ADU Builder in Marin County

We serve Northern California across three regions: the San Francisco Bay Area, Greater Sacramento, and the Central Valley. Our published guides cover 14 counties and 88 cities. Our Castro Valley and Sacramento offices support local estimating, permit coordination, and project planning across these regions.

Financing may be available for eligible projects with approved credit. Available terms depend on lender approval, project scope, and current programs. Your project manager can review the options that apply before work begins. We also accept checks, ACH, and major credit cards.

Yes. Hamilton Exteriors holds CSLB License #1078806, active general liability coverage, and the required contractor bond. We also hold GAF Master Elite and James Hardie Elite Preferred credentials. We can provide current proof of coverage before work begins.

Permit requirements depend on the project scope and local jurisdiction. Hamilton Exteriors coordinates required applications, plan documents, corrections, and inspections. Permit fees and allowances appear in the proposal before construction begins.

ADU costs in Marin County vary by city — from Larkspur to San Rafael. With median home values averaging $1,600,000 across the county, we see a range of project scopes. Hamilton Exteriors provides free, itemized estimates for every Marin County project with no hidden fees.

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

In Marin 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 San Rafael are choosing detached ADUs for rental income or multi-generational living.

Marin County communities including Marin often have architectural review or design guidelines that apply to exterior changes — especially in historic districts and hillside zones. Some projects require approval from the Marin County Community Development Agency or local design review boards before permits are issued. Hamilton Exteriors is experienced with Marin's review process and helps homeowners select materials and colors that meet local aesthetic guidelines while achieving their design vision.

Marin's proximity to the coast means higher moisture, salt air exposure, and persistent fog — all of which can shorten the life of standard materials. We recommend James Hardie fiber cement siding for Marin homes because it's engineered for coastal climates and resists moisture, rot, and salt damage for 30+ years. For roofing, we use enhanced underlayment and corrosion-resistant fasteners on every Marin project to account for the marine environment.