
ADU engineering in San Mateo County is tailored for regional topography, county-level seismic and wildfire risk assumptions, and unincorporated permit-path requirements. San Mateo County ADU structural engineering focused on regional topography, county-wide seismic and wildfire risk criteria, and unincorporated permit pathways.
San Mateo County ADU projects require structural planning for regional terrain variation, county-wide seismic and wildfire criteria, and unincorporated permit pathways. Across San Mateo County, ADU projects are engineered for valley/foothill terrain transitions, jurisdiction-wide hazard conditions, and county plan-check standards in unincorporated areas.
Single-family ADUs are secondary housing units that are located on the same lot as a single-family home. These units are also sometimes referred to as granny flats, in-law suites or backyard cottages.
Share a few project details and our engineering team will review your scope and guide you through permitting and design next steps.
After reviewing your project details, we'll provide a transparent quote the same day--typically within a few hours. Pricing varies based on project scope, complexity, and requirements.
We deliver complete structural permit sets. *If building departments have comments related to our scope, we handle all revisions--no extra fees, no limits.
See why homeowners and industry professionals trust us with their projects.
We engineer all six ADU types in San Mateo: attached, detached, garage conversion, basement, junior (JADU), and multi-family. Each project is designed for your property's specific lot, soil, and code conditions.
Costs depend on project size, complexity, and site conditions. Our fixed-price quotes include:
• Structural calculations and PE-stamped plans
• Foundation and framing design
• Lateral system and seismic engineering
• Civil engineering coordination
Same-day quotes available — no hidden fees. Get a free quote for your San Mateo County project.
Yes — California requires PE-stamped structural plans for every ADU. This covers foundation design, framing, and seismic compliance. This applies whether you're building in South San Francisco, Burlingame, or unincorporated San Mateo County.
Most San Mateo County ADU plan sets are completed in 2–3 weeks — structural calculations, foundation design, framing plans, and civil coordination included. Rush service is available for urgent timelines.
Yes — we design ADU foundations for steep slopes, retaining walls, stepped footings, and hillside load paths throughout San Mateo County. Western San Mateo County communities like San Carlos, Belmont, and parts of Menlo Park include hillside residential areas where ADUs need engineered retaining elements, stepped foundations, and site-specific drainage coordination. Coastal properties in Pacifica and Half Moon Bay face elevated wind loads and marine exposure. We design for both conditions, with every plan addressing the county's position between the San Andreas and Hayward fault systems.
We serve all cities in San Mateo County including South San Francisco, Burlingame, and all unincorporated areas. Each city may have additional requirements, which we address in your plans.
Under California ADU law:
• Detached ADUs: up to 1,200 sq ft
• Attached ADUs: up to 850 sq ft
• Junior ADUs: up to 500 sq ft
Specific limits may vary by city within San Mateo County. We size and engineer your ADU to the maximum allowed on your lot.
Most ADUs don't require additional parking. Parking is typically waived when the ADU is:
• Within 0.5 miles of public transit
• In a historic district
• A conversion of an existing garage
Check with your specific city for local rules.
Yes — garage conversions are one of the most popular ADU types, and you typically don't need replacement parking. Our engineering scope covers slab analysis, wall framing, ceiling structure, and seismic design for San Mateo County garage conversions.
San Mateo County cities generally support electronic plan submittals. The county has been proactive about ADU resources and streamlined review processes. We deliver PE-stamped plans in PDF, ready for submission — all required sheets, calculations, and documentation included. We also handle every plan-check comment through final approval.
Yes. Our construction admin services include:
• Contractor RFI responses
• Submittal review
• Structural site observations
• Certification letters
This ensures your ADU is built to plan and code.

Get a free, no-obligation quote within 24 hours for your ADU structural engineering needs. Our licensed engineers are ready to help with your San Mateo County ADU or JADU project.
Trusted by homeowners throughout San Mateo County • Licensed California PE Engineers • Serving projects across all of San Mateo County