ADU Rules in Reno, Sparks & Washoe County (2026): Can I Build One?

Updated October 2026. Looking for the news story on Reno’s ordinance? See Reno’s ADU Ordinance, One Year Later.

When I first wrote this post in 2018, after Amazon invested in prefab ADU builder Plant Prefab, the answer to “Can I put a backyard cottage on my lot?” was probably not for most local homeowners. That has changed. Reno adopted a citywide ADU ordinance in October 2025, Washoe County loosened its rules in 2024 and again in 2026, and a 2025 state law (AB 396) now requires Nevada’s largest cities and counties to allow them.

The catch: the rules depend on which government controls your parcel, and a Reno mailing address doesn’t tell you that. Here’s how to figure out which rules apply to you, and what they say.

What Is an ADU?

An accessory dwelling unit (ADU) is a second, independent home on the same lot as a single-family house: a backyard cottage, casita, garage apartment, or in-law suite. It can be detached (a separate building) or attached (an addition or a converted part of the house). It has its own kitchen, bathroom and entrance, but it can’t be sold separately from the main home.

Step 1: Which Rules Apply to Your Property?

Many homes with a “Reno, NV” address are actually in unincorporated Washoe County (parts of the South Valleys, Galena, Spanish Springs, Cold Springs and Washoe Valley, for example). Those parcels follow county rules, not City of Reno rules.

• Look up your parcel on the Washoe County Assessor’s site. The record shows the jurisdiction and the zoning.
• Note your lot size and the size of your main home (living area, not the garage). Most limits are based on those two numbers.
• Check your HOA’s CC&Rs. Reno’s ordinance says ADUs can’t conflict with private restrictions, so an HOA rule can still be a hurdle.

Step 2: The Rules Side by Side

Sources: City of Reno ADU Guide (rev. 10/13/25); Sparks Municipal Code 20.03.003; Washoe County Development Code Article 306, as amended by Ordinance 1753 (effective Jan. 23, 2026).

A note on Sparks

Sparks’ ADU rules date to 2015. AB 396 required Nevada’s largest cities, including Sparks, to have an ordinance consistent with the new state standards by July 1, 2026, and some of Sparks’ older limits may need to change as a result. Before you design anything in Sparks, confirm the current rules with City of Sparks Planning.

Lake Tahoe (Incline Village and Crystal Bay)

Tahoe Basin properties also fall under the Tahoe Regional Planning Agency, and the state ADU law doesn’t apply there. Washoe County also prohibits new short-term rentals in ADUs in the Tahoe planning area. Expect stricter limits and a longer process; start with Washoe County Planning and TRPA.

What the State Law (AB 396) Changed

Since July 1, 2026, Nevada requires Washoe and Clark Counties and the cities of Reno, Sparks, Las Vegas, Henderson and North Las Vegas to allow ADUs on single-family residential property. Their ordinances can’t:

• Ban a separate kitchen in the ADU.
• Require more than one additional parking space, if existing and street parking are adequate.
• Require side or rear setbacks stricter than the main home’s.
• Prohibit renting the ADU long-term. (Local governments can still ban short-term/transient rentals.)

The law also says ADUs must meet residential building codes, not commercial codes (so no commercial fire-sprinkler requirements). Read the enrolled bill.

What Does an ADU Cost Besides Construction?

Construction cost depends on size, site work and whether the unit is site-built, modular or a conversion. Get bids before you get attached to a plan. Don’t forget government fees. In the City of Reno, the City’s ADU guide lists approximately:

• Regional road impact fee: about $3,700
• Park fee: $800–$1,000
• Police impact fee: $100–$140
• Sewer connection fee: $8,744–$13,235, depending on the unit

That’s roughly $13,000–$18,000 before building-permit and plan-review fees, which are based on project valuation. Fees change, so verify at permit time. You may also need new water, power or gas service. Contact TMWA and NV Energy early. In the county, if you’re on a well, a detached ADU needs a water meter, and septic systems need Northern Nevada Public Health approval.

Hiring an ADU Builder in Reno

Many people searching for ADU rules are really shopping for a builder. A few questions to ask any contractor or prefab company:

• Have you permitted an ADU in my jurisdiction? Reno, Sparks and the county each have their own process.
• Is your Nevada contractor’s license active? Check it on the Nevada State Contractors Board site.
• What’s included? Ask for design, permits, foundation, utility connections and site work as separate line items. On prefab units, the “base price” often leaves these out.
• Who handles the permit? And what is the realistic timeline from first drawing to final inspection?
• Can I see a finished local project? And talk to that owner.

Does an ADU Add Value?

A legal, permitted ADU can add rental income, room for family, and appeal to buyers looking for multigenerational space. How much value it adds at resale depends on the neighborhood, the quality of the unit, and comparable sales, which are still limited locally because Reno’s ordinance is new. An unpermitted unit can be a liability when you sell. If you’re curious which areas have the most ADU-friendly lots, see Which Reno Neighborhoods Are Best Suited for ADUs?

Next Steps

1. Confirm your jurisdiction, zoning and lot size on the Assessor’s site.
2. Talk to a planner: planning@reno.gov (Reno), City of Sparks Planning, or Washoe County Planning & Building.
3. Get two or three builder bids with fees and utility work included.
4. Run the numbers: total cost vs. expected rent or family use.

This post is general information, not legal advice. ADU rules change; always confirm current requirements with the city or county before you design, buy or build.