ADU Rules in Napa County, California

We track 1 city in Napa County. Each city writes its own ADU ordinance on top of California law, so size limits, fees, and design rules differ from one city to the next.

Cities

Max Detached Size

1,200 sq ft

Build Costs From

$175,000

Pre-approved Plans

0 of 1 cities

Napa County Cities Compared

City	Max detached	Height	Permit fees	Build cost
Napa	1,200 sq ft	Per Gov. Code 66321(b)(4): 16 ft detached (18 ft near major transit), 25 ft attached	$8,000 – $16,000	$175,000 – $355,000

Napa ADU rules

Napa reviews ADUs ministerially through its Community Development Department and caps new ADUs at 1,200 sq ft. Its Junior Unit Initiative Program offers technical help and forgivable financing of up to $50,000 to create a JADU or conversion ADU. Short-term rental rules limit vacation use, and lots near the Napa River should check flood maps early.

Rules that apply in every California city are summarized in our California ADU law guide. See all California cities or compare every city side by side.