Unincorporated only: This page covers the unincorporated area of Hillsborough County — parcels outside any city, regulated by the County Planning / Land Use Services Department. If your address is inside a city (Tampa), use that city's ADU page instead.
These rules cover UNINCORPORATED Hillsborough County - Brandon, Riverview, Valrico, Lutz, Carrollwood, Town 'n' Country, Citrus Park, Apollo Beach, Ruskin and similar communities - not the cities of Tampa, Temple Terrace or Plant City, which have their own codes. Land Development Code Sec. 6.11.02 allows one accessory dwelling, attached or detached, with up to 900 sq ft of living space on a lot of at least 7,000 sq ft that holds an owner-occupied single-family home; it is a Conditional Use checked during building-permit review, with no zoning hearing (Sec. 6.11.01.A, Table 2.02.02). The limits that catch people are fixed by the code and cannot be varied: the main house must be owner-occupied, one unit per lot, and a detached unit in a front yard must sit at twice the district front setback (or 50 ft, whichever is less). Expect a building permit at $1.00 per sq ft under roof plus roughly $13,800 in mobility, school, park and fire impact fees for a 900 sq ft unit in the urban zone ($17,200 rural). Florida has no statewide ADU mandate - 2025's HB 943 and 2026's SB 48 both died - so the county text, unchanged since Ordinance 20-17 (October 2020), fully governs.
Zoning & Size Requirements [1][2][3][4][5][6][7][8]
Yes — unincorporated Hillsborough County allows ADUs. A detached ADU can typically be up to 900 sq ft under Florida state law and the County's zoning code.
See what this means for your lot — ask Hillsborough County ADU builders for a quote →
| Where ADUs Are Allowed | Conditional Use (no hearing) in agricultural AM, A, AR, AS-0.4, AS-1 and ASC-1 and single-family RSC-2, RSC-3, RSC-4 and RSC-6; in RSC-9 only on a lot of 7,000 sq ft or more (Table 2.02.02 note 14); in RDC-6, RMC-6, RMC-9, RMC-12, RMC-16 and SPI-UC-1/UC-3 only where the parcel holds an owner-occupied single-family detached home (note 15). Not listed for RSC-10, RDC-12, RMC-20, AI or commercial districts; Planned Developments follow their PD conditions |
| Max Size (Detached) | 900 sq ft of living space, measured to the outside faces of the exterior walls; unconditioned garages and attics used only for parking or storage, and covered patios, do not count (LDC 6.11.02.C). A variance up to 1,200 sq ft or 25% of the main home's living space, whichever is less, can be requested only on a lot of 14,520 sq ft or more |
| Max Size (Attached) | Same 900 sq ft living-space cap - the unit may be attached to the house or detached (6.11.02.C-D); an attached unit must meet the district front setback, which cannot be varied for applications filed on or after January 1, 2021 (6.11.02.F.1) |
| Max Size (JADU) | No junior-ADU category in the county code or in Florida law; an interior unit is simply an attached accessory dwelling under the same 900 sq ft cap, and it must have its own kitchen, bathroom and sleeping area (Part 12.01.00 definition) |
| Max Height | No ADU-specific cap - the district height limit applies: 35 ft in the RSC, RDC and RMC-6/9/12 districts, 50 ft in the agricultural districts (LDC 6.01.01). A unit above a detached garage or other accessory structure is allowed only where the main house has two or more stories (6.11.02.G) |
| Max Units | One accessory dwelling per lot, on the same lot as the principal dwelling - not variable (6.11.02.H). Any other detached structure, or space that cannot be reached from inside the house, may not be used for living or sleeping, including guest visits (6.11.02.I) |
Setback & Parking Requirements [1][2][3][4][5][6][7][8]
Unincorporated Hillsborough County requires a rear setback of about 25 ft for a detached ADU, and parking requirements vary by unit size or location. Owner-occupancy is required.
| Rear Setback | Principal-building rear setback of the district: 25 ft in RSC-2, RSC-3, RSC-4 and RSC-6; 20 ft in RSC-9, RDC and RMC; 50 ft in agricultural districts (LDC 6.01.01, 6.11.02.E). A unit above a detached garage on a two-story-house lot may use the accessory-structure setback instead - not closer than 3 ft to the rear line (6.11.02.G, 6.11.04.C) |
| Side Setback | Principal-building side setback: 7.5 ft in RSC-3, RSC-4, RSC-6 and RDC-6; 10 ft in RSC-2 and RMC; 5 ft in RSC-9 and RDC-12; 25 ft in AM, A, AR and AS-0.4 and 15 ft in AS-1/ASC-1 (LDC 6.01.01). The 3 ft accessory-structure side setback is available only for a unit above a detached garage where the house has 2+ stories (6.11.02.G, 6.11.04.C) |
| Front Setback | District front setback: 25 ft in RSC-2 through RSC-6, RDC-6 and RMC; 20 ft in RSC-9 and RDC-12; 50 ft agricultural (6.01.01). A detached unit in a yard that functions as a front yard must sit at twice the required front setback or 50 ft, whichever is less - not variable for applications filed on or after January 1, 2021; on a lot whose house has a legal non-conforming front setback, the unit may be no closer to the street than the house (6.11.02.F) |
| Parking Required | Sec. 6.11.02 sets no ADU parking requirement and the Sec. 6.05.02 parking schedule has no accessory-dwelling line (a conventional single-family home needs 2.0 spaces per dwelling unit) - ask Development Services whether an added space is required before you site the unit |
| Owner Occupancy | Required and not variable: the lot must be occupied by a principal detached single-family dwelling that is owner-occupied, and the code says 'these requirements shall not be varied' (LDC 6.11.02.B; the Part 12.01.00 definition and Table 2.02.02 note 15 repeat it) |
| Min Lot Size | 7,000 sq ft, on a conforming or legal non-conforming residential lot developed with a detached single-family home, unless a Planned Development expressly permits less (6.11.02.A); 14,520 sq ft or more to request the variance above 900 sq ft (6.11.02.C) |
Permit Process & Fees [9][10][11][12][13][14][15][16][17][18]
An ADU in unincorporated Hillsborough County is approved administratively — no public hearing. Typical timeline: the state building-permit clock - Florida law requires a decision within 30 business days of a complete application for a residential unit under 7,500 sq ft (F.S. 553.792); the county publishes no ADU-specific review time. Fees range from $1.00 per sq ft under roof for R-3 residential (minimum $380, includes building, mechanical, electrical and plumbing; schedule effective October 5, 2024) plus about $13,800 in mobility, school, park and fire impact fees for a 900 sq ft unit in the urban zone ($17,200 in the rural zone).
| Approval Process | Conditional Use ('C' in Table 2.02.02): compliance with Sec. 6.11.02 is checked during building-permit review with no separate zoning application or public hearing (Sec. 6.11.01.A). Apply on the HillsGovHub portal as new residential construction - the county's single-family new-construction checklist expressly covers accessory dwelling units. Only a size variance (lots of 14,520+ sq ft) goes through the variance process |
| Review Timeline | the state building-permit clock - Florida law requires a decision within 30 business days of a complete application for a residential unit under 7,500 sq ft (F.S. 553.792); the county publishes no ADU-specific review time |
| Permit Fees | $1.00 per sq ft under roof for R-3 residential (minimum $380, includes building, mechanical, electrical and plumbing; schedule effective October 5, 2024) plus about $13,800 in mobility, school, park and fire impact fees for a 900 sq ft unit in the urban zone ($17,200 in the rural zone) |
| Impact Fees | No ADU exemption - Code of Ordinances Sec. 40-55 exempts only accessory buildings that add no impact, and fees are assessed per dwelling unit. Schedules in force since October 1, 2022: mobility $8,178 urban / $11,633 rural for a unit under 1,500 sq ft; school $1,645 under 900 sq ft or $3,891 at 900-1,299 sq ft; park $1,368 at 750-999 sq ft; fire $335. Water and sewer impact fees (RS25-111, from March 23, 2026) apply only if the unit gets its own county meter |
| Plan Check | Florida Building Code plans digitally signed and sealed by a Florida architect or engineer, plus a scaled site plan showing every setback, easement and tree; the plan-review half of the permit fee is due before review starts. Tree removal for the unit needs a Land Alteration permit filed in the same HillsGovHub application (Development Services FAQ) |
| Pre-Approved Plans | None - the county has no pre-approved ADU plan program (checked September 2026) |
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Construction Costs [19][20][21][22]
Building an ADU in unincorporated Hillsborough County typically costs $100,000-$250,000 ($170-$350 per sq ft); a garage conversion runs $60,000-$140,000.
See what this means for your lot — ask Hillsborough County ADU builders for a quote →
Construction costs in unincorporated Hillsborough County track the surrounding metro market. Rural parcels can cost more because of septic, well, access and fire-hazard requirements, so treat these as planning ranges and get local bids.
| Average Build Cost | $100,000-$250,000 |
| Cost per Sq Ft | $170-$350 |
| Garage Conversion | $60,000-$140,000 |
| Prefab ADU (Installed) | $90,000-$200,000 |
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Rental Income Potential [23][24]
| Avg Rent (1 Bedroom) | $1,500-$2,300/mo |
| Avg Rent (2 Bedroom) | $1,750-$2,700/mo |
| Short-Term Rental | Sec. 6.11.02 is silent on rental term, but the main house must stay owner-occupied for the unit to remain lawful. |
| Est. Annual ROI | 5-8% annual return (market estimate) |
Recent Law Changes
What's Changed Recently
- September 2026 check: LDC Supplement 58 (codified through Ordinance 26-8 of January 15, 2026; posted online August 20, 2026) shows Sec. 6.11.02 unchanged since Ordinance 20-17 (adopted September 24, 2020, effective October 2, 2020), which added the front-yard placement rule, allowed legal non-conforming lots and opened RSC-9 lots of 7,000 sq ft or more to accessory dwellings
- No ADU item in the 2025-2026 amendment cycles: the county's recently adopted list (LDC 25-0399 through 26-0189; Table 2.02.02 last amended by Ordinance 25-58, effective December 11, 2025, for certified recovery residences) touches nothing in Sec. 6.11.02; 2026 Round 1 had no proposals and the Round 2 first hearing is set for October 8, 2026
- Fees: the building-permit fee schedule effective October 5, 2024 charges $1.00 per sq ft under roof for R-3 residential (minimum $380); the mobility, school, park and fire impact schedules have been unchanged since October 1, 2022; county water and wastewater connection impact fees rose March 23, 2026 (RS25-111) and step up each March through 2029; on September 2, 2026 the Board directed staff to draft an annual impact and mobility fee review policy
- Florida 2026 session: SB 48, which would have required every county and city to allow ADUs in single-family zones by December 1, 2026 and barred owner-occupancy requirements, passed the Senate but died in House messages on March 13, 2026; the companion that became law (HB 1389, Ch. 2026-179) contains no ADU provision. F.S. 163.31771 still says a local government 'may' allow ADUs and was last amended in 2020. 2025's HB 943 was laid on the table April 29, 2025
- Accuracy note: builder and prefab marketing pages still claim a 'Florida SB 943' ADU mandate 'effective July 1, 2025' with a 750 sq ft state cap - no such law passed; the county's 900 sq ft cap and owner-occupancy rule remain in force
Tips for Building an ADU in Unincorporated Hillsborough County
- Check whether your address is unincorporated before reading further: Tampa, Temple Terrace and Plant City each have their own ADU rules (Tampa allows ADUs only in designated areas). Brandon, Riverview, Valrico, Lutz, Carrollwood, Town 'n' Country, Citrus Park, Westchase, Apollo Beach, Ruskin, Sun City Center, Gibsonton, Seffner, Thonotosassa and Lithia are county
- The owner-occupancy rule cannot be varied (LDC 6.11.02.B) - the unit works for family or rental income only while you live in the main house, and Florida's 2026 attempt to override such rules (SB 48) died
- Measure the 900 sq ft to the outside faces of the exterior walls and exclude only unconditioned garage/attic space used for parking or storage and covered patios - a plan that reads 900 sq ft inside usually exceeds the cap outside
- School impact fee band: a unit with less than 900 sq ft of living area is assessed $1,645; at 900-1,299 sq ft it is $3,891. Building to 899 sq ft rather than the full 900 saves $2,246 - ask impactfees@hcfl.gov how they measure living area before you finalize plans
- Impact-fee worked example for a 900 sq ft detached unit, urban mobility zone: mobility $8,178 + school $3,891 + park $1,368 + fire $335 = $13,772, before the building permit (about $900 at $1.00 per sq ft). The rural zone total is $17,227. A separate county water meter adds water and wastewater impact fees (from $2,037.50 + $3,268.75 Northwest to $3,449 + $4,884.75 South-Central per unit in 2026)
- Lot of 14,520 sq ft (a third of an acre) or more? You may request a variance to 1,200 sq ft or 25% of the main home's living space, whichever is less; smaller lots have no path above 900 sq ft
- A detached unit in front of the house must sit back twice the district front setback (50 ft in a 25 ft RSC district) or 50 ft, whichever is less, and that rule cannot be varied - most lots will put the unit behind or beside the house
- Cost basis: the four cost figures are 2026 Tampa-area and Florida industry guides (detached 600-950 sq ft units $90,000-$250,000; $170-$350 per sq ft site-built; garage conversions $60,000-$140,000; modular $90,000-$200,000 all-in) - not county data. Rent basis: HUD FY2027 Small Area Fair Market Rents for Brandon, Riverview, Lutz, Carrollwood, Valrico, Town 'n' Country and Citrus Park ZIP codes (1BR $1,530-$2,310, 2BR $1,780-$2,690)
- Ignore posts citing 'SB 943' or a Florida 750 sq ft state rule - the mandate never passed; the county code and this page's sources are the current rules
- Cost basis (2026-09-20 re-verification): short term allowed: Sec. 6.11.02 is silent on rental term, but the main house must stay owner-occupied for the unit to remain lawful. Stays under 30 days need a Florida DBPR vacation-rental license and are subject to state and county tourist taxes - confirm current county code-enforcement rules before listing
ADU Builders in Hillsborough County
Looking for an ADU builder in Hillsborough County? ADU projects need a contractor experienced with local zoning, the permit process, and utility connections — not every general contractor has built one. We match Hillsborough County homeowners with experienced local ADU contractors who provide free, no-obligation quotes. Getting at least three bids typically saves 20-40% on the same scope.
Cities Within Hillsborough County
If your property is inside one of these incorporated cities, follow that city's ADU code — not the County rules above:
Sources & References
All data on this page is sourced from official government records and verified market data. View our full methodology.
- Hillsborough County LDC Sec. 6.11.02 - Accessory Dwelling Standards (Supp. 58, codified through Ord. 26-8) Planning Department — Accessed 2026-09-20
- Hillsborough County LDC Sec. 2.02.02 - Allowable Uses in Zoning Districts (Accessory Dwellings row, notes 14 and 15) Planning Department — Accessed 2026-09-20
- Hillsborough County LDC Sec. 6.01.01 - Schedule of District Area, Height, Bulk and Placement Regulations Planning Department — Accessed 2026-09-20
- Hillsborough County LDC Sec. 6.11.04 - Accessory Structures (3 ft side/rear setback used for units above a garage) Planning Department — Accessed 2026-09-20
- Hillsborough County LDC Sec. 6.05.02 - Parking and Loading Standards (no accessory-dwelling line) Planning Department — Accessed 2026-09-20
- Hillsborough County LDC Part 12.01.00 - Definitions ('Accessory Dwelling') Planning Department — Accessed 2026-09-20
- LDC Text Amendment 19-1055, Accessory Dwellings - intent statement and text adopted by Ord. 20-17 (Hillsborough County BOCC Legistar) Planning Department — Accessed 2026-09-20
- Land Development Code Amendments - Hillsborough County (2026 Round 1: none proposed; recently adopted list) Planning Department — Accessed 2026-09-20
- Hillsborough County LDC Sec. 6.11.01 - Generally (conditional-use standards checked during development review) Planning Department — Accessed 2026-09-20
- Residential Single-Family New Construction Requirements (covers accessory dwelling units) - HillsGovHub, Hillsborough County Planning Department — Accessed 2026-09-20
- Building Permit Fee Schedule effective October 5, 2024 - Hillsborough County Development Services Planning Department — Accessed 2026-09-20
- Estimated Residential Impact/Mobility Fee Assessment by Zone per Dwelling Unit (effective October 1, 2022) - Hillsborough County Planning Department — Accessed 2026-09-20
- Mobility Fees - Hillsborough County (schedule of rates effective October 1, 2022) Planning Department — Accessed 2026-09-20
- Impact Fees - Hillsborough County (school, park, fire schedules; RS25-111 utility impact fees) Planning Department — Accessed 2026-09-20
- Hillsborough County Code of Ordinances Sec. 40-55 - Impact fee exemptions and existing uses Government Data — Accessed 2026-09-20
- Resolution RS25-111 - Water and wastewater impact fee rates effective March 23, 2026 - Hillsborough County Government Data — Accessed 2026-09-20
- Development Services FAQs - Hillsborough County (tree-removal permit for a detached mother-in-law suite) Planning Department — Accessed 2026-09-20
- Fla. Stat. 553.792 - Building permit application to local government (30-business-day decision for residential units under 7,500 sq ft) Government Data — Accessed 2026-09-20
- ADU Cost in Tampa: 2026 Guide - OneOak Capital industry — Accessed 2026-09-20
- ADU Laws and Regulations in Tampa, Florida - Mesocore industry — Accessed 2026-09-20
- Cost to Build an ADU in Florida (2026) - ADU Florida Info industry — Accessed 2026-09-20
- What Does an ADU Actually Cost in Central Florida in 2026? - Central Florida ADU industry — Accessed 2026-09-20
- HUD FY2027 Small Area Fair Market Rents (Tampa-St. Petersburg-Clearwater MSA ZIP codes) Government Data — Accessed 2026-09-20
- HUD Fair Market Rents - dataset page Government Data — Accessed 2026-09-20
- Fla. Stat. 163.31771 - Accessory dwelling units (2026 Florida Statutes; permissive, last amended 2020) Government Data — Accessed 2026-09-20
- SB 48 (2026) Housing - bill history, died in House messages March 13, 2026 - Florida Senate Government Data — Accessed 2026-09-20
- Florida Senate - CS/CS/SB 48 (2026) bill analysis, Rules Committee, January 27, 2026 Government Data — Accessed 2026-09-20
- CS/CS/HB 1389 (2026) Affordable Housing, enrolled text (Ch. 2026-179; no ADU provision) - Florida Senate Government Data — Accessed 2026-09-19
- HB 943 (2025) Real Property and Land Use and Development - laid on the table April 29, 2025 - Florida Senate Government Data — Accessed 2026-09-20
Frequently Asked Questions
What are the ADU rules in unincorporated Hillsborough County?
In unincorporated Hillsborough County, ADUs are regulated by the County (not a city) and follow Florida state ADU law. A detached ADU can be up to 900 sq ft of living space, measured to the outside faces of the exterior walls; unconditioned garages and attics used only for parking or storage, and covered patios, do not count, attached ADUs up to Same 900 sq ft living-space cap - the unit may be attached to the house or detached. Rear setbacks are Principal-building rear setback of the district: 25 ft in RSC-2, RSC-3, RSC-4 and RSC-6; 20 ft in RSC-9, RDC and RMC; 50 ft in agricultural districts, and qualifying ADU applications are approved administratively, with no public hearing.
How much does an ADU permit cost in Hillsborough County?
In unincorporated Hillsborough County, building and plan-check fees scale with the size and valuation of the ADU, so there is no single flat fee — request the current fee schedule from the County. No ADU exemption - Code of Ordinances Sec. 40-55 exempts only accessory buildings that add no impact, and fees are assessed per dwelling unit. Schedules in force since October 1, 2022: mobility $8,178 urban / $11,633 rural for a unit under 1,500 sq ft; school $1,645 under 900 sq ft or $3,891 at 900-1,299 sq ft; park $1,368 at 750-999 sq ft; fire $335. Water and sewer impact fees (RS25-111, from March 23, 2026) apply only if the unit gets its own county meter. Total construction typically runs $100,000-$250,000; a garage conversion is cheaper at $60,000-$140,000.
Do I need owner-occupancy for an ADU in Hillsborough County?
Required and not variable: the lot must be occupied by a principal detached single-family dwelling that is owner-occupied, and the code says 'these requirements shall not be varied' (LDC 6.11.02.B; the Part 12.01.00 definition and Table 2.02.02 note 15 repeat it).
Is my property in unincorporated Hillsborough County or inside a city?
This matters a lot: if your parcel is inside an incorporated city (Tampa), that city's ADU code applies instead of the County's. Only unincorporated parcels follow the County rules on this page. Confirm your jurisdiction with the County before designing.
How many ADUs can I build in unincorporated Hillsborough County?
One accessory dwelling per lot, on the same lot as the principal dwelling - not variable (6.11.02.H). Any other detached structure, or space that cannot be reached from inside the house, may not be used for living or sleeping, including guest visits (6.11.02.I)
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