Lloyd ADU Structural Design
Project: Lloyd ADU
Architect: Christi Azevedo, Azevedo Design
Firm of Record: JCWagner & Associates, Inc.
My Role: Structural Designer (under supervision of Doug Wagner, PE)
The Vision
Collaborating with architect Christi Azevedo is always a masterclass in efficiency and elegance. For the Lloyd ADU, the objective was to transform industrial materials into a warm, livable space. The design proposed a compact, 20-foot tall auxiliary dwelling capable of sharing a backyard without feeling intrusive. The structural concept utilized a post-and-beam light gauge steel frame combined with insulated metal panels, a system that is efficient to assemble but structurally demanding to detail.
The Challenge: Industrial Materials in Residential Applications
The primary challenge was achieving lateral stability in a structure with a tall, narrow footprint (10' x 20') while utilizing light gauge steel (CFS). Unlike standard wood shear wall construction, this project required a more tailored approach:
Custom Moment Frames: I designed rigid frames using light gauge steel channels rather than heavy red iron to keep the assembly weight manageable for a small crew.
Connection Complexity: The thin-walled nature of light gauge steel meant standard welded moment connections were not an option. I performed a rigorous shear rupture analysis on the bolted moment connections to ensure the steel would not tear under seismic loads.
Hybrid Lateral System: The design integrated steel strap lateral bracing with the moment frames to effectively handle the 16 to 20 foot vertical span.
The Engineering Solution
I delivered a complete calculation package for the superstructure that validated Christi’s slender architectural vision without compromising safety or constructability.
Lateral Analysis: I modeled the custom steel frames to resist wind and seismic forces, paying special attention to the drift (sway) to prevent damage to the insulated metal panel cladding. To maintain the sleek profile and material efficiency, I validated that the insulated metal panels themselves possessed sufficient strength to serve as the structural roof diaphragm.
Gravity Systems: I designed an efficient gravity framing system using cold formed steel members, ensuring they could support the loads of the multi-level living space while integrating seamlessly with the architectural shell.
Feature Stair: The interior features a custom steel spiral staircase. I provided the connection calculations to anchor this "furniture-scale" element securely to the primary structure.
For the completed project photo gallery, visit Christi’s website.