Napa's Winery Definition Ordinance: What It Allows, What It Means
Napa County’s Winery Definition Ordinance (WDO), Ordinance No. 947, adopted January 23, 1990, defines a winery in the county’s agricultural areas as an agricultural processing facility for turning grapes into wine, and treats tours, tastings, retail sales and marketing as uses that must stay accessory to that production. For wineries approved or expanded after that date, it also requires a parcel of at least 10 acres for a new winery, at least 75% of grapes from Napa County, and accessory structures no larger than 40% of the production area, as summarized by the 2014-15 Napa County Grand Jury.
For a buyer, the WDO matters because it decides what a winery property can legally do, and that is a large part of what it is worth. Two wineries with similar buildings can have very different rights depending on when they were permitted and what their use permits say. This guide explains the rules, the permit “vintages” and what to check before you make an offer. It sits alongside our guides to the Napa Valley appellation and Agricultural Preserve and Agricultural Watershed zoning.
Why Napa adopted the WDO
Napa County created its Agricultural Preserve in 1968. The Grand Jury describes the WDO as the ordinance that defines which winery activities are permitted under that preserve. According to its report, it regulates winery size, location, signage, tours and tastings, production capacity, grape sourcing, special events and retail sales, and it does not allow non-winery commercial development.
The ordinance has been amended since. Ordinance No. 1340, adopted May 11, 2010, addressed the marketing of wine, food and wine pairings during tours and tastings, and the sale of wine and wine-related products. County planning staff described those 2010 changes as updating “but not substantively” changing the 1990 provisions.
The WDO rules at a glance
| Rule | What it says | Question for a buyer |
|---|---|---|
| Definition | A winery is an agricultural processing facility for fermenting and processing grape juice into wine | Is the main activity on site actually production? |
| Minimum parcel | 10 acres for a new winery; many older wineries sit on smaller parcels | Is the parcel large enough if you plan a new winery? |
| Grape sourcing | At least 75% Napa County grapes for wineries new or expanded after January 23, 1990; for a pre-1990 winery that expands, the rule applies to the added production | Where does the fruit come from today, and does it fit your plans? |
| Accessory structures | No more than 40% of the area used for wine production | How much of the building is tasting, hospitality or office space? |
| Accessory uses | Marketing, tours and tastings must remain accessory to production; products sold must be wine-related | What do the use permit’s conditions allow? |
| Number of wineries | No legal cap on the number of wineries in the county | Competition for visitors and permits continues to grow |
Don’t confuse the WDO’s 75% rule with the federal rules for putting a county or AVA name on a label. The WDO rule governs the grapes a post-1990 winery processes, whatever its labels say; our appellation guide covers the label rules.
Permit vintages: pre-1974, pre-WDO and post-WDO wineries
The single most useful question about a Napa winery is when, and under what, it was approved. The Grand Jury and county staff reports describe these categories:
- Wineries operating before July 31, 1974. Wineries legally operating before that date did not need a use permit to continue. Any change in activities or expansion of production requires a use permit that conforms to current rules.
- Pre-WDO wineries. Wineries permitted before January 23, 1990 operate under the terms of their original use permits, and those terms vary. Permits from the 1970s are often far less detailed than modern ones, which has led to disputes over what visitation they allow.
- Post-WDO wineries. Wineries approved after January 23, 1990 operate under use permits written to the WDO, including the 75% rule and specific limits on production, visitors and marketing events.
- Small winery exemptions. Some small wineries operate under a certificate of exemption rather than a full use permit. The Grand Jury notes that expanding one requires meeting the full WDO requirements.
Older rights can be valuable, but they are only as clear as the documents behind them. Napa County has litigated with wineries over what older permits allow; in one case over a winery with a 1979 permit, the dispute turned on a handwritten condition and whether by-appointment visits were limited. In May 2026, trade coverage described several producers facing county lawsuits over how the 1990 ordinance applies to practices they had used for years.
Operating beyond what a permit allows carries real risk. In one county enforcement case (Napa County Superior Court case no. 22CV001262), the county alleged that a winery was operating without a valid use permit. On February 20, 2025 the court issued a preliminary injunction, an interim order made before any final decision, restricting winery activities at the property until a valid use permit is obtained. The county filed a proposed judgment in January 2026. A proposed judgment is a request to the court, not a ruling, and we have not confirmed that a final judgment has been signed and entered, so check the court record for the current status.
Tours, tastings and marketing events
Under the WDO, visitation is not a right that comes with the zoning; it is what the individual use permit authorizes. Permits typically set:
- Tours and tastings, often by prior appointment, with daily and weekly visitor limits. A 2010 use permit application on a Planning Commission agenda, for example, proposed tours and tastings by prior appointment with a maximum of 18 visitors a day.
- Marketing events, by number per year and maximum attendance. The county code defines “marketing of wine” in section 18.08.370, and the 2010 amendment clarified where, when, how and for whom winery marketing may occur.
- Food and wine pairings, which the 2010 amendment addressed as part of tours and tastings.
- Retail sales, limited to wine and wine-related products.
The county audits compliance. In a 2014 review of 20 wineries’ 2013 production and visitation, staff reported that five were pre-WDO, twelve were permitted for tours and tastings “By Appointment Only,” and eight were out of compliance for visitation. The Grand Jury reported that about 20 wineries were audited each year and that the share of audited wineries out of compliance on at least one item rose from 29% in 2011 to 40% in 2013. Penalties are decided case by case and can include fines and production limits.
Tastings on a vineyard without a winery
County rules have required growers to have a winery to hold tastings on their farms. In December 2025, the Board of Supervisors approved an 18-month pilot, beginning in January 2026, for vineyard tasting events under state law (AB 720), according to the Napa Valley Register. Events need a state estate tasting event permit and a county permit, are capped at 49 guests and must stay within the traffic limits for farms on agricultural roads. If a vineyard without a winery is on your list, check the current status of the pilot.
Production limits and the 75% rule in practice
A Napa use permit sets a production total, in gallons, for the winery’s own wine and any custom crush for other brands. The Grand Jury noted that wineries don’t always produce or host what their permits allow, and county audits check production against the permitted total.
The 75% rule shapes what a buyer can do with the business. If you plan to bring in fruit from Sonoma, Lake or Mendocino, the share you can process at a post-WDO winery is limited, and county staff have noted that the rule “does not offer any options.” Fruit supply also depends on contracts; see our guides to grape purchase agreements and custom crush and alternating proprietorships.
What to check before you buy a Napa winery
- The full permit history: the original use permit or exemption, every modification, and the conditions of approval for each.
- Permitted limits: annual production, daily and weekly visitors, number and size of marketing events, hours, and any food service terms.
- Actual operations compared with those limits, including the last few years’ visitor and event records and production reports.
- Compliance history: any county audit results, notices of violation or code enforcement files.
- Grape sourcing records showing how the winery meets the 75% rule, if it applies.
- Building areas: production space against accessory space, to see where the 40% limit stands.
- Water and wastewater: any Water Availability Analysis and wastewater permits tied to the use permit; see our guides to Napa groundwater rules and winery wastewater.
- Whether the permit rights will carry over to you as the new owner, which you should confirm with the county and a land-use attorney.
Our winery due diligence checklist puts these items with the licensing, equipment and title review, and our guide to winery valuation explains how permit rights feed into price. If you plan a new winery or an expansion, our guide to the Napa winery use permit covers the application process.
This is general information, not legal advice; talk to a California land-use attorney or a Napa County planner about a specific property’s permits.
Questions people ask
What is the Napa Winery Definition Ordinance?
Napa County’s 1990 ordinance (No. 947) that defines what a winery is in the county’s agricultural areas and limits accessory activities such as tours, tastings, marketing and retail sales. It also set a 10-acre minimum for new wineries and a 75% Napa County grape rule.
What is the WDO 75% rule?
Wineries approved or expanded after January 23, 1990 must source at least 75% of their grapes from Napa County. For an older winery that expands, the rule applies to the added production.
Can I build a winery on less than 10 acres in Napa County?
Not a new winery under the WDO’s standard rules, which set a 10-acre minimum parcel. Some smaller existing wineries operate under older permits or a small winery exemption.
Are Napa winery tastings by appointment only?
It depends on the use permit. Many permits allow tours and tastings by prior appointment with visitor limits, while some older wineries have different terms.
What is a pre-WDO winery?
A winery permitted before January 23, 1990, which operates under its original permit terms rather than a WDO-era permit. Wineries operating before July 31, 1974 did not need a use permit to continue, but any change or expansion needs one.
Can I hold tastings at my vineyard if I don’t have a winery?
Under a county pilot that began in January 2026, growers can hold a limited number of vineyard tasting events with state and county permits and a 49-guest cap. Confirm the pilot’s current terms with the county.
Does the WDO limit how many wineries Napa can have?
No. The Grand Jury reported there is no legal limit on the number of wineries; each one needs its own permit and suitable land.
Winery rights are a big part of what you pay for in Napa. When you are considering a winery property, our vineyard and winery team can help you assemble the permit file and compare it with how the property actually operates before you set a price.
Sources & notes
- Napa County Grand Jury 2014-2015: Are Napa County wineries following the rules? (May 12, 2015)
- Napa County Planning Commission: April 21, 2010 agenda, winery ordinance amendments (P10-00098-ORD)
- Napa County Planning Commission: 2013 winery production review (August 6, 2014)
- Napa County: Preliminary injunction, Napa County Superior Court case no. 22CV001262 (February 20, 2025)
- Napa County: Proposed judgment, case no. 22CV001262 (file-stamped January 27, 2026)
- Napa Valley Register: Napa’s Bremer case may have larger winery visitation implications
- Napa Valley Register: County approves vineyard tasting pilot (December 16, 2025)
- Vinetur: Napa County escalates fight over winery tastings (May 11, 2026)
Last reviewed October 2026 by Matthew Martinez.
