The backyard casita is having a moment. Rising home prices, multigenerational households, and rental income potential have made accessory dwelling units — detached guest houses, in-law cottages, backyard studios with a kitchen and bath — one of the most requested projects in South Florida. Here is what it actually takes to build one in Miami-Dade and Broward: the zoning reality, the construction process, and the numbers that shape the decision.
First Question: Is It Allowed on Your Lot?
ADU rules vary dramatically by municipality and zoning district. Some South Florida jurisdictions permit detached units with a kitchen on single-family lots under specific conditions; others allow “guest houses” without full kitchens, restrict rentals, cap square footage relative to the main home, or prohibit them in certain districts entirely. Setbacks, lot coverage limits, height caps, and parking requirements all apply. Step one is a zoning determination for your specific address — before design, before pricing, before dreaming too specifically. Our sister company IG Permit Expeditors runs these checks routinely.
Attached, Detached, or Converted?
Three paths reach a similar outcome: a fully detached new structure (most flexible, most expensive), an attached addition with separate entrance (shares structure and utilities), or a conversion of existing space — which is where garage conversions come in. Detached units require their own foundation, roof, and utility connections; conversions reuse the envelope but inherit its constraints. Cost and timeline follow that logic.
The Construction Reality
A detached ADU is a small house, and it gets built like one: engineered foundation, wind-rated structure to the High-Velocity Hurricane Zone standard, impact windows and doors, full electrical service (often a subpanel from the main house), plumbing tied into the main sewer line or septic evaluation, HVAC, and a complete interior. Utility runs from the house to the unit are a recurring cost surprise — distance matters. Permitting covers building, electrical, plumbing, mechanical, and zoning review, with inspections at every stage.
What It Costs, Honestly
Small buildings cost more per square foot than large ones — a kitchen and bathroom are expensive regardless of the room count around them. A detached ADU in South Florida commonly runs from the low six figures upward depending on size, finishes, site work, and utility distance; a garage conversion lands well below that. The right way to budget is scope-first: decide what the unit must do (rental income, family housing, home office) and size and finish it to that job.
Rental Income and Resale
Where rentals are permitted, an ADU can materially offset its cost; where they are not, the unit still adds usable square footage and multigenerational flexibility that buyers increasingly seek. Verify short-term versus long-term rental rules for your municipality before assuming income — the rules are local and enforced.
Timeline
Zoning confirmation and design front-load the calendar; permitting for a new structure takes longer than for interior work; construction on a detached unit typically runs several months. Plan on a project measured in seasons, not weeks — and worth it when the family or the tenant moves in.
Thinking About a Casita?
IG Construction designs and builds detached ADUs, guest houses, and conversions across Miami-Dade and Broward, with zoning checks and permits handled up front. Call (305) 686-9919 or request a free consultation.