Lyon County, NV Accessory Structures: ADU Rules (2026)

Chapter 15.311 governs the county's Rural Residential districts, which cover large-lot unincorporated areas such as Dayton, Silver Springs, Stagecoach and the Smith and Mason Valleys. In the RR-20 district, section 15.311.01(F)(2) permits accessory dwelling units at a density of no more than one unit per twenty gross acres, and each ADU beyond one per parcel is permitted specifically to house employees or family members engaged in agricultural pursuits on that land. The unit's floor area is capped at one thousand one hundred (1,100) square feet or fifty percent of the primary residence's livable space, whichever is less, so a smaller main house yields a smaller allowed ADU.

Every dwelling, main house and accessory unit alike, must be served by its own individual well and septic system rather than sharing one system, and units must be separated from each other by no less than fifty feet (50'). An ADU itself cannot be used as the base for adding yet another accessory dwelling unit; the county caps density at the one-per-twenty-acre figure regardless of how a parcel is subdivided in practice. Lyon County Code section 15.335.03(A)(1) layers on additional performance-based standards that every ADU must satisfy before Community Development issues a building permit.

Smaller rural residential zones (RR-10, RR-5, RR-2, RR-1) carry their own parallel ADU density ratios tied to each zone's minimum lot size, so the twenty-acre ratio described here applies only within RR-20.