ADU Surveys in Napa, CA

Napa keeps ADU permitting ministerial. The city's ADU permit guide states that to build an ADU you only need a building permit, with two exceptions that send a project to the Planning Division: detached ADUs over 16 feet tall, and ADUs involving exterior changes to properties on the Historic Resources Inventory. The building permit itself is not casual, though. Seven plan sets go out to Building, Planning, Fire Prevention, Development Engineering, Stormwater, Water, and Materials Diversion simultaneously, with a 21-business-day first review cycle, and the intake checklist adds a plan set if the project is in the flood plain and another if construction valuation exceeds $100,000. Napa Sanitation runs its own separate review and permit.

The site plan items on that checklist are survey content: property lines and lot boundaries with parcel size, the location of all structures distinguished as existing or proposed, setback distances from the property lines to the existing dwelling, the proposed ADU, and other structures such as detached garages, finished floor elevations, and existing and proposed utility lines and connection points. Detached new construction must sit at least four feet from the property line, and attached units follow the underlying zoning district setbacks, so the line itself has to be right rather than approximated from a fence. The guide also notes that a soils report may be required if the project is on an earthquake fault or in a flood zone, and directs applicants to raise site constraints such as steep slopes and agricultural buffer setbacks with Planning before design.

Those constraints track Napa's geography. Alta Heights and Browns Valley bring the slopes; parcels near the Napa River and Napa Creek bring the flood plain set and the elevation questions; the 2014 South Napa earthquake on the West Napa fault is a reminder of why fault proximity shows up on the soils note. One laser-scanned site visit answers all of it: boundary resolved from the record, structures and utilities located, setbacks dimensioned, and elevations tied to NAVD88. Deliverables are a stamped site plan base map, layered DWG, and staked corners. See also our Napa topographic surveys and the Bay Area ADU survey requirements guide.