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Case Study:
Steel Architectural Staircase Clad in Stone & Wood
SF Metalworks was selected to fulfill the vision of internationally-recognized interior design firm ODADA in collaboration with general contractor, Cole Brooks.
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Core challenges included providing an internal steel structure driven by numerous constraints: a) Elliptical core frame to be clad in lava stone veneer by an Italian stone fabricator (fabricated separately and simultaneously to the metalwork fabrication). b) Tread frames and landing frames to be clad in wood by a woodworker located in San Francisco. c) Integration with existing house framing & concrete slab. d) Minimal deflection and sufficient strength to support load from stairs in addition to stone cladding. e) Pre fabrication of all steel parts at SF Metalworks. f) Shipping to Hawaii followed by installation.
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Given a site in Hawaii and designers / sub-contractors located in California & Italy, coordination was critical throughout this project. We established a weekly meeting, which allowed the team to keep eachother up to date as the project progressed.
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After months of careful planning, coordination, design, and fabrication, the stair structure was assembled without issue and on schedule.
Technical Highlights:
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We started by developing and refining a schematic design for the stair structure, implementing constraints from the team as required. Upon completion of this design, it was reviewed by a structural engineer. The schematic design phase gave us the opportunity to resolve many design questions and implement changes prior to the construction & shop drawing phase (at which point major changes would have been more time consuming to make). For example, we were able to incorporate a second floor landing structure scope addition with relative ease.
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We then created a highly detailed parametric model from which to produce shop drawings and cut files. This parametric model offered numerous advantages over a more conventional non-parametric approach: 1) Enabled dimensional changes, if required. For example, we could make small changes, like modifying the overall width of the stair, and hundreds of parts would automatically update, dramatically reducing time required for revisions. 2) Given the fact that we had 12 unique stair tread sub-assemblies, we were able to design and detail one tread, then copy and quickly modify the design for the other 11 unique treads. 3) Utilizing digital fabrication, we pre-cut all hole locations, in addition to slots and tabs, allowing all parts and sub-assemblies to self-fixture during assembly. This reduced both shop fabrication time and on-site installation time, in addition to providing laser-cut precision.
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Upon completion and approval of the shop drawings, we exported cut files. These cut files went directly to a laser cutter for flat parts and a tube laser cutter for tube, angle, and channel parts. The parts were assembled and welded into sub-assemblies, and the entire stair structure was then fully assembled in our shop to ensure proper fit and dimensional tolerance.
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The stair was disassembled, spray primed to prevent corrosion, and packed in a shipping container. We constructed a custom wood deck to support two layers of parts and prevent any shifting within the container during transit. The container made its way across the Pacific, where it was unloaded and ready for installation. In order to facilitate an expedient and safe installation, we also fabricated a custom jobsite crane, which was installed within the house.
Stair Structure Numbers:
*Excluding the stone and wood cladding
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Weight: approx. 5,900 lbs
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# of sub-assemblies: 98
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# of unique parts: 409
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Total # of parts: 1,703
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Total # of fasteners: approx. 2,800
