
California structural & civil engineers specializing in attached ADUs, delivering code-compliant structural and civil engineering plans for ADU structures connected to primary residences. Typical turnaround for structural & civil plan sets is 2-3 weeks. Unlimited plan-check revisions within our engineering scope(1) at no extra cost.
Build your attached ADU with confidence. We engineer ADU additions connected to your existing home—shared-wall connections, foundation tie-ins, load-path design, seismic interaction, and wind exposure—delivering permit-ready PE-stamped plans tailored to your property conditions.
Serving all 58 California counties with expert Attached ADU structural engineering.
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.
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An attached ADU is an accessory dwelling unit that shares at least one wall or structural element with the primary residence. Unlike detached ADUs, attached units are physically connected to the main house, which requires structural analysis of the connection and load transfer between structures. Attached ADUs are often created through additions, garage conversions, or by converting existing space. California building codes require PE-stamped structural plans for all attached ADU projects.
Attached ADU structural & civil engineering costs vary based on project size, complexity, site conditions, and the extent of structural connection to the primary residence. Our pricing includes structural calculations, foundation connection design, shared wall analysis, framing plans, lateral system design, civil engineering coordination, and PE-stamped permit-ready structural & civil engineering plans. We provide same-day quotes with transparent, fixed pricing--no hidden fees or surprises. Contact us for a free quote specific to your attached ADU project.
Yes, California requires PE-stamped structural plans for all attached ADU projects. Structural engineering is mandatory for foundation connections, shared wall design, load transfer analysis, framing systems, lateral force-resisting systems, and seismic safety compliance with California building codes. Attached ADUs require structural analysis of both the new ADU structure and its connection to the existing primary residence.
Typical turnaround for structural & civil plan sets for attached ADU projects is 2-3 weeks. This includes site evaluation (if needed), structural evaluation of the existing primary residence, structural calculations, foundation connection design, shared wall analysis, framing plans, lateral system design, civil engineering coordination, and complete plan sets. Rush services available for urgent projects.
Attached ADUs require structural analysis of the connection between the new ADU and the existing primary residence. Key considerations include load transfer through shared walls, foundation connections, seismic interaction between structures, and ensuring the existing structure can accommodate the additional loads. We provide structural engineering services including shared wall structural design, foundation connection design, load path analysis, lateral force-resisting system design, and structural evaluation of the existing primary residence where connections are made.
Under California ADU law, attached ADUs can be up to 850 square feet, or 150% of the existing primary residence's living area up to 850 square feet, whichever is less. Our structural engineering services accommodate attached ADUs within these size parameters, providing complete structural analysis and design that accounts for the connection to the existing structure.
Attached ADUs may share foundation elements with the primary residence or require new foundation connections. The foundation approach depends on the specific project and existing structure. We provide structural analysis and foundation structural design for attached ADUs, including evaluation of existing foundation capacity, foundation connection design, load-bearing capacity calculations, and foundation type selection based on soil conditions and California building code requirements. Foundation design must account for seismic loads, load transfer between structures, and soil characteristics specific to the project site.
Attached ADU projects may require civil engineering services including site coordination, grading design, and drainage design. We provide high-level civil engineering coordination for attached ADU projects, ensuring proper site layout, drainage considerations, and grading requirements are addressed in coordination with structural design. Civil engineering services are provided at a high level and coordinated with structural plans.
Building departments use various permitting systems--some online, some in-person. We provide complete PE-stamped structural & civil engineering plan sets in PDF format ready for submission. Our plans include all required structural and civil engineering sheets, calculations, and documentation needed for plan check. We also respond to all building department comments throughout the review process.
Yes, we offer construction administration services for attached ADU projects including: responding to contractor RFIs, reviewing shop drawings and submittals, site visits for structural observations, and certification letters. This ensures your attached ADU is built according to structural plans and code requirements.

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Trusted by 3,000+ homeowners and AEC professionals • Licensed in California State • 35+ years experience