ADU rules in Saint Petersburg

The use Matrix defines an ADU as a secondary living unit 'existing either within the same structure, or on the same lot, as the primary detached single-family house' and lists ADUs as Permitted (P) in all NT, NTM, NS, NSM, NMH, NPUD, CRT, CRS, and CCT districts plus DC-2. Detached units must meet lot requirements: NT lots at least 4,500 sq ft; NS lots at least 10,000 sq ft, or 4,500 sq ft if on an alley, or corner lots meeting district minimums; and the lot's legal front and rear must be consistent with other lots on the block face. Detached ADUs in NS districts need a 10-foot side yard setback (7.5 feet on alley lots).

An attached ADU may be located to the side or rear of the principal structure (side placement requires the unit's access to be on the side or rear and not visible from the street) and must comply with district setbacks. Attached ADUs are not permitted where lots have been refaced so the legal front yard faces a different direction than the rest of the block or where refacing eliminated alley access. A front-facade garage conversion is allowed subject to garage-door removal, architectural compatibility, a 3-foot green yard strip, and on-site replacement parking.

For detached ADUs the limit applies to the combined square footage of the ADU and any accessory living space in the same building, including storage, bathrooms, and shared laundry, but excluding up to 300 sq ft of gross floor area per required enclosed parking space (maximum three spaces). The ADU must also remain subordinate to the principal use in location, square footage, and building coverage.

The ADU ordinance (§16.50.010) contains no owner-occupancy requirement, and the city's official ADU page answers 'Does the main unit need to be Owner-Occupied or Homesteaded?' with 'No, but if both units are rental, a Business Tax Certificate is required.' (A separate use, 'Accessory Dwelling Unit, Owner/Manager', exists in the Matrix for on-premises manager units at nonresidential uses; it is not the standard ADU use.)

Matrix ratio applies in all tiers. At least one required space must be unobstructed and reserved exclusively for ADU occupants. Parking is exempt only where the property is within 660 feet of a high frequency transit route, the unit is 600 sq ft or less, the unit is on an alley, all required parking for the single-family home is alley-accessed, and there is no front-loading driveway. Required spaces go in the rear yard off the alley where one exists; a primary-street driveway is allowed only with no alley or side street and at single-lane width. A paved walkway at least 2 feet wide must connect the ADU entrance to the parking.

The use Matrix lists 'Accessory, Dwelling Unit' as P (Permitted) in all NT, NTM, NS, NSM, NMH, and NPUD neighborhood districts, CRT and CRS corridor residential districts, CCT-1/CCT-2, and DC-2, subject to the §16.50.010 use-specific standards; no special exception or public hearing is required. In CCS, most DC, RC, EC, and IC districts existing ADUs are only Grandfathered, and in DC-P, IC (T/U), IT, and IS they are Nonconforming. The city processes ADUs as building permits through its ePlan system with plan review in 3 to 5 business days per the official ADU page.

§16.50.010.4.4 states an ADU 'shall not be utilized as a transient accommodation use as defined and regulated by this chapter.' The city's official ADU page explains: in residential districts the minimum rental period is 30 days, and rentals under 30 days are allowed only 3 times in any consecutive 365-day period. If both the main home and ADU are rented, a Business Tax Certificate is required. The ordinance does not override private deed restrictions or HOA declarations restricting ADUs, though the City does not enforce them.