Accessory Dwelling Unit & Residential Addition

Project Details

This project involves the comprehensive renovation and expansion of an existing single-family residence, featuring a porch conversion into living space, a kitchen addition, and the construction of a new two-story addition. The two-story structure houses two independent Accessory Dwelling Units (ADUs), with one unit located on the first floor (474 sq. ft.) and a second unit on the upper floor (480 sq. ft.), complemented by new deck assemblies totaling 104 sq. ft. The structural design utilizes Type V-B wood-frame construction engineered to meet the requirements of the 2025 California Building Code (CBC) and 2025 California Residential Code (CRC). The primary framing consists of Douglas Fir Larch beams and joists supported by a reinforced concrete foundation system utilizing 4,000 psi compressive strength concrete. For lateral stability, the design incorporates wood shear walls and specialized hardware, such as Simpson Strong-Tie hold-downs, to resist seismic and wind loads. Rigorous structural analysis was performed to ensure the assembly can withstand environmental conditions specific to the region, including a design wind speed of 96 MPH and Seismic Design Category D requirements (SDS = 1.144). The foundation features independent reinforced concrete footings and a slab-on-grade system designed for a soil bearing capacity of 1,500 psf. Additional project scope includes a 400 Amp electrical panel upgrade, installation of high-efficiency mechanical systems, and site improvements such as new concrete walkways and drought-tolerant landscaping.

Role

Structural Engineer/Designer

Services Provided

The scope of services included the preparation of structural analysis, structural calculations, and structural plans for the proposed structure. The structural analysis considered wind, seismic, dead, and live loads and included the analysis and design of all primary structural components, including roof rafters and roof diaphragm sheathing, shear walls, floor joists and subfloor diaphragm sheathing, load-bearing walls, beams, columns, connectors, lintel beams, headers, and wall and pad footings. The services also included the preparation of structural drawings consisting of the foundation plan, first and second floor framing plans, roof framing plan, first and second floor shear wall layout plans, required structural sections, and typical structural and construction details, notes, and specifications to support permit review and construction.