Best Builders in San Francisco, CA

SFBayADU is a one-stop shop for Bay Area ADUs, specializing in homes from 600 to 1200 sq ft.

Acton ADU is a Bay Area design-build firm with 35+ years of construction experience, offering fully managed ADU projects from feasibility through final warranty. Headquartered in Campbell, they serve 40+ Bay Area cities including San Francisco. All units are traditionally site-built to California residential standards — the company explicitly does not use prefab or modular construction. San Francisco poses some of the most complex ADU permitting environments in California, with layered historic preservation requirements, tight lot constraints, and lengthy approval timelines. Acton ADU's permitting expertise and established relationships with city departments make them a strong fit for SF homeowners who don't want to navigate that process alone. They offer both pre-designed Build Ready plans and fully custom ADUs. ADU costs in San Francisco typically run higher than elsewhere in the Bay Area — $400–$650 per square foot is common, with total project budgets of $300K–$500K+ for detached units. Full project timelines including SF permitting can stretch 12–18 months. Financing guidance and curated interior packages are included in their service offering. Consistently strong customer reviews point to clear communication, professional project management, and deep knowledge of California ADU regulations. Best suited for SF homeowners willing to invest in a high-quality, fully managed build.