Proposed ADU Conversion
Project Details
This project involves the structural design and engineering for a 427 sq. ft. proposed ADU conversion of an existing garage. The comprehensive scope required structural solutions for the entire assembly, including 2×6 DF No. 2 roof rafters spaced at 24″ O.C., a 6-3/4″ x 12″ glulam ridge beam, 2×12 DF No. 2 floor joists @ 16″ O.C., and 6×12 DF No. 1 floor beams. The primary structure utilizes Douglas Fir-Larch lumber integrated with Structural I plywood sheathing and modern timber connectors to ensure a durable residential assembly. The design process included a rigorous structural analysis—utilizing specialized software such as ForteWeb and Tedds—to verify that all members could safely withstand gravity and environmental loads. The structural elements were engineered in accordance with the International Building Code (IBC 2021), the 2022 California Building Code (CBC), 2022 California Residential Code (CRC), and ASCE 7-16 provisions. Special attention was given to lateral load resistance through the use of wood structural panel shear walls with Simpson Strong-Tie hold-downs (HDU2 and HDU5), providing stability against wind speeds of 92 MPH and the stringent requirements for Seismic Design Category E. The foundation system leverages the existing reinforced concrete slab on grade and strip footings designed to perform reliably under an allowable soil bearing pressure of 1,500 psf.
Role
Structural Engineer/Designer
Services Provided
The scope of services includes the preparation of comprehensive structural calculations and structural drawings for the proposed structure. Structural calculations shall include complete loading analyses for wind, seismic, dead, and live loads in accordance with the applicable building codes and project site conditions. The work shall encompass the analysis and design of all structural components, including foundations, columns, beams, shear walls, bearing walls, roof diaphragms, floor diaphragms, floor joists, headers, ridge beams, rafters, connectors, and other related structural elements necessary to establish a continuous and code-compliant load path. The calculations will verify that all structural members and systems are capable of safely supporting and transferring gravity and lateral loads from the roof and floor systems down to the foundation.
The services shall also include the preparation of a complete set of structural drawings for permitting, coordination, and construction. The drawing set shall include a Foundation Plan identifying the layout and sizing of foundation elements; a Second Floor Framing Plan showing the framing arrangement and structural member sizes; and a Roof Framing Plan indicating rafters, beams, and diaphragm components. The drawings will also include Ground Floor and Second Floor Shear Wall Layout Plans defining the lateral force-resisting system, a Structural Section to illustrate vertical load paths and framing relationships, and typical structural details, notes, and specifications required to clearly communicate the design intent and construction requirements. All documents shall be prepared to support efficient plan review and accurate field implementation while ensuring compliance with applicable codes and engineering standards.