ADU Contractor in Alameda 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 Alameda County vary by city — from Oakland to Alameda. With median home values averaging $1,228,000 across the county, we see a range of project scopes. Hamilton Exteriors provides free, itemized estimates for every Alameda County project with no hidden fees.

California's ADU laws make it possible to build on most residential lots in Alameda County. Alameda 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 Alameda County take 8-12 months. The Alameda 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 Alameda County and throughout Alameda County — architectural plans, structural engineering, Title 24 energy compliance, and city submissions. Our 60-day permit guarantee means we manage the entire process.

In Alameda 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 Hayward are choosing detached ADUs for rental income or multi-generational living.

Many older homes in Alameda and Alameda County were built before modern seismic codes. While a roof replacement alone doesn't trigger a seismic retrofit requirement, it's the ideal time to reinforce roof-to-wall connections — especially for homes near the Hayward Fault. Hamilton Exteriors uses Simpson Strong-Tie hurricane clips on every roof we install, which improves earthquake resistance and meets California's latest building standards at no extra cost.

Yes. Parts of Alameda and the East Bay Hills fall within Cal Fire's Very High Fire Hazard Severity Zones (VHFHSZ). Homes in these zones must use Class A fire-rated roofing materials — which includes the asphalt, metal, and tile options Hamilton Exteriors installs. If your property is in a designated fire zone, we also ensure compliant ember-resistant vents and remove combustible material within 5 feet of the roofline as part of our standard installation process.