St. Tammany Parish, LA Accessory Structures: Garage Conversions (2026)

The Unified Development Code defines 'Apartment, Garage' at Sec. 100-5 as a building under 1,000 square feet of habitable space that stores automobiles while its second story is used for residential purposes, and Sec. 600-6.2(2) sets the standards that govern building or converting one on a residential lot in unincorporated St. Tammany Parish. The base cap is 1,000 square feet of habitable floor space. Owners of larger parcels get more room: on a lot over 1 acre, a guest house can scale up to 7.5 percent of the total lot area, capped at 2,500 square feet of habitable space, whichever is smaller.

Placement is restricted along with size. Every garage apartment or guest house must meet the minimum primary building setbacks that apply to the underlying zoning district, and it has to sit behind the main structure on the lot rather than beside or in front of it. Corner lots and through-lots get an added rule: where the accessory structure would otherwise face a second street, it still has to meet that street's front-yard setback, so a garage apartment cannot crowd a side street just because it is technically in the 'rear' of the property relative to the primary address.

Because these are accessory-use standards under Chapter 600, a garage apartment or conversion still needs the parish's standard building permit and site plan approval before construction, in addition to complying with the size and placement limits in Sec. 600-6.2(2).