Bay Area Custom Home Builder. One Team From Design to Move-In

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.

Yes. Hamilton Exteriors builds custom homes throughout Walnut Creek — including Northgate, Rossmoor, Saranap, Parkmead, Lakewood, and Indian Valley — as well as neighboring San Ramon, Danville, Lafayette, and Orinda. Walnut Creek's 1950s–60s California ranch lots are a strong match for tear-down-and-rebuild projects, and the Mt. Diablo foothills offer some of the Bay Area's best hillside custom home sites. See our <a href="/service-areas/contra-costa-county-ca/walnut-creek-ca/custom-homes">Walnut Creek custom home page</a> for local permit timelines, Indian Valley hillside considerations, and recent projects. Typical Walnut Creek custom home budgets run $1.5M to $4M for 3,000–5,000 sq ft builds on existing lots.

Bay Area custom home construction costs $350 to $800 per square foot depending on finishes, site conditions, and architectural complexity. A 2,500 sq ft custom home typically costs $900,000 to $2,000,000 including design, engineering, permits, and construction. Lot preparation, grading, and utility connections add $50,000 to $200,000 depending on the site — hillside lots with difficult access or poor soil conditions tend toward the higher end. Permit fees in Bay Area cities range from $30,000 to $80,000 for new construction, including plan check, school impact fees, and utility connection charges. Hamilton Exteriors provides detailed, itemized estimates at every stage of design and construction, with a guaranteed maximum price at contract signing so there are no surprises during the build.

Custom home construction in the Bay Area takes 12 to 18 months from permit approval. The design and permitting phase adds 4 to 8 months depending on architectural complexity and local plan review timelines — San Francisco and some Peninsula cities have longer review cycles than East Bay jurisdictions. Total timeline from initial consultation to move-in is typically 18 to 24 months. The foundation and framing phases together account for roughly 4 to 6 months of construction, with mechanical rough-in, drywall, and finishes completing the remaining timeline. Your dedicated project manager provides weekly progress updates, real-time schedule tracking, and coordinates all subcontractor sequencing to prevent the scheduling gaps that commonly cause delays on custom home projects.

Design-build means one company handles architecture, engineering, permitting, and construction under a single contract. This eliminates the coordination gaps between separate architects, engineers, and builders that cause delays and cost overruns — the most common source of budget surprises on custom home projects. Hamilton Exteriors' in-house architect designs your home while our construction team provides real-time cost feedback, so the design stays within budget from day one. Every material and system choice is priced during design, not after. The result is a guaranteed maximum price before construction begins, with a single point of accountability from concept through move-in. Design-build typically saves 10 to 15% compared to the traditional architect-then-bid approach because it eliminates redesign cycles when bids come in over budget.

California law requires a licensed architect or engineer to design residential structures over two stories or exceeding certain size thresholds. Even for single-story custom homes, detailed architectural plans with structural engineering are required for building permits in every Bay Area jurisdiction. Hiring a separate architect typically costs 8 to 15% of construction cost and adds months of back-and-forth before construction can begin. Hamilton Exteriors' founder Alexander Hamilton Li is a licensed architect and general contractor (CSLB #1078806), so design and construction are handled in-house under one contract — no separate architect needed. This means design decisions account for construction feasibility and cost from the start, eliminating the expensive redesign cycles that commonly happen when architects and builders work separately.

Yes, but hillside construction requires specialized engineering for foundations, retaining walls, drainage, and seismic bracing. Bay Area hillside lots in the Oakland Hills, Marin headlands, and Los Gatos mountains often require geotechnical reports, soil testing, and engineered pier-and-grade-beam foundations rather than standard slab-on-grade. Retaining walls for hillside sites typically cost $200 to $500 per linear foot depending on height and soil conditions. Many hillside lots also fall within Wildland-Urban Interface fire zones, requiring Chapter 7A compliant exterior materials and defensible space planning. Access for construction equipment is another key factor — narrow hillside roads may require specialized delivery logistics that add to the project timeline. Hamilton Exteriors has experience with hillside construction across Alameda, Contra Costa, and Marin counties and coordinates all geotechnical and civil engineering as part of our design-build process.

Yes. Many Bay Area homeowners tear down aging homes to build new on existing lots, especially in established neighborhoods with desirable locations. This avoids the cost of land acquisition. Zoning determines maximum building envelope, setbacks, and height. Some jurisdictions offer streamlined permitting for rebuild projects on previously developed lots. Hamilton Exteriors evaluates your lot for buildability during the free consultation.

Custom homes are designed from scratch for a specific homeowner and lot. You control every decision from floor plan to finishes. Spec homes are built by developers to sell on the open market, with standard layouts and finishes chosen for broad appeal. Custom homes cost more per square foot but deliver exactly what you want. Hamilton Exteriors builds custom only — every project starts with your vision and your lot.

Yes. Hamilton Exteriors specializes in architect-led luxury custom homes across Alameda, Contra Costa, Marin, and Santa Clara counties, including hillside lots in the Oakland Hills, Berkeley Hills, Los Gatos Mountains, and Marin headlands. Luxury builds from $600 per square foot include custom millwork, chef kitchens, primary suites with spa baths, wine rooms, smart home systems, and indoor-outdoor living designed for Bay Area climate. Hillside luxury homes require engineered pier-and-grade-beam foundations, reinforced retaining walls, and Chapter 7A fire-resistant exteriors in WUI zones. Every luxury project is designed in-house by our licensed architect so structural, aesthetic, and cost decisions stay aligned from day one.