ADU rules in Santa Fe County

Unincorporated Santa Fe County allows one ADU, detached or attached, per legal lot of record under Section 10.4 of the Sustainable Land Development Code (SLDC, Ordinance 2016-9). The Appendix B Use Matrix lists 'Accessory dwelling units' as an accessory use (A) in every base zoning district, including Agriculture/Ranching, Rural, Rural Fringe, Rural Residential, Residential Fringe, Residential Estate, Residential Community and Traditional Community, and as permitted (P) in Planned Development, so a detached casita is allowed by right wherever it is accessory to a lawful principal dwelling. Community district overlays in SLDC Chapter 9 override this baseline: Tesuque and Madrid require a conditional use permit, and Los Cerrillos allows ADUs only in its RUR-R and RES-E overlay zones.

Section 10.4 applies 'to any accessory dwelling unit located in a building whether or not attached to the principal dwelling,' and Appendix A defines Accessory Dwelling as 'an accessory detached dwelling unit or attached dwelling unit such as an accessory apartment.' The county's permit materials likewise describe ADUs 'integral or separate from the principal residence.' The same one-per-lot, size, design and shared-utility standards apply either way.

The heated area of the ADU may not exceed the lesser of 50 percent of the heated floor area of the principal residence or 1,400 square feet (SLDC § 10.4.2.2). The ADU may not exceed one story or the height of the principal dwelling, must match the principal dwelling's architectural style and exterior materials, and must share its driveway (§ 10.4.2.3). Community overlays tighten this: 600 square feet of heated interior space in the Los Cerrillos RES-E zone (§ 9.4.5.1) and 650 square feet in the Chimayo Traditional Community district (§ 9.16.4.2).

SLDC § 10.4 imposes no owner-occupancy requirement countywide; either unit may be rented with no requirement that the owner live on the property. Two community overlays are the exception: in the Tesuque and Madrid community districts an ADU needs a conditional use permit and 'at the time of application, the primary dwelling unit shall be owner-occupied' (§§ 9.5.5.1, 9.6.5.1), an at-application test rather than an ongoing covenant. Separately, renting the ADU short-term under the county's cheaper owner-occupied STR registration requires the owner's primary residence to be on the same lot; otherwise the ADU STR needs a non-owner-occupied business license (county code § 110.09(H)).

Section 10.4 sets no parking count for ADUs, but requires the ADU to be 'accessed through the same driveway as the principal residence' with no separate curb cut (§ 10.4.2.3(3)). The SLDC's general parking table requires 2.0 off-street spaces per dwelling unit for single-family dwellings (Table 7-6, § 7.10.4); ADUs are not separately listed in that table. The county STR rules separately require all short-term-rental parking to be onsite and cap guest vehicles at the number of onsite spaces.

In the base zoning districts an ADU is processed as an administrative (ministerial) development permit: SLDC § 4.8.1 provides that 'a public hearing is not required' and § 4.8.2.1 requires a development permit for construction of any structure; the county quotes fifteen working days for standard residential permits with a $200 base application fee. Building trades inspections (foundation, framing, electrical, plumbing) and the certificate of occupancy run through the state Construction Industries Division, and the county application includes the state Multi-Purpose Building Application. In the Tesuque and Madrid community overlay districts, however, an ADU requires a discretionary conditional use permit under Chapter 4 (§§ 9.5.5.1, 9.6.5.1), and Los Cerrillos prohibits ADUs outright in its TC and PI overlay zones.

Nothing in SLDC § 10.4 restricts renting an ADU long term. Short-term rental (any period under 30 consecutive days) is licensed under county code § 110.09(H) (Ordinance 2022-07, amended by 2023-08 and 2024-01): an ADU on the same legal lot of record as the owner's primary residence qualifies as an owner-occupied STR, needing an annual business registration ($35 per year per the county FAQ), limited to one owner-occupied registration per owner. Any other ADU STR is non-owner-occupied, requiring a business license ($375 initial, $300 renewal) subject to caps of 3 percent or 7 percent of housing stock in listed Census Designated Places, and no person may hold an interest in more than two STR licenses countywide. Occupancy is capped at 2 people per approved bedroom up to 10 (children 5 and under excluded), STR parking must be onsite, and county lodgers' tax plus state gross receipts tax apply. STRs are also barred where private covenants prohibit them.