What Is an ADU? The Complete Florida Guide

If you own a home in South Florida, you have probably heard the term ADU more often in the last few years than in the previous two decades combined. An accessory dwelling unit — a self-contained second home on a single-family lot — has become one of the smartest ways for Florida homeowners to add living space, generate rental income, or keep family close without moving. This guide explains exactly what an ADU is, what forms it can take, and what it takes to build one properly.

What Counts as an Accessory Dwelling Unit

An ADU is a complete, independent living space located on the same lot as a primary residence. To qualify as a true dwelling unit — not just a bonus room — it needs its own entrance, a full bathroom, a kitchen or kitchenette, and a sleeping area. Depending on the municipality, you may see ADUs called guest houses, in-law suites, granny flats, casitas, or carriage houses. The label varies; the legal definition is what matters when you apply for permits.

ADUs generally fall into three categories:

• Detached ADU — a stand-alone backyard structure, the most private and most valuable option
• Attached ADU — an addition connected to the main house with its own separate entrance
• Conversion ADU — an existing garage or enclosed space converted into a legal dwelling

Each path has different costs, timelines, and code implications, which we compare in detail across our blog and on our ADU construction service page.

Why Florida Homeowners Are Building ADUs

The surge in ADU construction in Florida is driven by simple math and changing households:

1. Rental income. A well-built one-bedroom ADU in Broward, Miami-Dade, or Palm Beach counties can command strong monthly rent, helping offset a mortgage.
2. Multigenerational living. Aging parents or adult children get independence and proximity at once.
3. Property value. A legal, permitted second dwelling adds meaningful resale value to a single-family lot.
4. Flexibility. Home office, gym, studio, guest quarters — the space adapts as your life changes.

What Florida Law Says About ADUs

Florida state law encourages ADUs as a partial answer to the housing shortage, but the specific rules — maximum size, setbacks, parking, and whether you can rent the unit — are set at the county and city level. Fort Lauderdale, Miami, and many other South Florida municipalities now permit ADUs on most single-family lots, subject to zoning review. Before sketching floor plans, you need a professional to confirm your lot's zoning district, setbacks, and lot coverage limits. As a design-build firm, we handle that feasibility research, the architecture, and the ADU permits as one integrated process rather than leaving you to coordinate separate consultants.

What It Costs to Build an ADU in South Florida

Every lot and design is different, but typical ranges in South Florida run from the low six figures for a straightforward garage conversion to $250,000–$450,000+ for a fully detached, hurricane-rated backyard guest house with premium finishes. Site conditions, utility connections, impact fees, and finish level drive most of the variance. Because an ADU is a complete small home — foundation, roof, impact windows, kitchen, bath, HVAC — it should be budgeted like one, not like a shed. Our FAQ page covers common budgeting questions, and our cost-focused posts break the numbers down line by line.

Building to Florida's Standards

Any ADU in South Florida must meet the Florida Building Code, and in Miami-Dade and Broward counties that means the High-Velocity Hurricane Zone (HVHZ) provisions — the strictest wind standards in the country. Impact-rated windows and doors, engineered roof connections, and proper flood-zone elevation are not upgrades; they are requirements. This is where an experienced general contractor earns their fee. Xpert Construction Group is a Florida licensed and insured contractor (CRC 1335930) with 25+ years of combined hands-on experience building to these standards, from custom homes to home additions and detached ADUs.

Is an ADU Right for Your Property?

Ask three questions. First, does your lot have the zoning and physical room for the unit type you want? Second, does the budget make sense against your goals — rental income, family housing, or long-term value? Third, do you have a builder who can take the project from feasibility through final inspection without handing you off between firms? If the answer to all three is yes, an ADU is one of the highest-utility investments you can make in a Florida property. You can see examples of our recent work in our portfolio.

Work With Xpert Construction Group

Xpert Construction Group designs and builds ADUs across South Florida as a true design-build partner — architecture, engineering, permits, and construction under one roof. We are licensed and insured (Florida CRC 1335930). Contact us for a free consultation and a straight answer on what your lot allows.