Casper, WY Accessory Structures: Shed & Carport Rules (2026)

Casper Municipal Code § 17.12.121(A) allows detached garages and accessory buildings, which includes tool sheds and playhouses, on any residentially zoned or residential-use lot recorded with the Natrona County assessor's office, and § 17.12.121(C) sets the building-permit threshold at one hundred twenty square feet measured at the maximum exterior wall dimension; a smaller one-story shed or playhouse under that size still needs a fence/accessory building permit rather than a full building permit. Setbacks scale with size under subsection F: a detached garage or accessory building normally needs a five-foot minimum rear setback, cut to three feet where it abuts an alley, but a one-story accessory building under one hundred twenty square feet drops to a one-foot minimum rear setback, compared with the standard five-foot side setback that applies to larger structures in every zoning district.

Subsection D requires a residential building already on the lot, or under construction at the same time, before a detached garage or shed can go up. Subsection F.4 caps any single accessory building at one thousand five hundred square feet, or fifteen percent of the lot's total area associated with the primary residence, whichever is smaller, with a conditional use permit from the planning and zoning commission required to exceed that ceiling. Larger buildings over one hundred twenty square feet also have to match the design, exterior materials and roof pitch of the primary residence, and vertical metal siding is barred outright on anything that size or larger.