How Much Does It Cost to Build an ADU in Florida?

The most common question we hear about accessory dwelling units is the simplest one: what will it actually cost? The honest answer is that an ADU is a complete small home — foundation, structure, roof, impact openings, kitchen, bathroom, HVAC, and utilities — and it should be budgeted like one. Below are the typical ranges we see for ADU construction in South Florida, along with the factors that move a project from one end of the range to the other.

Typical ADU Cost Ranges in South Florida

These are typical ranges for permitted, code-compliant work in South Florida. Your lot, design, and finish level will place you within — or occasionally outside — these bands.

A garage conversion is cheapest because the shell already exists. A detached ADU costs the most per square foot because it duplicates everything a house needs — but it also delivers the most privacy, the strongest rental appeal, and the biggest boost to property value.

What Drives the Cost of an ADU

Site work and utilities

Trenching water, sewer, and electrical from the main house — or setting separate meters — can run from a few thousand dollars to tens of thousands depending on distance and whether your street has sewer or you need septic modifications. Lots with mature trees, tight access, or drainage issues add cost before the first block is laid.

Structure and hurricane code

In Miami-Dade and Broward counties, ADUs must meet High-Velocity Hurricane Zone (HVHZ) requirements: impact-rated windows and doors, engineered roof-to-wall connections, and wind-rated roofing. In flood zones, finished-floor elevation requirements can add fill, stem walls, or pilings. These items are non-negotiable under the Florida Building Code, and they are a major reason Florida ADU costs run higher than national averages you see online.

Kitchen and bathroom

Wet rooms are the most expensive square footage in any build. A compact but well-appointed kitchenette and full bath typically account for a quarter or more of the total budget. Our kitchen remodeling team applies the same cabinetry and finish standards to ADU kitchens as to main-house projects.

Finish level

Flooring, cabinetry, lighting, tile, and built-ins can swing the budget by $100+ per square foot between builder-grade and luxury specifications. Most of our clients building a backyard guest house for family or high-end rental choose finishes consistent with the main residence — which protects resale value.

Soft Costs: Design, Permits, and Impact Fees

Beyond construction, plan for:

• Architecture and engineering — site plan, floor plans, structural, MEP drawings
• Permit fees — vary by municipality, typically several thousand dollars
• Impact fees and utility connection charges — vary widely by county and utility
• Survey and soil testing — required for most detached units

As a design-build firm, we carry these phases in-house, which keeps the drawings buildable and the budget honest from day one. See how our process works on our why choose us page.

Where Not to Cut Corners

Every budget has pressure points, but three things should never be value-engineered: the envelope (roof, impact openings, waterproofing), the permits, and the licensed trades. An unpermitted or under-built ADU is a liability at resale, at insurance renewal, and in the first serious storm. Spend where it is structural; save on finishes you can upgrade later.

Cost vs. Return

A properly built ADU produces returns three ways: monthly rental income, appraised value added to the property, and use value for family. For many South Florida homeowners, rental income alone recovers a meaningful share of the investment within a decade — and the unit keeps working after that. We cover the income math in a separate post, and our ADU construction page outlines the full scope we deliver.

Work With Xpert Construction Group

Xpert Construction Group builds ADUs across South Florida with architecture, engineering, permits, and construction under one roof. We are a Florida licensed and insured general contractor (CRC 1335930) with 25+ years of combined experience. Contact us for a free consultation and a realistic budget for your lot.