Proposed Home Detached ADU

Project Details

This project involves the structural design and engineering of a 500 sq. ft. detached accessory dwelling unit (ADU) designed to sit on a 7,405 sq. ft. residential lot. The layout includes a bedroom, bathroom, and common living area, supported by a foundation system featuring 12″ x 12″ reinforced concrete wall footings and 8″ thick stem walls. The structure is designed with a raised wood deck at the entrance and includes comprehensive utility specifications for electrical, plumbing, and mechanical systems. The design process adhered to rigorous standards, including the 2025 California Residential Code (CRC), 2025 California Building Code (CBC), and ASCE 7-22 provisions. Structural elements utilize Douglas Fir Larch (No. 1 and No. 2 grade) lumber for beams, joists, and rafters, integrated with Structural-I plywood shear walls for lateral load resistance. The assembly is engineered to safely withstand environmental loads, including wind speeds of 94 MPH and requirements for Seismic Design Category D. The foundation is designed for a soil bearing capacity of 1,500 psf, utilizing grade 60 reinforcing steel and specialized Simpson Strong-Tie holdown systems to ensure structural stability.

Role

Structural Engineer/Designer

Services Provided

The scope of services included the preparation of structural analysis, structural calculations, and structural plans for the proposed detached ADU. The structural analysis considered wind, seismic, dead, and live loads in accordance with the California Building Code (CBC) and applicable local Santa Clara amendments. The work included the analysis and design of the structural system, including the foundations, floor framing, roof framing, shear walls, beams, headers, and structural connections, together with the design of the lateral force-resisting system appropriate for a single-story detached ADU. The services also included the preparation of structural drawings consisting of the foundation plan, roof framing plan, shear wall layout plan, required structural sections, and typical structural details, notes, and specifications to support permit review and construction.