ADU Builder in Concord

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.

Most ADU contractors in the Bay Area are tradesmen who build from plans someone else designed. Hamilton Exteriors is different. Our founder, Alexander Hamilton Li, is both a licensed architect and a general contractor (CSLB #1078806). This means the person designing your ADU is the same person overseeing its construction. There are no design-to-build handoff gaps, no change orders from unbuildable plans, and every cost itemized when your architect's vision meets your site's reality. Here is what

ADU cost in Concord depends on the building design, site conditions, foundation, utility routes, and finish choices. Heating and cooling equipment also needs to suit the proposed unit. Have the site assessed and the utility work priced before setting the budget. Confirm applicable permit and fire-safety requirements rather than using a standard citywide surcharge.

A 500 square foot detached ADU in Concord typically costs $180,000-$250,000, including design, permits, and construction. Garage conversions of similar size run $150,000 and up. The city's free pre-approved ADU plans can reduce design costs by $10,000-$25,000.

Yes. Concord actively encourages ADU development and offers free pre-approved plans to streamline the process. State law (AB 68, SB 13, AB 881) overrides most local zoning restrictions, including minimum lot size requirements for ADUs under 800 sq ft. Concord cannot require owner-occupancy or replacement parking for ADUs built after January 2020.

Plan on 6-10 months total from design start to move-in. Design and permitting take 2-4 months, and construction runs 8-14 weeks for detached ADUs or 10-14 weeks for garage conversions. Concord's streamlined review process typically approves permits in 4-8 weeks.