ADU rules in Washoe County

Detached accessory dwellings are allowed in the rural and lower density suburban zones (LDR, MDR, HDR, LDS, GR, GRA) and in Medium Density Suburban, but Table 110.302.05.1 shows a flat dash for High Density Suburban and for all three urban residential zones (LDU, MDU, HDU), so a detached backyard unit is simply unavailable there even though single-family homes are. Two gates bite elsewhere: the parcel must be at least 12,000 sq ft (about 0.28 acre), and on any parcel half an acre or smaller, plus every MDS parcel regardless of size, an Administrative Review Permit under Article 809 must be approved before the building permit. Only one accessory dwelling unit or guest quarters is allowed per parcel, and neither is allowed on parcels with cottage court or multifamily development. In the Tahoe Planning Area (Incline Village and Crystal Bay) Section 110.220.85 layers TRPA Code Section 21.3.2 on top and requires an administrative review permit in every case.

Attached accessory dwellings are marked 'A' (allowed by right) in every residential regulatory zone from Low Density Rural through High Density Urban, plus General Rural and General Rural Agricultural, so an internal conversion, a basement unit or an addition moves on a building permit with no discretionary review. The conditions are routine: a main residential unit must already exist, the parcel must be at least 5,000 sq ft, and the unit must meet the zone's setback and height standards and the Article 406 lot coverage limits. To count as attached the unit must abut the habitable space of the main dwelling or the ceiling of an attached garage, and its exterior entrance may not sit on the same wall as the main entrance; a trellis, deck, patio or breezeway does not make a unit attached. Only one accessory dwelling unit or guest quarters is permitted per parcel.

Ordinance 1753, effective January 23, 2026, raised the percentage cap from 50% to 80% of the main dwelling for both attached and detached units. Detached units are capped at 1,500 sq ft or 80% of the main dwelling, whichever is smaller, except in Medium Density Suburban where the ceiling drops to 1,200 sq ft; attached units use the same 1,500 sq ft and 80% rule except in MDS, High Density Suburban and all urban zones, where 1,200 sq ft applies. On parcels holding a duplex, triplex or quadplex either type is limited to 800 sq ft. Garages, crawl spaces, cellars, attics and basements not designed for human occupancy are excluded when measuring the main dwelling, and a variance may not be used to exceed the detached cap (the one exception is converting a guest house legally built before May 26, 1993). A 'minor accessory dwelling unit' is a detached unit under 500 sq ft and earns 5 ft side and rear setbacks at 12 ft of height or less. The Tahoe Planning Area was not moved to 80%: Section 110.220.85 still caps units at 50% of the main dwelling or 1,500 sq ft on parcels of an acre or more, and 1,200 sq ft on smaller parcels.

Neither Section 110.306.20 nor Section 110.306.25 conditions an accessory dwelling on the owner living on the property, and the Article 304 use-type definitions impose no occupancy test either. The county's own ADU Hub FAQ confirms the point in plain language, stating that Washoe County does not restrict the occupancy of an ADU to family members. The deed restrictions that do appear in Article 306 serve a different purpose: they attach to detached accessory structures and guest quarters that connect to water or sewer, to stop them being converted into dwelling units without a permit, and the Planning and Building Division releases them when the structure is legally converted to an ADU. The one owner-linked rule in the picture is a short-term rental rule rather than a zoning rule: an STR permittee must be the property owner.

Table 110.410.10.1 requires one off-street space per attached accessory dwelling and one per detached accessory dwelling, in addition to the spaces the main dwelling already needs, and Sections 110.306.20(g) and 110.306.25(g) restate that a minimum of one space shall be added. Those subsections reserve the possibility of additional parking beyond that one space 'pursuant to the provisions of Article 410', but the Article 410 table sets the accessory dwelling requirement at exactly one, so one space is the operative number. Minor accessory dwelling units under 500 sq ft need no off-street space at all on parcels larger than half an acre; on parcels of half an acre or smaller they need one space unless the Director of Planning and Building waives it through a director's modification of standards. In the Tahoe Planning Area one space is required in addition to the primary use's parking, and tandem parking counts.

The review path turns on the ADU type, the zone and the parcel size. An attached unit is an allowed use ('A') in every residential zone, so it needs only a building permit. A detached unit is allowed by right on parcels larger than half an acre in LDR, MDR, HDR, LDS, GR and GRA; the dagger in Table 110.302.05.1 means administrative review is required on parcels half an acre or smaller. In Medium Density Suburban the table reads 'AR', an Administrative Review Permit in every case, and in High Density Suburban and the urban zones a detached unit is not allowed at all. An Article 809 administrative review is a written staff decision by the Planning and Building Director: no public hearing is held, but owners within 500 feet are noticed and get 15 calendar days to file written testimony, the applicant gets 7 days to respond, and the Director may approve, condition, modify or deny the request, with appeals to the Board of Adjustment. Tahoe Planning Area accessory dwellings always require an Article 809 permit and separate TRPA review.

Article 306 places no limit on renting an accessory dwelling: there is no minimum lease term, no family-occupancy test and no owner-occupancy condition. Renting for less than 28 days is a short-term rental and requires a Washoe County STR permit under Article 319, renewed and re-issued annually, with a passed physical inspection, a local responsible party reachable 24/7 within 30 minutes, at least $500,000 of liability coverage, and room tax paid to the Reno-Sparks Convention and Visitors Authority. Only one STR is permitted per parcel, except that a second STR may be allowed on properties outside the Tahoe planning area if it is established in a legally permitted attached or detached accessory dwelling. Effective October 14, 2024, newly permitted STRs may not be established in ADUs within the Tahoe planning area; permits issued there before that date stay valid only while the parcel's ownership is unchanged. An ADU cannot be sold off separately: a detached unit becomes a main dwelling only by subdividing the parcel, and the resulting parcels must satisfy every Development Code standard.