Miami-Dade County, FL Accessory Structures: ADU Impact Fees (2026)
Key Facts
- Governing chapter
- Ch. 33E, Multimodal Mobility Impact Fee Ordinance
- Scope
- Countywide, incorporated and unincorporated (Sec. 33E-2(c))
- ADU exemption test
- No new unit, no land-use change, no added trips
- Fee due
- Before certificate of completion, TCO, or CO issues
- Nonpayment remedy
- Stop-work order plus $10 or 5% service fee
- Lien window
- 3 years from C.U. or C.O. issuance
Summary
Miami-Dade County charges its countywide mobility impact fee on every building permit application, including new accessory dwelling units. Code Section 33E-14(d)(7) exempts accessory buildings from the fee, but only when the land use is unchanged, no additional unit is created and no added vehicle trips result, a test most ADUs fail because they add a housing unit.
(7)Existing structure alterations and accessory buildings.(i)Any alteration, replacement or expansion of an existing structure or the addition of an accessory building shall be exempted provided that the land use has not changed and no additional units are created and no additional vehicle trips are generated pursuant to Section 33E-8.(ii)A parking garage that is accessory to a primary use structure shall qualify for this exemption.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 135).
Full Breakdown
Chapter 33E, the Multimodal Mobility Impact Fee Ordinance, applies countywide: Section 33E-2(c) states it 'shall be applicable to land development in the entirety of Miami-Dade County in the incorporated and unincorporated areas,' so the fee reaches all 34 municipalities as well as the Unincorporated Municipal Service Area, not just UMSA. 1. used as an ancillary residential unit' with its own kitchen, bathroom and sleeping area, so adding an ADU is development activity that triggers the fee. Section 33E-14(d)(7) offers an exemption for 'existing structure alterations and accessory buildings,' but only when the land use has not changed, no additional units are created, and no additional vehicle trips are generated under the Section 33E-8 fee schedule.
Because an ADU adds a housing unit by definition, it does not meet that test, and the mobility fee is owed like any other new unit; a garage or storage structure that adds no unit does qualify, and a parking garage accessory to a primary structure is separately confirmed eligible. The fee amount is computed under the schedule adopted per Section 33E-8 and must be paid before a certificate of completion, temporary certificate of occupancy, or certificate of occupancy is issued for the ADU, at the rate in effect on the date plans are submitted for impact fee assessment.
Violations & Fines
Section 33E-6.1(c) bars any county or municipal building department from issuing the permit until the mobility fee is paid. If the amount paid is later found insufficient or the payment instrument fails, Section 33E-6.1(d) authorizes a stop-work order until full payment is received, plus a service fee of $10.00 or 5 percent of the invalid payment under Florida Statutes Section 68.065. Section 33E-6.1(e) lets the County lien the property if the correct fee was not paid before a certificate of use or occupancy issued, filed within three years of that certificate.
Frequently Asked Questions
Does Miami-Dade charge an impact fee for building an ADU?
Can an ADU qualify for the accessory-building exemption?
Does the mobility fee apply inside cities like Hialeah or Homestead, or only in unincorporated areas?
What happens if the ADU's mobility fee is not paid?
Sources & Official References
Other rules in Miami-Dade County
Florida rules heatmap·Compare Miami-Dade County to another location·View the Florida accessory structures overview
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