Proposed House Extension and Accessory Dwelling Unit (ADU)
Project Details
This project involves the structural design and engineering of a residential house extension and an Accessory Dwelling Unit (ADU) located at 1448 12th Ave. The comprehensive scope required engineering solutions for the entire structural assembly, including floor and roof framing systems (joists, rafters, and beams), all supported by a specifically designed reinforced concrete foundation. The primary structure utilizes Douglas Fir Larch (No. 1 and No. 2) lumber framing integrated with Structural-I plywood sheathing and wood shear walls to ensure a lightweight yet durable assembly. The design process included a rigorous structural analysis to ensure the extension could safely withstand environmental loads in accordance with the 2022 California Building Code (CBC), ASCE 7-16, and ACI 318-19. Special attention was given to lateral load resistance through the use of wood structural panel shear walls and Simpson Strong-Tie hold-down connectors, providing stability against wind speeds of 92 MPH and requirements for Seismic Design Category D. The foundation system features independent reinforced concrete wall and column footings designed with a minimum compressive strength of 4,000 psi to perform reliably under a soil bearing capacity of 1,500 psf.
Role
Structural Engineer/Designer
Services Provided
The scope of services included the preparation of complete structural calculations and structural drawings for the proposed structure in accordance with the applicable governing building codes and project requirements. Structural calculations included loading analyses for wind, seismic, dead, and live loads to establish the design forces acting on the structure. The work encompassed the structural analysis and design of all major structural components. This included the design of roof rafters and associated subfloor or roof diaphragm sheathings; shear walls including stud sizes and spacing, wall sheathings, and nailing requirements; and load-bearing walls with appropriate stud sizing and spacing. The scope also covered beam supports required for large open spaces, which may have consisted of wood or steel beams depending on structural loading demands. In addition, the design included concrete slab-on-grade systems, continuous wall footings supporting shear walls and load-bearing walls, and pad footings for columns supporting beams. All calculations ensured a continuous and code-compliant load path capable of safely resisting gravity and lateral loads. Structural drawings included a coordinated set of plans and supporting details necessary for permitting and construction. The drawing package consisted of a Foundation Plan identifying the layout of footings, slab-on-grade elements, and supporting foundations; Floor Framing Plans illustrating the arrangement and sizing of framing members; and Roof Framing Plans indicating the configuration of rafters and related structural components. Shear Wall Layout Plans were provided to identify the location and extent of the lateral force-resisting system. The drawings also included Structural Building Section Views, consisting of both cross-sectional and longitudinal sections, to clearly illustrate vertical load paths and the relationships between structural elements throughout the building. The drawing set was supplemented with typical structural details, typical construction details, general structural notes, and technical specifications required to clearly communicate the design intent and ensure proper implementation during construction.