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Code Update: New Manual Simplifies Steel Deck on Cold-Formed Steel Framing Design

Thomas Sputo on February 4, 2019 - in Articles, Column

Although cold-formed steel (CFS) trusses and steel deck applications have been available for years, many designers continue to use either plywood deck on CFS trusses or design steel deck applications in the same way they would plywood, without taking full advantage of steel deck’s capabilities.

This lag has been due in large part to a lack of comprehensive, user-friendly information sources on how to implement steel deck on CFS trusses, as opposed to wood deck on CFS trusses or steel deck on open web joists or rolled steel beams. To address this, the Steel Deck Institute (SDI) recently published a comprehensive design manual to help designers unlock the full benefits of steel deck on CFS framing, especially in multifamily environments.

The 241-page manual is an invaluable resource for designers working to SDI standards incorporated into the 2018 International Building Code. It includes applications for steel floor and roof deck and provides design examples, diaphragm tables, fastener properties and useful commentary to simplify the jobs of engineers and architects. It also takes into account common proprietary fasteners and truss chords.

To assist designers with recognizing and accounting for the limit states of steel deck on CFS, the manual includes diaphragm design tables usable in most common applications. With this tool, architects and engineers can take advantage of steel deck’s many advantages over plywood on CFS trusses.

Less Material, Lower Cost

When substituting steel deck for plywood on CFS framing, few designers take full advantage of the ability to double or even triple the distance between trusses. Instead of the maximum two feet on center model for plywood decking, steel deck can support truss separation of four or even six feet on center. In addition, because of steel’s inherent noncombustibility, there’s no need for a fire-resistant concrete or gypsum concrete layer over decking to meet fire code. This reduction in materials cost makes steel deck assemblies highly cost-competitive with plywood decking.

Reduced Cost of Construction

On the jobsite, steel deck on CFS framing is faster to install than plywood. It also can contribute to lower builder’s insurance costs because of dramatically lower fire risk during construction. Both of these factors minimize the construction cost component to total project cost.

Unlike plywood’s standard 4- by 8-feet boards, steel decking comes in a variety of sizes (up to 3- by 40-feet), minimizing the need for onsite labor. Fastener advancements also allow workers to load collated screw packages into screw guns that can be used from a standing position, dramatically reducing installation time and associated labor costs.

Also, steel deck jobsites create virtually no construction waste when compared to the dumpsters full of wood waste from plywood deck applications. Steel products are typically fabricated to precise dimensions, reducing waste on the front end, and what steel scrap may be created has substantial recycling value, compared to the waste removal fees associated with wood waste.

Steel Deck Makes Buildings More Resilient

In addition to the obvious safety benefits of steel over wood related to combustibility, galvanized steel deck on CFS also dramatically reduces maintenance and repair costs in situations such as roof leaks and storm damage. As well as not being subject to rot and reduced strength, even the screw fasteners for steel deck provide more strength in wind uplift situations than the straight nails used by wood.

For architects and engineers looking to take the next step in resilient design, corrugated cold-formed steel wall panels on CFS studs along with steel decking on CFS trusses can form the core of a virtually noncombustible building. These types of applications have been requested more frequently by institutional and educational users, and designers who can expertly take advantage of steel’s capabilities have an advantage in those environments.

Get the Manual

The “Steel Deck on Cold-Formed Steel Framing Design Manual” is available at no cost as a freely distributable PDF download or can be ordered in a print copy for $30 at SDI’s website: www.SDI.org.

Thomas Sputo

About Thomas Sputo

Thomas Sputo, Ph.D., P.E., S.E., SECB, is the technical director of the Steel Deck Institute, a trade organization of steel deck manufacturers. He’s also a consulting structural engineer with Sputo and Lammert Engineering LLC, and an Emeritus Senior Lecturer in the Department of Civil and Coastal Engineering at the University of Florida; email: tsputo50@gmail.com.

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