What Does an ADU Actually Cost in Central Florida in 2026?

2026 cost breakdown for a Central Florida ADU — construction, permits, impact fees, and site work with realistic ranges for all nine counties.

By Andy West Ocala, FL

The short answer for Central Florida in 2026: a detached 600–800 sq ft ADU runs roughly $180,000 to $280,000 for most homeowners. A garage conversion of comparable size runs roughly $90,000 to $150,000. An internal conversion — walling off part of the primary dwelling to create an independent unit — is cheaper still, typically $60,000 to $110,000 if the structure already has the plumbing to support a second kitchen and bath.

Those ranges are honest, and they hide a lot of detail. The detail is what determines whether a project makes financial sense. A homeowner who builds a 650 sq ft detached ADU in Polk County on a half-acre parcel with existing septic and well may come in under $165,000. The same footprint, same finishes, on a quarter-acre Orange County lot requiring a new sewer tap and a school impact fee, will land closer to $245,000 — on the same house. The site, the county, and the method of construction drive most of the variance.

This page breaks every cost line item out, shows what drives the range, and flags the costs that are most commonly underestimated. Last verified: 2026-04-21.

The five cost buckets

Every ADU cost in Central Florida falls into one of five buckets. Understanding all five is the difference between a realistic budget and one that falls apart at permit time.

Structure. The actual building — foundation, framing, exterior walls, roof, windows, doors, interior finishes, kitchen, bath, HVAC, electrical, plumbing. This is the biggest single number in any ADU budget. For a detached 600–800 sq ft unit in Central Florida in 2026, it runs $170 to $310 per square foot for stick-built construction with standard finishes. Modular and prefab construction runs $150 to $270 per square foot delivered and set — but that delivered price does not include the foundation, utility connections, or site work. Those are in the site-work bucket below.

Florida’s hurricane code adds roughly 15–20% to structural costs compared to an equivalent build in a non-coastal state. Hurricane-rated windows, roof bracing, wind-load engineering — none of that is optional. It is what it costs to build to code in Florida.

Site work. Everything outside the building footprint that makes the build possible. Clearing and grading, foundation prep, driveway extension, utility trenching, landscape restoration, and — for properties not already connected — a new septic or sewer connection and a new well or water meter. For a typical Central Florida property already on public water and sewer, site work runs $15,000 to $35,000. For a property that needs a new septic system, add $8,000 to $18,000 depending on soil conditions. For a new well, add $6,000 to $14,000.

In parts of Lake, Polk, and Marion counties, poor soil drainage or proximity to surface water can require a more complex treatment system that runs $22,000 to $35,000. Order a soil test early — this is the single most common cost that gets discovered late and blows budgets.

Soft costs. The professional services that happen before construction starts. A boundary and topographic survey, required in every Central Florida county, runs $600 to $1,200. Architectural drawings for a 600–800 sq ft detached ADU run $4,000 to $9,000 for a straightforward plan; more for custom designs or tricky site conditions. Structural engineering for Florida wind-load certification runs $1,500 to $3,500. Civil engineering (needed when the project alters drainage or utility connections) runs $2,500 to $6,000. Plan review back-and-forth with the county typically adds one or two rounds at $500 to $1,500 each.

A solid soft-cost budget for a detached ADU is $10,000 to $20,000 total. A conversion with minimal design work can come in under $5,000.

Permit and impact fees. This is the bucket that varies most by county and the one most commonly left out of early estimates. Two different things: the permit fee is what the county charges to review your plans and inspect construction. The impact fee is a separate charge to fund roads, schools, parks, and other infrastructure the new unit will use.

Permit fees for a 600–800 sq ft detached ADU in Central Florida run $800 to $2,200. Impact fees are where the real variance is — from around $2,000 in Marion County to over $21,000 in Osceola County just for the transportation fee. The county-by-county breakdown is in the section below.

Financing carry. The interest that builds up during construction on any money you borrow to build. A $200,000 construction loan drawn down over six months at 2026 Central Florida rates (around 8.0–8.75%) carries roughly $6,000 to $9,000 in interest before it converts to a regular mortgage. Homeowners paying cash skip this bucket. Homeowners using a HELOC start paying interest on drawn balances from day one. This cost is routinely left out of rough estimates, which is why a project “budgeted” at $200,000 often closes at $215,000.

County-by-county permit and impact fee variance

These are the 2026 totals for combined permit plus impact fees for a typical 600–800 sq ft detached ADU in each of the nine counties. You pay these to the county before construction begins — they are separate from everything else above. Impact fee schedules are updated on different cycles in different counties; verify the current numbers directly with the county before locking any budget. For a side-by-side comparison table across all nine counties, see the impact fee comparison page.

Orange County has the highest combined fees in Central Florida. A 600 sq ft detached ADU typically draws $1,800 to $3,500 in permit and admin fees, plus a school impact fee in the high four figures and additional road and parks fees — combined totals routinely exceed $8,000, often higher for units above 750 sq ft. Budget at the high end.

Osceola County runs $2,500 to $4,500 for the permit and county impact fee portion. The transportation impact fee increased approximately 117% in 2025 and now runs around $21,710 alone for a new dwelling unit. Combined totals including school and fire fees can exceed $25,000. See the full impact fee comparison.

Seminole County runs $2,000 to $3,800 for the permit and county portion. School impact fees push combined totals to roughly $5,500 to $8,000 for a 600 sq ft unit.

Volusia County runs $1,900 to $3,400, with combined school and road fees bringing totals to roughly $5,000 to $7,500 for most ADUs. Coastal properties east of I-95 may pay more.

Brevard County runs $1,700 to $3,200 with combined totals typically in the $4,500 to $7,000 range. Brevard has kept ADU-related fees lower than most I-4 corridor counties.

Lake County runs $1,600 to $3,000 for the permit and county portion. Combined totals with the school fee land around $4,500 to $6,500. Note that Lake County currently prohibits independent kitchens in guest houses — a true ADU with a full kitchen is not permitted under the current code as written. Confirm the current rule before budgeting.

Polk County runs $1,500 to $2,800 and is among the lowest-cost counties in the region. Combined totals typically run $3,500 to $5,500 for a 600 sq ft ADU. Rural and semi-rural Polk properties often see the lowest total cost of entry in Central Florida.

Marion County runs $1,400 to $2,800. Combined totals land around $3,500 to $5,500 for a typical detached unit. Verify the current schedule directly with Marion County Building Safety — it updates annually.

Sumter County runs $1,800 to $3,200 for its Family Accessory Cottage program. Combined with school and road impact fees, totals fall in the $4,500 to $7,000 range. The school impact fee applies even though the unit is restricted to family occupancy — that is how Florida impact fees work. They are charged based on the new dwelling unit, not based on who lives in it.

The short version: Orange, Seminole, and Osceola (the I-4 corridor) carry the highest combined fees. Lake, Polk, Volusia, and Brevard are 30–50% lower. Marion and Sumter are lower still. If you have flexibility on location, county selection can save you $5,000 to $20,000 in fees alone.

Three real-number examples

The way the five buckets add up is easier to see with specific projects. All three use realistic 2026 numbers. None includes the purchase price of the land — all three assume you already own the property.

Example 1: Stick-built detached ADU, Polk County, 650 sq ft. The homeowner owns a half-acre parcel on existing well and septic with capacity for a second unit.

  • Structure at $210/sq ft: $136,500
  • Site work (driveway extension, utility trenching, landscaping): $18,000
  • Soft costs (survey, architectural drawings, structural engineering): $12,000
  • Permit plus impact fees (low end of Polk’s range): $4,500
  • Financing carry on a $150,000 construction loan over 6 months at 8.25%: $6,200
  • Contingency (10% of structure and site): $15,450
  • Total: $192,650

This is the low end of realistic for a stick-built detached unit in Central Florida.

Example 2: Modular detached ADU, Orange County, 750 sq ft. The homeowner owns a quarter-acre parcel in unincorporated Orange County on city water and sewer.

  • Modular unit delivered and set at $220/sq ft: $165,000
  • Site work (foundation, new sewer tap, water meter upgrade, driveway widening): $32,000
  • Soft costs: $14,000
  • Permit plus impact fees (school, road, parks for a 750 sq ft two-bedroom): $10,200
  • Financing carry on a $210,000 draw over 5 months at 8.5%: $7,400
  • Contingency (12%): $23,640
  • Total: $252,240

This represents a typical mid-range detached ADU cost inside Orange County in 2026.

Example 3: Internal conversion, Seminole County, 600 sq ft. The homeowner converts an attached garage and adjoining room into a one-bedroom independent unit.

  • Framing, drywall, kitchen, bath, HVAC extension, electrical, and finishes at $160/sq ft: $96,000
  • Site work (new parking space and walkway): $6,500
  • Soft costs (no new survey needed; architectural drawings, engineering, permit support): $5,500
  • Permit plus impact fees (conversions typically pay lower impact fees): $4,800
  • Financing carry on a $90,000 HELOC draw over 4 months at 8.0%: $2,400
  • Contingency (10%): $10,250
  • Total: $125,450

Internal conversions are the cheapest path to a legal independent unit in Central Florida, by a wide margin, when the primary structure already has the plumbing and footprint to support it.

What homeowners most often underestimate

Impact fees. The most underestimated cost in Central Florida ADU planning. Homeowners frequently confuse the permit fee (usually $800–$2,200) with the total amount due at permit pickup, which can be five times larger once impact fees are added. The impact fee schedule is a separate document from the permit fee schedule. Both need to be in your budget.

Utility tap and meter fees. Most Central Florida water and sewer utilities charge a separate fee when you add a new service connection — separate from the permit and impact fees above. These can run $3,000 to $8,000 per service. A new ADU with its own water meter and sewer connection can add $6,000 to $15,000 before a single board is nailed. Call the utility provider early — some jurisdictions require a separate connection for any independent dwelling unit, which rules out sharing the main meter.

Septic system upgrades. If your property is on septic, the Florida Department of Health requires proof that your existing system has capacity for the added dwelling. In most cases this means a new system or a significant expansion. A conventional new system runs $8,000 to $18,000. An engineered system (required on properties with poor drainage or near protected waterways) runs $22,000 to $35,000. The DOH approval can also take 6 to 10 weeks on its own — independent of the county building permit timeline.

Landscape and driveway restoration. Construction tears up your yard. A realistic budget includes $4,000 to $9,000 for final grading, driveway repair, sod, landscaping, and irrigation repair. Contractors routinely omit this from their quote and add it as a change order at the end.

Change orders. About 10–15% of ADU projects hit an unexpected problem mid-construction — unexpected soil conditions, a missed code requirement caught at a framing inspection, an owner-requested change. A 10% contingency in your budget is the minimum, not the target.

Certificate of occupancy delays. The final inspection and occupancy permit requires clearing a punch list that may include items outside the builder’s direct control. A delay means your construction loan keeps accruing interest at the higher construction rate instead of converting to a regular mortgage. Two weeks of delay on a $200,000 construction loan at 8.5% adds roughly $775 in extra interest. Six weeks adds $2,300.

How to build a reliable budget for your specific property

The ranges above are accurate for a typical homeowner, but your ADU’s cost depends on details the ranges can’t capture. Five steps will get you to a solid number in about 30 days.

Step 1: Pull the current impact fee schedule for your county. Every county publishes this on its website, usually as a PDF from the Building Department or Impact Fee page. Find the category for “accessory dwelling unit,” “secondary dwelling unit,” or the equivalent. If the schedule doesn’t use those terms, read the footnotes — most counties define how ADUs are assessed relative to the standard single-family rate.

Step 2: If your property is on septic, order a soil drainage test. If it’s on public water and sewer, call the utility and ask about capacity for a second unit. Both steps cost under $500 and protect you from finding out at permit time that you need a $25,000 system upgrade.

Step 3: Get itemized quotes from two or three builders. Not a lump-sum “per square foot” quote — an itemized breakdown separating structure, site work, and soft costs. Builders who won’t itemize will surprise you at the end.

Step 4: Call the county planning department and ask for a fee estimate in writing. Staff won’t give you an exact number over the phone — that happens at permit application — but they will confirm which impact fee categories apply to your project. Get the answer by email.

Step 5: Get a rate quote from one lender. Even if you’re not sure you’ll borrow, knowing the current construction loan rate puts a real number on the financing carry bucket in your budget.

Homeowners who work through these five steps end up within about 10% of actual cost. Homeowners who skip them routinely miss by 20% or more.

Primary sources

For the full county-by-county impact fee comparison, see the impact fees page. For financing options at current 2026 rates, see the financing page.