Everything homeowners ask about building an ADU in Miami — answered with 2026 data.
Yes, ADUs are allowed in By right on a lot with a single-family residence in T3-L and T3-O (not T3-R) and in T4, T5 and T6 (Miami 21 Art. 4 Table 3; Sec. 3.18, Ord. 14375). Check your transect on the Miami 21 atlas: many single-family blocks are T3-R, where ADUs remain prohibited. Unincorporated Miami-Dade County uses its own rules (County Sec. 33-22: AU, EU, RU districts). in Miami, FL. The maximum size for a detached ADU is 10% of lot area, up to 800 sq ft; the cap cannot be Waived (Art. 6 Table 13). Minimum sizes: 275 sq ft efficiency, 450 sq ft one-bedroom, 550 sq ft two-bedroom. A 5,000 sq ft lot therefore allows 500 sq ft; you need an 8,000 sq ft lot to reach 800 sq ft. Attached ADUs can be up to Inside or attached to the house: 10% of lot area, up to 500 sq ft. Miami has an ADU-friendliness score of 6/10. Check our full Miami ADU rules page for complete zoning details.
ADU construction in Miami typically costs $150,000-$320,000. The cost per square foot averages $250-$450. Garage conversions are more affordable at $80,000-$160,000, while prefab ADUs cost $130,000-$250,000. Permit fees add About $2,200-$3,500 in city building fees on a $200,000-$350,000 unit: 0.50% of construction cost (min $110), $2.80 per $1,000 up-front, solid-waste $0.22 per $100 (max $600), energy $0.11/sq ft, CO $105 (Res. R-26-0200, 4/23/2026); zoning $250 up-front; impact fees extra. to your budget. See our detailed Miami ADU cost guide.
Detached ADUs in Miami can be up to 10% of lot area, up to 800 sq ft; the cap cannot be Waived. Attached ADUs are limited to Inside or attached to the house: 10% of lot area, up to 500 sq ft. Junior ADUs (JADUs) have a cap of No junior-ADU category. Converting rooms inside the house is simply an attached ADU (max 500 sq ft) and must contain its own sleeping/living area, bathroom and a kitchen with sink, food-prep counter and refrigerator (Sec. 3.18). Maximum height is Ancillary buildings: 2 stories and 25 ft to top of slab or eave, and never taller than the house (Illustration 5.3). Second-story walls that abut a neighbor may have only clerestory windows no more than 24 in tall (Sec. 3.18). You are allowed up to 1 ADU per lot, only on lots with a single-family residence on a qualifying lot.
Rear setback: 5 ft for a detached or one-story ancillary building (Illustration 5.3, Ancillary Building Setback). A two-story ADU attached to the house follows the principal rear setback of 20 ft (Sec. 3.18). Side setback: 5 ft per side for a detached or one-story ancillary building. A two-story attached ADU follows the principal side setback: 20% of lot width in aggregate, minimum 5 ft per side (Illustration 5.3). Front setback: 20 ft from the principal frontage and 10 ft from a secondary (corner) frontage for principal and ancillary buildings alike; a detached two-story ancillary building must also sit 10 ft from the house (Sec. 3.18, Illustration 5.3). Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
1 space per ADU (Art. 4 Table 4); none required inside a TOD or Transit Corridor. If the existing house leaves no room in the second or third layer, the space may go in the front layer on 2-ft-wide parking strips, exempt from driveway-separation and pervious-paving rules (Sec. 3.18). Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
House and ADU must be under the same ownership, and the ADU may be rented only while the property has current homestead status, so in practice the owner must live on site to rent it. The unit must be used predominantly as permanent housing and is subject to registration and annual renewal under the City Code (Sec. 3.18). Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in Miami is typically Not published by the City. Florida Statute 553.792 gives the City 30 business days to review a complete residential application per cycle; plan on 3-6 months from submittal to permit including re-reviews and Miami-Dade County sign-offs. Plan check: Not published; F.S. 553.792 sets a 30-business-day clock per review cycle, and re-reviews after the second cycle cost $56 per discipline. Pre-approved plans availability: No City of Miami program. Miami-Dade County's ADU Blueprint plans are pre-approved by the County Building Department for unincorporated-area permits; City of Miami permits are reviewed by the City's own Building Department.
Average ADU rental income in Miami: 1-bedroom units rent for $2,100-$2,500/month, 2-bedroom units for $2,500-$3,000/month. Short-term rentals: Not permitted: Sec. 3.18 requires the ADU to be used predominantly as permanent housing, and it may be rented only while the property has homestead status. Expected ROI: 6-8% net annual return.
The minimum lot size for an ADU in Miami is T3 lots: 5,000 sq ft and 50 ft wide minimum (Illustration 5.3); no separate ADU lot minimum, but the 10%-of-lot cap means a 5,000 sq ft lot gets a 500 sq ft unit. Lot coverage 50% (first floor), 30% second floor in T3-L, green space 25%. This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
Garage conversions are one of the most popular and affordable ADU options. In Miami, a garage conversion typically costs $80,000-$160,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.
Tell us about your project and we'll pass it to ADU builders serving Miami. Free, no obligation — you choose who to work with. We don't have builders in every area yet; if nobody covers yours, we'll email you to say so.
🔒 Your info is secure. We share it only with contractors quoting your project. No spam, no obligation.
Just browsing? Search ADU builders near you by ZIP code.