Current St. Petersburg ADU rules must be read from the current Use Permissions Matrix together with LDR Section 16.50.010. The current Use Permissions Matrix lists Accessory, Dwelling Unit as P (Permitted) in the combined NT-1 + NT-2 Neighborhood Traditional Single-family column. Therefore, when the live city zoning layer authoritatively resolves a parcel as NT-2, the zoning-use permission condition for an ADU is satisfied, subject to the development standards below. unverified
Establishment. Not more than one ADU is permitted for each single-family dwelling in districts where the Matrix allows it. The principal building must have commenced construction or a lawful principal use must already be established. An ADU may not be used as transient accommodation.
Lot requirements. Under the city handout updated for Ordinance 611-H and effective July 18, 2025, in all NT districts the lot area must be at least 4,500 square feet. In all NS districts, the lot must have at least 10,000 square feet, or an alley lot must have at least 4,500 square feet, or a corner lot must meet the district minimum lot area and width. In other zoning districts, the lot must conform to that district's minimum lot area.
Size. The gross floor area of an ADU may not exceed 800 square feet, and all areas under roof may not exceed 67 percent of the floor area of the principal dwelling unit. The more restrictive limit controls. For a detached ADU, the percentage limit applies to the combined ADU and accessory living space in the same building, subject to the enclosed-parking exclusion stated in the city rule.
Parking and access. The Use Permissions Matrix requires one parking space for an ADU with up to two bedrooms, plus 0.5 space for each additional bedroom. The ADU handout waives the otherwise-required off-street parking only when all listed conditions are met: the property is within 660 feet of a high-frequency transit route, the ADU is 600 square feet or less, it is on an alley, all required house parking is accessed from the alley, and there is no front-loading driveway. When the rear yard is adjacent to an alley, required off-street parking is placed in the rear yard.
Applying recorded floor area. The city definition of principal-dwelling floor area controls, not a real-estate listing or an appraiser living/usable-area total. A single-building, single-family appraiser record can support a preliminary calculation, clearly labeled with that assumption. Mapped alley adjacency is not verification of legal access, driveway layout, or all parking-waiver conditions.