The county promotes development of accessory dwelling units as a means of enhancing and creating opportunities for individual property owners to provide housing options for families and generate rental income.

A. Performance Standards. An ADU shall comply with the following standards:

1. Where Permitted. An accessory dwelling unit (ADU) may be allowed in all Comprehensive Plan designations, and in all zoned areas except for MH, ML, C-1, and C-2, on a lot occupied by an existing single-family dwelling.

2. Minimum Lot Size. An ADU shall not be established on any parcel smaller than 6,000 square feet.

3. Configuration. ADUs shall be permitted as an additional dwelling unit that may be either within, attached to, or detached from the primary single-family dwelling.

4. Density. In areas classified as urban and suburban in the Cowlitz County Comprehensive Plan, one attached ADU and one detached ADU may be established as an accessory to a single-family dwelling per lot. In all other Comprehensive Plan classifications, only one ADU may be established as an accessory to a single-family dwelling per lot.

5. Building Permits. ADUs require building permits to ensure compliance with applicable fire, health and safety codes.

6. Maximum Unit Size. The gross floor area (square footage), calculated from finished wall to finished wall on all levels of an existing structure, an addition, or new detached structure, converted to or constructed for the purpose of creating an ADU shall not exceed 1,200 square feet. The maximum height shall be no taller than 35 feet or two stories.

7. Minimum Unit Size. The gross floor area (square footage) of an ADU shall not be less than that allowed by state law and the requirements of the adopted building code, Chapter 16.05 CCC.

8. Setbacks. The applicable setbacks shall be the same as those prescribed for the primary residence.

9. Connectivity. Attached ADUs shall have at least one external entry.

10. Accessibility. To encourage the development of housing units for people with disabilities, the responsible official may allow reasonable deviation from the stated requirements of this section to install features that facilitate accessibility.

11. Parking. Additional on-site parking of one space is required in conjunction with the establishment of each ADU. The off-street parking requirements set forth in CCC 18.10.562 shall be maintained for the primary residence. No additional curb cuts shall be allowed to accommodate an ADU.

12. Repealed by Ord. 20-036.

13. Temporary Accessory Dwelling Units. Accessory dwelling units not intended for permanent use may be allowed in temporary medical hardship situations upon recording of a covenant stating that the dwelling will be removed once the medical hardship has ended or prior to sale of the property to a third party, whichever occurs first. [Ord. 20-036 § 1, 5-5-20; Ord. 18-093 § 1, 10-16-18.]

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