Napa Building Permits Guide for Homeowners

Last updated November 13, 2026. Reviewed by the Cash Home Buyers CA team.

The City of Napa has moved permit applications, plan submission, fee payment, inspection scheduling and project tracking into a new online system called NapaON. The city says it replaces the older TRAKiT system and lets applicants do everything from a single account.

This guide explains how a Napa residential permit works, what plan reviewers look for, what the city’s own fee estimates show, how to legalize work built without a permit, and what all of it means if you plan to sell.

Napa permits at a glance

Department	Building Division, Community Development Department, City of Napa
Building Division phone	707-257-9540
Planning Division phone	707-257-9530
Inspection line	707-257-1063
Permit technicians	PermitTechs@cityofnapa.org (listed for minor residential interior remodels)
How to apply	NapaON online portal: submit applications and plans, pay fees, schedule inspections, track status
Fire Prevention	707-257-9590
Sewer (separate permit)	Napa Sanitation District, 707-258-6000 ext. 401
Water	City of Napa Utilities Department, 707-257-9521

Who reviews a Napa permit

A Napa building permit is not reviewed by one desk.

The city’s accessory dwelling unit permit guide explains that the Building Division verifies the health, life safety and energy requirements of the California codes, while Planning, Fire Prevention, Development Engineering, Stormwater, Water and Materials Diversion staff also review the plans.

Sewer connections go through a separate application to the Napa Sanitation District, and the city says approval from the district must be in hand before a permit can be issued.

For homeowners, the practical lesson is to contact each reviewing group early, because a comment from any one of them can restart the clock.

Plan review timelines

For accessory dwelling unit projects, the city’s guide tells applicants to expect the Building Division to take 21 business days to process an application and review the plans, and to expect at least one set of comments requesting more information.

After you respond, it says to expect another 14 business days for the next round. The guide also tells applicants to expect at least two rounds of comments and resubmittals. A soils report may be required if the project sits on an earthquake fault or in a flood zone.

These timelines come from the ADU guide, so treat them as a realistic benchmark for a substantial project rather than a promise for a simple remodel, and ask the Building Division how long your own scope should take.

What to submit

The city’s plan intake checklists give a good picture of what reviewers want to see. For a typical residential addition or ADU, they list:

• A completed residential permit application and the plan check fee.
• Plans drawn to scale and legible on at least 24-inch paper (the guide described paper sets; with NapaON, confirm the current electronic format).
• A cover sheet with the project address, sheet index, a detailed scope of work, applicable codes, occupancy, construction type, number of stories, and the designer’s name and signature.
• A site plan showing a north arrow, property lines and parcel size, every existing and proposed structure, setback distances, and utility connection points.
• At least two building elevations, a dimensioned floor plan listing the use of each room, and cross sections for altered areas.
• Framing and structural details, including foundation, floor, wall and roof framing, plus structural and truss calculations where they apply.
• Mechanical, plumbing and electrical plans showing the main panel, outlets, heating and cooling equipment, water heater and gas piping.
• Signed energy code compliance documents and the city’s Residential High-Performance Building Checklist.
• A fire sprinkler letter from a C-16 licensed contractor, or sprinkler plans under separate cover, when sprinklers are required.

One caution: the checklists in that guide reference the 2019 California codes, so confirm with the Building Division which code cycle applies to a permit you file today.

What the city’s fee estimates show

The ADU guide includes sample fee tables dated January 1, 2022. They are estimates only, they change with local property conditions, and fire fees are added when sprinklers are needed, but they show how a Napa permit is built up.

For a junior ADU of 500 square feet or less, the sample lines include a $697.00 building permit fee, a $460.02 building plan check fee, a $69.70 planning plan check fee, and $180.00 each for plumbing and electrical. For an ADU of 749 square feet or less, the city’s sample total was $2,351.67.

For one of 750 to 1,200 square feet, the sample total was $13,131.17, which added a $2,293.00 park impact fee, a $5,700.00 affordable housing impact fee, a $1,233.00 street improvement fee and a $1,127.00 utility undergrounding fee.

The estimates exclude water impact fees and capacity charges, Napa Valley Unified School District fees (707-253-6281), and sewer fees collected by Napa Sanitation. Because these figures are several years old, ask for a current estimate before budgeting.

Inspections and final approval

Once plans are approved and the sewer permit is verified, the Building Division contacts you that the permit is ready. You pay the remaining fees, begin construction, and complete inspections from each division and agency that reviewed the plans.

The city lists the inspection line as 707-257-1063, and NapaON now lets you schedule inspections online. A certificate of occupancy is the final step for a new dwelling unit. Exterior sewer piping is inspected by Napa Sanitation rather than the city.

Legalizing work built without a permit

Napa publishes a concealed construction verification process for owners of units built without permits.

The city says there is no fine or penalty for legalizing an existing accessory dwelling unit, though you pay the same fees as a new project at the time you submit, and that an inquiry to the Community Development Department to see whether the unit is allowed will not result in code enforcement action.

The work must meet current minimum code, which can mean egress windows in sleeping rooms, openable windows for light and ventilation, and weatherproofing. Because the work is already covered, inspectors may require you to open it up.

The city’s examples include exposing the foundation at three or more locations through a hole of at least two feet by two feet, drilling two three-quarter-inch holes through the slab, exposing anchor bolts and shear hold downs, opening a two-foot-square section of wall covering on each shear wall line, pressure testing interior gas piping at 10 psi for 15 minutes, and air testing drain, waste and vent piping at 5 psi for 15 minutes.

It may also require certification from a licensed contractor for plumbing, electrical or mechanical work. Budget for that opening-up and repair cost before deciding whether legalizing makes sense.

Permits and selling a Napa house

Permit history matters at sale time. Buyers, lenders and appraisers ask whether additions, garage conversions and remodels were permitted, and California sellers generally disclose known unpermitted work.

Our statewide guide to selling as-is with unpermitted work explains the disclosure rules, and the seller closing costs guide covers what else to budget.

If you own a Napa home with open permits, expired permits or unpermitted additions, you generally have three paths: close out the permits before listing, disclose and discount the price on the open market, or sell as-is to a cash buyer. A short checklist before you decide:

• Pull your permit history from the city and note anything open or expired.
• List improvements made without a permit, such as converted garages, enclosed porches or added bathrooms.
• Gather final inspection records and invoices for permitted work.
• Ask the Building Division what legalizing each item would take, including plans, fees and opening-up work.
• Compare that cost and timeline with a no-repairs cash sale.

How to sell a house in Napa

1. Review which work on the property was permitted and which was not.
2. Collect permits, final inspection records and any city notices.
3. Request a no-obligation cash offer for the house as it stands.
4. Choose your closing date.
5. Close with no repairs, permit cleanup or showings required.

Our local pages cover related situations in Napa, including selling as-is, selling fast and the cash offer process.

Frequently asked questions

How do I apply for a building permit in Napa?

The city says to use NapaON, its online system for submitting applications and plans, paying fees, scheduling inspections and tracking your project.

How long does Napa plan review take?

The city’s ADU guide says to expect 21 business days for the first review cycle and 14 business days after you respond to comments, with at least two rounds of comments likely.

Is there a fine for legalizing an unpermitted ADU in Napa?

The city says there is no fine or penalty for legalizing an existing accessory dwelling unit, but you pay the same fees as a new unit, and an initial inquiry will not trigger code enforcement.

Do I need a separate sewer permit in Napa?

Yes for many projects. Napa Sanitation District runs its own review, and the city requires its approval before issuing a permit. Call 707-258-6000 ext. 401.

How do I schedule a Napa inspection?

Use NapaON or call the city’s inspection line at 707-257-1063.

Can I sell my Napa house with unpermitted work?

Yes. You can disclose it and sell as-is, including to a cash buyer. Our statewide guide explains the disclosure rules.

More guides

• We Buy Houses in Napa
• We Buy Houses in Napa County
• Napa County Property Tax Guide
• Napa Code Enforcement Guide
• Napa Zoning and ADU Guide
• All California Guides

Sources

• City of Napa: Permits and Plan Review Information
• City of Napa: ADU How-To Permit Guide for Homeowners
• City of Napa: NapaON announcement

This guide is general information from public sources, not legal advice. Confirm current rules with the city.