What an ADU Costs in Palm Beach County: The Real Ranges
An accessory dwelling unit in Palm Beach County costs anywhere from $45,000 for a basic garage-to-living-space conversion to $220,000+ for a fully detached, code-built unit with its own foundation, roof, and utility connections. The single biggest variable isn't finish level — it's whether you're converting existing structure or building new from the ground up.
Generic national ADU cost guides quote $100,000–$300,000 averages that don't reflect what a garage conversion actually costs here, and they don't account for Palm Beach County's specific impact fee schedule or the zoning differences between unincorporated county land and the county's 39 municipalities.
| ADU Type | Typical Cost (Palm Beach County) | What Drives the Price |
|---|---|---|
| Garage Conversion (attached) | $45,000–$95,000 | Existing slab & structure reused, HVAC extension, egress window, bathroom/kitchenette plumbing, insulation upgrade |
| Garage Conversion (detached) | $55,000–$110,000 | Same scope plus new utility service run from the main house or a new meter |
| Detached ADU — Modular/Prefab | $95,000–$160,000 | New foundation, site prep, factory-built unit, crane set, utility hookups, impact fees |
| Detached ADU — Site-Built | $140,000–$220,000+ | Full custom construction, CBS walls, impact-rated windows, roof, permitting, impact & sewer tap fees |
Zoning: What Palm Beach County Actually Allows
Rules differ sharply depending on whether your property sits in unincorporated Palm Beach County or inside one of the county's cities and towns — each municipality (West Palm Beach, Boca Raton, Delray Beach, Jupiter, and others) sets its own accessory dwelling ordinance.
In unincorporated Palm Beach County, lots over one acre can build an accessory dwelling with up to 1,000 square feet of air-conditioned living space. Lots under one acre are capped at 800 square feet of AC space, plus up to 500 additional square feet of covered, non-conditioned area such as a carport, porch, or porte-cochère. The ADU must meet the same setback requirements as the main house and typically sits in the side or rear yard.
Florida's Live Local Act preemption (F.S. §163.31771) requires every local government in the state to allow ADUs in single-family zones by December 1, 2026 — but it lets each city and county set its own size limits, setbacks, owner-occupancy rules, and design standards. That means the West Palm Beach ordinance, the Boca Raton ordinance, and the unincorporated county rule are not the same document, and a lot that qualifies in one jurisdiction may not qualify next door. We pull the specific zoning letter for your parcel before quoting — don't rely on what your neighbor was told.
Owner-Occupancy Requirement
Most Palm Beach County jurisdictions require the property owner to occupy either the main house or the ADU as their primary residence — you generally cannot rent out both units to two unrelated tenants. This is a zoning compliance issue, not a suggestion, and it's checked at permit application.
Impact Fees and Sewer Tap Fees: The Cost Nobody Mentions Upfront
This is where Palm Beach County ADU projects diverge hardest from the online calculators. A new detached ADU in unincorporated Palm Beach County triggers county impact fees — covering roads, parks, schools (if applicable), and law enforcement — that typically run $8,000–$18,000 depending on unit size and location. If the property isn't already on a sewer connection sized for a second unit, sewer tap and capacity fees add another $4,000–$12,000.
A garage conversion that reuses the existing structure and doesn't add a new address or utility meter often avoids the full impact fee schedule — which is a major reason garage conversions run less than half the cost of new detached construction in this county.
| Fee Type | Typical Range | Applies To |
|---|---|---|
| County Impact Fees | $8,000–$18,000 | New detached ADU, new address/utility meter |
| Sewer Tap / Capacity Fee | $4,000–$12,000 | Properties without existing capacity for a second unit |
| Building Permit Fees | $1,200–$3,500 | All ADU types — scales with square footage & valuation |
| Site Plan / Zoning Review | $400–$1,200 | New detached construction, some conversions |
Homeowners almost always ask about impact fees but forget to ask whether the garage they want to convert is currently required parking under their lot's zoning. In unincorporated Palm Beach County, if you convert a garage to living space, you generally have to replace that parking elsewhere on the lot — typically a paved driveway extension or carport — before the county will sign off. Skip this and the final inspection fails, even after the interior work is finished and beautiful. We verify the parking replacement requirement against your specific zoning district before we ever price the conversion.
How much does an ADU cost in Palm Beach County? A garage conversion ADU in Palm Beach County costs $45,000–$95,000. A new detached ADU costs $120,000–$220,000+, with the difference driven mainly by foundation work, utility extension, and county impact and sewer tap fees of roughly $12,000–$30,000 that apply to new construction but usually not to garage conversions.
Garage Conversion vs. Detached ADU: Which Costs Less Long-Term
Garage conversions win on upfront cost and permit timeline — typically 6–10 weeks from application to permit issuance versus 10–16 weeks for new detached construction, since the conversion doesn't require a new foundation inspection or a full site plan review in most cases. Detached ADUs win on rental flexibility and resale value, since they read as a genuinely separate structure rather than a converted garage, and in most Palm Beach County jurisdictions they don't require replacing lost parking (since no parking is being converted).
For most homeowners, the deciding factor is the garage itself: if it's a two-car garage in good structural condition with reasonable ceiling height, conversion is almost always the better dollar-per-square-foot outcome. If the goal is a standalone rental unit and the garage is needed for storage or vehicles, a detached build is worth the added cost.
ADU Rules Vary Widely Within Palm Beach County
"Palm Beach County" is not one zoning authority — it's unincorporated county land plus 39 separate municipalities, each with its own accessory dwelling ordinance. West Palm Beach's ADU rules, adopted to comply with the Live Local Act, differ from Boca Raton's, which differ again from Delray Beach's and from the unincorporated county standard described above. Lot size minimums, maximum ADU square footage, and whether short-term rental of the unit is permitted all vary by jurisdiction.
This matters most for investors and house-hackers looking at Palm Beach County property specifically for ADU rental income. A lot that qualifies for an 800-square-foot detached ADU in unincorporated county land might be limited to 600 square feet a mile away inside city limits, or might face an owner-occupancy requirement that rules out a straight rental play entirely. Some municipalities also restrict ADUs from being rented on a short-term basis (under 30 days) even when the main house is owner-occupied.
Before you budget for a specific size or configuration, confirm which jurisdiction your parcel falls under and pull that specific ordinance — not the county-wide summary that most online guides reference.
Getting an Accurate Number for Your Property
Every number above is a range because ADU cost in Palm Beach County depends on your specific parcel: lot size, existing utility capacity, whether you're in unincorporated county or a municipality, and your garage's current structural condition. A written, line-item quote requires a site visit and a zoning verification letter — not a phone estimate.
D&Co pulls the zoning determination, confirms impact fee exposure, and provides a written scope and fixed price within 48 hours of a site visit. We're a licensed Florida General Contractor (CGC1531095) and we handle the permitting directly — no subcontracted middlemen on the paperwork that determines whether your ADU is legal.