McClure Earns 2025 CFSEI Design Excellence Award for Curved CFS Assemblies in California Residence

Featured image: A worker installs cold-formed steel (CFS) assemblies in a California, residence. Profile courtesy of CFSEI. Photos courtesy of Radius Track. Details courtesy of McClure.

A striking double-curved façade sets apart the Rancho Monte Alegre residence in Carpinteria, California. Custom cold-formed steel (CFS) tabbed box assemblies support the modernist exterior, blending seamlessly with the home’s wood framing.

Specialty engineering firm McClure designed the exterior, double curved CFS custom fabricated tabbed box assemblies. McClure won First Place — Residential/Hospitality in the 2025 CFSEI Design Excellence Awards. The Cold-Formed Steel Engineers Institute (CFSEI) presented the awards. Lauren Gutknecht of McClure submitted the entry.

Cold-formed steel (CFS) tabbed box assemblies support the modernist exterior of a California home — and a CFSEI Award for McClure.

Details show McClure’s cold-formed steel (CFS) tabbed box assembly design.

Custom CFS Tabbed Box Assemblies

The design called for a complex, curved façade that wraps around both the interior and exterior, creating continuously varying surfaces. The initial proposal involved laser-cut plywood grids, but that approach proved unfeasible. A custom CFS solution emerged to handle the doubly curved geometry.

The most unusual challenge was that the interior and exterior planes of the walls diverged, causing the CFS studs to vary in depth along their height. Additionally, the wall finishes were not perpendicular to one another. So the CFS box assemblies — formed from individual flat plates to make the webs and flanges — took on parallelogram shapes and not standard rectangular cross-sections. This geometry allowed them to accommodate doubly curved surfaces.

CFS Laser-Cut from Sheet Steel

To achieve the required curvature, custom-fabricated tabbed box assemblies were laser-cut from flat sheet steel. The engineers designed each piece with pre-punched tabs and holes, allowing them to be riveted together. This method effectively created self-jigging assemblies: as the tabs were connected to matching holes, the shape naturally formed the intended arc.

The team conducted an extensive engineering evaluation. They verified the components could handle shear, axial loads, torsional demands and biaxial bending moments. The analysis included finite element modeling, rational structural design checks and careful application of American Iron and Steel Institute (AISI) specifications for CFS — even though these unique shapes were not addressed by standard design guides.

The team accommodated this complex design by transferring the stud model from Rhino to RISA for structural analysis. The team post-processed the force results in Excel using the RSG CFS plugin to allow for custom shape analysis and AISI code checks.

The exterior double curved, cold-formed steel (CFS) tabbed box assemblies support the two-story residential structure.

The design called for a curved facade that wraps around the interior and exterior, creating varying surfaces.

Structural Movement and Load Transfer

The doubly curved surfaces necessitated complex movement joints that transferred gravity loads at the mid-level floor. The ceiling, soffit and lower walls suspended from below, while the upper walls slipped at the roof. This sequencing of load transfer was critical. It avoided unsightly expansion joints that would have compromised the architect’s vision. Through careful coordination, the design team enabled the entire assembly to accommodate structural movement while maintaining the façade’s uninterrupted, curvilinear appearance.

CFS Accommodates Gravity Loads

Originally conceived as a non-bearing wall system, the CFS assemblies also had to accommodate unexpected gravity loads near the stair framing. The cramped area around the stair core left no room for separate support columns or beams. Engineers reconfigured the CFS assemblies to include a narrower, straight box beam placed between the principal steel columns. This modification enabled the framing to carry the necessary stair loads without altering the overall geometry.

The interior and exterior planes of the walls diverge, causing the cold-formed steel (CFS) studs to vary in depth along their height.

McClure detailed cold-formed steel (CFS) tabbed box assemblies.

Pushing CFS Boundaries

Rancho Monte Alegre exemplifies how CFS can be adapted. Cold-formed steel tabbed box assemblies support the modernist exterior, serving both the architectural ambition and rigorous structural demands. The project is unique — from the laser-cut tabbed boxes accommodating doubly curved walls to the careful integration of movement joints and load-bearing modifications. The project demonstrates an approach to shaping metal that extends beyond standard CFS design practices. The result is a modernist, curved structure that blends structural precision with a unique architectural form.

Read the complete story about the cold-formed steel (CFS) non-bearing panels and obtain the complete design diagrams for McClure’s 2025 CFSEI Design Excellence — First Place — Residential/Hospitality here.

Doubly curved surfaces necessitated complex movement joints that transferred gravity loads at the mid-level floor.

Additional Resources

• eBook: Specifying Cold-Formed Steel Framing: A Guide for Architects and Engineers
• Insights and Inspiration Take Center Stage at 2025 CFSEI Expo in Raleigh
• SFIA Reveals 7 Winners of the 2023 Industry Project Awards in Online Ceremony
• McClure wins CFSEI Award for Balcony Design at Titletown Residential Project Near Green Bay