Accessory Structures in Grant County, WA (2026)
5 rules for unincorporated Grant County, Washington.
Verified from official government sources
ADU Rules
In unincorporated Grant County, a second dwelling is allowed as an accessory to an existing single-family home, but the count and configuration differ by area. Urban growth areas allow two ADUs; the rest of unincorporated Grant County allows only one under Unified Development Code Section 23.08.020(c).
Accessory Dwelling Unit Rules, Grant County
Some RestrictionsGrant County Unified Development Code § 23.08.020(c)(1)
(c)Accessory Dwelling Unit (ADU). Accessory dwelling units are intended to increase the supply of affordable and independent housing for a variety of households. ... (1)Accessory Dwelling Unit (ADU): A residential dwelling unit located on the same lot as a single-family dwelling unit, either within the same building as the single-family dwelling unit, attached to the single-family dwelling unit...
ADU Rental Restrictions
In unincorporated Grant County, an accessory dwelling unit must be occupied as a permanent residence and cannot be used, rented, or leased as a transient short-term rental of under 30 consecutive days, under Unified Development Code Section 23.08.020(c)(1)(C).
ADU Short-Term Rental Ban, Grant County
Significant RestrictionsGrant County Unified Development Code § 23.08.020(c)(1)(C)
(C)All Accessory Dwelling Units shall be occupied as permanent residences and may not be used, rented, or leased as transient short-term rentals (less than thirty (30) consecutive days).
Shed & Carport Rules
In unincorporated Grant County, storage sheds, workshops, garages and barns are listed as permitted residential accessory uses in every zoning district under GCC UDO Section 23.08.020(n)(4). Section 23.08.020(a)(1) also lets an accessory structure up to 1,500 square feet go up before the primary home is built, as long as it is not used for residential occupancy, business or industrial use.
Grant County Accessory Building and Shed Rules
Some RestrictionsGrant County Unified Development Code § 23.08.020(a), (n)
(a)Accessory uses are customarily incidental and subordinate to the principal use of a structure or site. ... Accessory structures are permitted under the following provisions:(1)Accessory uses/structures not exceeding one thousand five hundred (1,500) square feet shall be permitted prior to the construction of a primary use. These structures are not intended for residential occupancy, business...
Garage Conversions
In unincorporated Grant County, converting a detached garage into an accessory dwelling unit is allowed and must meet all standard ADU requirements, but a garage that is already nonconforming on setbacks or lot coverage keeps that nonconformity, per Unified Development Code Section 23.08.020(c)(9).
Converting a Garage to an ADU, Grant County
Some RestrictionsGrant County Unified Development Code § 23.08.020(c)(9)
(9)Conversions: The conversion of existing structures, such as detached garages, into accessory dwelling units shall comply with all ADU requirements, except that non-conforming structures regarding setbacks and/or lot coverage are allowed to be converted to ADUs and retain their non-conformity.
Tiny Homes
In unincorporated Grant County, tiny homes are expressly allowed as accessory dwelling units alongside manufactured homes and Park Model RVs, provided the structure meets all applicable building code provisions, under Unified Development Code Section 23.08.020(c)(7).
Tiny Homes as ADUs, Grant County
Few RestrictionsGrant County Unified Development Code § 23.08.020(c)(7)
(7)Construction: Structures shall be subject to all applicable building and constructions provisions of the GCC. Manufactured Homes, Tiny Homes, Park Model RVs, and other Factory-Assembled Structures are allowed to be used as accessory dwelling units.
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