What Can I Build on a T3-O Lot in Miami?
On a T3-O lot you can build a duplex (two units) or a single-family home, up to 2 stories and 25 feet, on a lot of at least 5,000 SF. Density is 18 units per acre, capped at two units on any lot, and buildings can cover 50% of the lot. Apartments and commercial uses are not allowed.
T3-O at a glance
| Rule | T3-O |
|---|---|
| Homes allowed | Single-family home or duplex; an ADU only with a single-family home |
| Units per lot | 2 |
| Density | 18 units/acre |
| Max height | 2 stories and 25 ft (to top of slab or eave) |
| Lot coverage | 50% first floor; no separate second-floor figure |
| FLR (floor lot ratio) | None stated (N/A) |
| Minimum lot area | 5,000 SF |
| Minimum lot width | Not covered in this guide |
| Setbacks | Not covered in this guide |
| Parking | 2 spaces per principal home |
| Commercial / office | Not allowed |
The worked example: a 5,000 SF lot
Units by the per-lot rule: 2 (one building with two dwelling units)
Ground floor: 5,000 × 50% = 2,500 SF of footprint
Upper bound: 5,000 × 50% × 2 stories = 5,000 SF of building
Units round down, because density is a maximum. In T3 the per-lot rule binds: under Miami 21, T3-O density is 18 units per acre but never more than two units on a lot. The building-area figure is a ceiling from the coverage limits; setbacks will bring it lower.
Height
T3 buildings are limited to 2 stories and 25 feet, measured to the top of the slab or eave. A flat roof gets the same two stories and 25 feet.
Lot coverage and house size
T3 has no floor area ratio. Size is set by lot coverage: 50% of the lot on the first floor. The code sets a 30% second-floor limit only for T3-R and T3-L, so T3-O has no separate second-floor figure. Coverage counts every building on the lot, including an ancillary building.
What you can build, use by use
For T3-O, Miami 21 allows these homes:
- Single-family home: by right.
- Duplex (two-family): by right.
- Apartments (multifamily): not allowed.
- Ancillary dwelling unit (ADU): allowed by right, but only on a lot with a single-family home. So a T3-O lot is either a duplex, or a house plus an ADU, not both.
Commercial, office, lodging and industrial uses are all prohibited in T3-O.
By right means allowed if the plan meets the code. Warrant means an administrative approval by City staff. Exception means a public hearing. Any use the code doesn't list for the zone is prohibited.
Parking
The code requires a minimum of 2 parking spaces per principal dwelling unit in T3, plus 1 space per ADU.
Setbacks and lot width
We haven't verified the T3 setbacks and minimum lot width against the current code yet, so we don't state them here rather than give you a number we can't trace.
Bonuses and special programs
The main affordable-housing bonus doesn't apply to T3-zoned land. Recent changes to the code also added a path for two units on some legal nonconforming undersized T3-O lots and new cottage housing rules for T3-O. Each has its own conditions.
What can kill a deal on a T3-O lot
- Flood zone. Can set a minimum floor elevation and raise build and insurance costs.
- Easements. A recorded utility or access easement can cross the spot you planned to build on.
- Recorded liens and judgments. Code liens and lawsuits against the property can follow it to the next owner.
- Open or expired permits. A past owner's unfinished permits can block new ones until they're closed out.
- Contamination nearby. A former gas station or dry cleaner next door can trigger environmental review.
- Minimum lot size. A lot under 5,000 SF is below the T3 minimum. Confirm with the City whether a smaller lot is buildable before you price it as one.
Frequently asked questions
Can I build a duplex on a T3-O lot?
Yes. Miami 21 allows a two-family residence by right in T3-O: one building with two dwelling units on each lot.
Can I build more than two units on a large T3-O lot?
No. The density is 18 units per acre, but the code caps T3-O at two units on any lot.
Can I build a duplex and an ADU?
No. An ADU is only permitted on a lot with a single-family residence. It's a duplex, or a house plus an ADU.
How tall can I build in T3-O?
2 stories and 25 feet, measured to the top of the slab or eave.
What's the minimum lot size in T3-O?
5,000 SF. Newer cottage housing rules for T3-O work differently, so confirm with the City if your lot is smaller.
Are apartments allowed in T3-O?
No. Multifamily housing is prohibited in every T3 zone. Apartments start in T4.
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Other Miami 21 zone guides
New to zone names? Read the plain-English guide to Miami 21.
General information about the Miami 21 code, not legal or zoning advice. Overlays, special plans and prior approvals can change the answer for a lot. Confirm with the City of Miami before you apply for permits.