ADU Builder for San Mateo and the Bay Area Peninsula

Looking for an ADU builder in San Mateo or on the Peninsula? CALIBUILDER builds custom accessory dwelling units from approved plans — with structured estimating, permit coordination, and project management through final inspection.

CALIBUILDER Construction Inc. · CSLB License #999089

1660 S Amphlett Blvd Ste 103, San Mateo, CA 94402

info@calibuilder.com · (650) 822-1121

What we build

• Detached backyard ADUs

• Attached ADUs

• Garage conversions and Junior ADUs (when your plans and city rules allow)

• ADUs paired with additions or remodels on the same property

We primarily build from client-provided architectural and engineering plans. If you are early in the process, we can collaborate in pre-construction and connect you with trusted design professionals.

How estimating works

1. We review your plans in detail.

2. We perform quantity takeoffs by trade.

   1. You receive a structured proposal with scope of work, assumptions, allowances, and cost breakdowns.

      1. We raise RFIs when clarification is needed before final pricing.

      2. ADU costs in the Bay Area vary with size, design, site conditions, utility connections, structural requirements, permitting, and finish selections. We provide project-specific estimates once plans are available.

   2. Permits and inspections

   3. As the general contractor, we coordinate permitting, inspections, and compliance with local city requirements, including construction management, waste management, and site logistics.

3. Cities we serve

4. Based in San Mateo. We serve San Mateo County, Santa Clara County, and the greater Bay Area — including San Mateo, Burlingame, Hillsborough, Millbrae, Atherton, Menlo Park, Redwood City, Palo Alto, Mountain View, Los Altos, Sunnyvale, Cupertino, Saratoga, Los Gatos, San Jose, and surrounding communities.

Why homeowners pick CALIBUILDER

• 70+ completed Bay Area projects

• Hands-on construction with a strong engineering and architectural background

Over 25 years of combined team experience

• Clear scopes, organized estimates, and updates with photos and shared docs

FAQ

Do I need plans before contacting you?

No. Final pricing needs a complete plan set, but we can review conceptual designs and give early budgeting guidance.

How long does an ADU take?

Timelines depend on scope, permitting, and complexity. ADUs may take several months. We provide a detailed schedule once scope is defined.

Get started

Have plans ready? Send them for a structured estimate. Still early? Schedule a call we’ll map next steps.