500–$3,000, but actual costs vary by scope and valuation. Total costs including design, engineering, Certificate of Use fees, and utility connections typically range from $5,000-$15,000+ depending on project complexity and whether you use pre-approved or custom designs.

How long does it take to get an ADU permit approved in Miami?

The timeline varies based on design approach and application completeness. Pre-approved designs result in quicker permitting process compared to starting from scratch, typically 2-4 months from application to permit issuance. Custom designs may take 4-6 months or longer if revisions are needed.

Can I connect my ADU to my existing septic system in Miami?

In most cases you can connect to existing septic as long as it is large enough to handle additional plumbing. This will be determined during the feasibility review process. A septic system evaluation may be required to confirm adequate capacity.

Are ADUs allowed in all Miami-Dade residential zones?

No. ADUs are only permitted in specific zoning districts (AU, EU, RU, and GU trending to these zones) located inside the Urban Development Boundary in unincorporated Miami-Dade County. Properties within incorporated municipalities must follow their own local ADU rules, and the County ordinance does not apply to houses within municipalities.

What are the setback requirements for ADUs in Miami-Dade County?

ADUs require parking compliance per zoning district; verify swale parking allowances and applicable setbacks with County zoning or the ADU page. Specific measurements vary by zoning district, which is why verification through Miami-Dade Land Management and consultation with the building department is essential during the feasibility phase.

Do I need a licensed contractor to build an ADU in Miami-Dade?

All construction work is generally required to be performed by licensed contractors in Miami-Dade County. However, Florida's owner-builder exemption may allow certain homeowners to act as their own contractor if they meet statutory requirements. Confirm eligibility with Miami-Dade before proceeding. This includes general contractors for overall construction management and licensed trade contractors for electrical, plumbing, and mechanical work. All work must be inspected and approved by Miami-Dade building inspectors.

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