ADU Contractor in Napa County

We serve six Bay Area counties — Alameda, Contra Costa, Marin, Napa, San Mateo, and Santa Clara — covering 47 cities from Oakland to San Jose. Our crews are based in Castro Valley, putting us within 45 minutes of every city we serve. We handle permits and know the building codes for each jurisdiction, which matters because requirements and fees vary significantly between cities.

We offer $0-down financing with approved credit, 12-month same-as-cash plans, and extended terms up to 15 years for larger projects. You only pay for completed, inspected work — we never ask for full payment before the job is done. Your project manager will walk you through every option during your estimate appointment. We also accept checks, ACH, and all major credit cards.

Yes. CSLB License #1078806 — verify it anytime at cslb.ca.gov. We carry $2M general liability, full workers’ comp, and are bonded per California law. We hold GAF Master Elite, Owens Corning Preferred, CertainTeed ShingleMaster, and James Hardie Elite Preferred certifications — each requires annual training and quality audits to maintain. We’re happy to provide proof of insurance before any work begins.

Most exterior projects in the Bay Area require a building permit. Fees vary by city — Oakland runs $200–$600, Peninsula cities often more. We handle the entire permit process: application, plan submission, and scheduling inspections. Permit fees appear as a separate line item in your estimate so you’ll see every cost upfront. For homes in WUI fire zones (Berkeley Hills, Oakland Hills, parts of Marin), we ensure full compliance with local fire-rated material requirements.

ADU costs in Napa County vary by city — from Napa to Yountville. With median home values averaging $1,414,000 across the county, we see a range of project scopes. Hamilton Exteriors provides free, itemized estimates for every Napa County project with no hidden fees.

California's ADU laws make it possible to build on most residential lots in Napa County. Napa County has streamlined the permitting process. We evaluate your property's potential during our free consultation, including setbacks, utility access, and local zoning.

From design to move-in, most ADU projects in Napa County take 8-12 months. The Napa County permitting process typically takes 60-90 days, and construction runs 4-6 months. Our 60-day permit guarantee keeps your timeline on track.

Yes. We handle all ADU permitting in Napa County and throughout Napa County — architectural plans, structural engineering, Title 24 energy compliance, and city submissions. Our 60-day permit guarantee means we manage the entire process.

In Napa County, you can build detached ADUs (up to 1,200 sq ft), garage conversions, attached additions, and junior ADUs (up to 500 sq ft). Many homeowners in Calistoga are choosing detached ADUs for rental income or multi-generational living.

After the devastating 2017 Atlas and Tubbs fires and the 2020 Glass Fire, Napa County adopted strict fire-hardening rules for the Wildland-Urban Interface (WUI). Homes in Napa's fire zones must use Class A fire-rated roofing, ember-resistant vents, non-combustible siding within 6 feet of grade, and tempered or dual-pane windows. Hamilton Exteriors is experienced with Napa County's fire rebuild and hardening requirements — we ensure every material selection and installation detail meets current Cal Fire and local codes.

Napa Valley's distinctive character does influence exterior choices, but not through formal restrictions for most residential projects. Napa homeowners often choose materials that complement wine country architecture — earth-toned James Hardie siding, natural stone accents, and architectural shingles in weathered-wood or slate tones. Hamilton Exteriors offers a full range of colors and textures that blend with Napa's aesthetic. For properties in or near vineyard zones, we can advise on any county-specific overlay requirements.