Napa County · Building on your lot

Building on your lot in Napa County

Napa County's code applies only in unincorporated areas of the county. It sets fence heights, rear-yard accessory-building limits and home-business rules, including limits on wine-related uses.

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Key points

Fence height: County rule: fences are limited to 4 ft in front yard setbacks and 8 ft in side and rear setbacks, see-through above 6 ft.
Accessory buildings: County rule: rear-yard garages and accessory buildings are limited to 15 ft at the ridgeline and 50% of the rear yard.
Home businesses: County rule: a home business may use 25% of the home's floor area, is run by residents only, and needs an administrative permit.

Each rule below is marked Napa County code or CA state law and links to the section it comes from (checked October 2026). General information, not legal advice.

Napa County's code applies in the unincorporated areas of the county. Cities in Napa County have their own codes and their own pages.

Fences and walls

Napa County code What Napa County's code adds
Corner visibility	Solid fences may be no more than 42 inches high within a 55-foot corner vision triangle. Applies: At intersections and driveway entrances, in all districts. § 18.104.270 · code text At intersections and driveway entrances, solid fence height in all districts shall not exceed forty-two inches in height within a fifty-five foot corner vision triangle
Front yard height	Up to 4 feet. Applies: In the designated front yard setback. § 18.104.270 · code text Fences up to a height of four feet are permitted in the designated front yard setback Up to 8 feet. Applies: See-through deer fencing that supports agricultural uses, in the designated front yard setback. § 18.104.270 · code text see-through deer fencing up to eight feet is permitted to support agricultural uses
Side and rear yard height	Up to 8 feet. Applies: Side and rear yard setbacks; above 6 feet the fence must be see-through, such as wire or lattice, unless a fence permit is granted. § 18.104.270 · code text Fences up to eight feet in height are permitted in side and rear yard setbacks.
Permit	Yes. A fence permit is required. Applies: A fence that needs a building permit and is in the road setback. § 18.104.270 · code text No structure (i.e., a fence requiring a building permit) shall be located within the road setback unless a fence permit is obtained

Sheds, garages and other accessory structures

Napa County code What Napa County's code adds
Maximum height	No more than 15 feet at the ridgeline. Applies: Detached garages, accessory buildings or solar panel systems in a rear yard. § 18.104.140 · code text a detached garage, accessory building, or solar panel system not exceeding fifteen feet in height at the ridgeline may occupy not more than fifty percent of the area of a rear yard.
Size or lot coverage	No more than 50% of the rear yard area. Applies: Detached garage, accessory building or solar panel system up to 15 feet tall at the ridgeline. § 18.104.140 · code text a detached garage, accessory building, or solar panel system not exceeding fifteen feet in height at the ridgeline may occupy not more than fifty percent of the area of a rear yard.
Side and rear setback	At least 5 feet from the side and rear lot lines. Applies: Rear-yard accessory structure up to 15 feet tall that is at least 70 feet from any street. § 18.104.140 · code text If such a structure is situated not less than seventy feet from any street it may be located not closer than five feet from the side and/or rear lot lines. At least 20 feet from the side and rear property lines. Applies: Structures accessory to agriculture, other than fences, in the residential country zoning district. § 18.104.140 · code text structures in the residential country zoning district accessory to agriculture, other than fences, shall be located at least twenty feet from the side and rear property line and fifty feet from the front property line.
Distance from the house	At least 8 feet from the main building. Applies: Garage, carport or other accessory building that does not share a wall with the main building. § 18.104.140 · code text A garage, carport or other accessory building not having a common wall with the main building shall not be placed closer than eight feet from the main building.

Running a business from home

Napa County code What Napa County's code adds
Space used	No more than 25% of the home's gross floor area. § 18.104.090 · code text not more than twenty-five percent of the gross floor area of the dwelling unit shall be used in the conduct of the home occupation.
Employees	Only people who regularly live on the premises. § 18.104.090 · code text No person other than those persons who are regular residents on the premises shall be engaged in such occupations.
Permit	Yes. An administrative permit must be issued first. § 18.104.090 · code text No home occupation shall be allowed unless an administrative permit has first been issued for such use pursuant to Chapter 18.126.
Businesses not allowed	storage, warehousing or manufacturing of wine for sale on the premises when annual wine production, manufacturing and storage is two hundred gallons or more Applies: wine-related use on the premises or within an accessory structure located within five hundred feet of the residence § 18.104.090 · code text Storage, warehousing or manufacturing of wine for sale on the premises is allowed only if the annual wine production, manufacturing and storage on the premises or within an accessory structure that is located within five hundred feet of the residence on the premises is less than two hundred gallons.

Lot splits under SB 9

Napa County code What Napa County's code adds
Owner occupancy	The applicant signs an affidavit to live in 1 new unit as their main home for at least 3 years. Applies: Does not apply to a community land trust or qualified nonprofit corporation. § 17.17.030 · code text The applicant for an urban lot split shall sign an affidavit, in the form approved by county counsel, stating that the applicant intends to occupy one of the housing units on the newly created lots as its principal residence for a minimum of three years from the date of the approval of the urban lot split.

Solar panels and EV chargers

Napa County code What Napa County's code adds
EV charger permit	Apply in person, by mail or electronically; a complete, checklist-compliant application is approved administratively with all required permits. Applies: Projects that comply with the EV charging station checklist. § 15.15.050 · code text For projects that comply with the electric vehicle charging station checklist, the applicant may submit the permit application and associated documentation to the county's building division by personal delivery, mail, or electronic submittal.
Solar permit process	Expedited review, electronic submittal allowed; complete applications meeting checklist and standard plan get a permit as soon as reasonably practicable. Applies: Small residential rooftop solar energy systems eligible for expedited review. § 15.14.100 · code text As soon as reasonably practicable, upon receipt of a complete application and all required supporting documentation that meets the requirements of the standard plan and checklist, the building official or designee shall issue a building permit or other nondiscretionary permit. Electronic submittal is allowed; wet signatures or hard-copy signature pages are required. Applies: Small residential rooftop solar energy system permits. § 15.14.090 · code text Electronic submittal of the required permit application and documents shall be allowed for all small residential rooftop solar energy system permits pursuant to the electronic submittal procedures specified in the checklist of requirements referenced in subsection (A) of Section 15.14.090.

Other Napa County rules on this

Napa County's code also has these chapters. We have not summarized their values on this page yet; read them in the library.

Keeping bees (apiaries) (§ 6.12.020)
Limits on keeping roosters (§ 6.18.030)
Truck and RV parking on residential streets (§ 10.08.080) — on public streets in residential areas

Who this affects

HomeownersContractorsDesigners

Frequently asked questions

How tall can a fence be in Napa County?

County rule: fences are limited to 4 ft in front yard setbacks and 8 ft in side and rear setbacks, see-through above 6 ft.

How big can a shed or accessory building be in Napa County?

County rule: rear-yard garages and accessory buildings are limited to 15 ft at the ridgeline and 50% of the rear yard.

Can I run a business from my home in Napa County?

County rule: a home business may use 25% of the home's floor area, is run by residents only, and needs an administrative permit.

Can I split my lot under SB 9 in Napa County?

Napa County's code: The applicant signs an affidavit to live in 1 new unit as their main home for at least 3 years. (Does not apply to a community land trust or qualified nonprofit corporation.) (§ 17.17.030).

Do I need a permit for solar panels or an EV charger in Napa County?

Napa County's code: Apply in person, by mail or electronically; a complete, checklist-compliant application is approved administratively with all required permits. (Projects that comply with the EV charging station checklist.) (§ 15.15.050); Expedited review, electronic submittal allowed; complete applications meeting checklist and standard plan get a permit as soon as reasonably practicable. (Small residential rooftop solar energy systems eligible for expedited review.) (§ 15.14.100).

General information, not legal advice.

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Napa County Municipal Code — full text

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Napa County overview