Comprehensive FAQs About Steel Decking: Everything You Need to Know
What is Steel Decking?
Steel decking is cold-formed steel panels installed on support framing in a roof or floor, including steel roof deck, non-composite steel floor deck, and composite steel floor deck. Steel decking may also be referred to as metal deck, decking or just deck.
Steel deck is a structural building component that transfers vertical and lateral loads through the building. Some of the definitions below were extracted directly from the Steel Deck Institute.
What are Steel Deck Components?
Steel decking is offered in different profiles, but all consist of key components: Top flange, bottom flange, web, and sidelap.
Figure 1. Steel Deck Components
Figure 2. Steel Deck Sidelap Options
The top and bottom flanges are the horizontal elements of the steel deck. The webs are the vertical elements of the steel deck, tilted at a specific angle. Steel deck panels are connected to each other at the sidelap. Steel deck profiles are typically offered with a variety of sidelap options to support: screw connections, power actuated connections, welded connections and other proprietary connections.
Floor deck profiles typically have two additional components: Embossments, and stiffeners. Although embossments are a necessary component of floor deck profiles, stiffeners may or may not be an element and vary depending on profile and manufacturer.
Figure 3. Steel Floor Deck Components
Embossments are regularly spaced indentations, or lugs, on the various surfaces of a steel deck profile for the purpose of achieving composite action between the profiles sheet and the cured structural concrete. Composite action refers to a frictional bond between the steel deck and concrete that increases the strength of the total system. Stiffeners are formed grooves, bead projections or depressions usually parallel to the longitudinal axis of the steel deck used to strengthen the flat element against local buckling or to minimize oil canning.
What are the Different Types of Steel Deck?
Roof Deck – Steel deck panels used in a structural manner as a base for constructing and supporting the roof insulation and membrane.
Composite Floor Deck – A specific steel deck profile used as a form to create a structural concrete slab with the steel deck as moment reinforcement. The steel deck has embossments, interlocking profile geometry, or other
horizontal shear resistance devices to develop mechanical bond between the steel deck and concrete so the slab compositely resists vertical and diaphragm shear loads. Prior to composite action, the steel deck acts as form deck or work platform.
Composite floor deck embossments may vary in shape, size and pattern depending on profile and manufacturer.
Figure 4. Embossment Pattern Example
Non-Composite Floor Deck – Steel deck used as a stay-in-place form for structural concrete. This decking may be designed to resist superimposed loads in a non-composite manner and may also be referred to as Form Deck.
Acoustic Deck – Steel deck panels that have a series of perforated webs and/or flanges which are backed by sound absorbing elements for the purpose of decreasing the sound level within a room by reducing reverberation.
Perforations may vary in shape, size and pattern depending on profile and manufacturer. The sound absorption is tested, measured, and reported by a Noise Reduction Coefficient (NRC). The higher the NRC value, the higher the sound absorption.
Figure 5. Acoustic Deck Variations
Cellular Deck – Steel deck panels comprised of a profiled panel (sometimes referred to as the hat or beam) and factory-assembled with a flat steel sheet on its underside (sometimes referred to as the plate or pan). Alternatively, it may also be comprised of two profiled panels factory-assembled with one panel in the normal position and one panel inverted on the underside. In either case, the assembled panels contain longitudinal cells or cavities intended for acoustical elements or utility raceways.
Beams are traditionally attached to the pan through welding, which can result in weld and burn marks that require treatment in the field to achieve a smooth finish. ASC Steel Deck offers Smooth Series, an advanced cellular deck solution in which the beam is attached through riveting, a process that avoids unsightly weld marks.
Cellular deck may also be offered with a perforated plate (or pan) making it a cellular acoustic steel deck panel. These panels have their own NRC values and can be used in both roof and floor applications.
Figure 6. Cellular Deck Variations
Perforations may vary in shape, size and pattern depending on profile and manufacturer. The sound absorption is tested, measured, and reported by a Noise Reduction Coefficient (NRC). The higher the NRC value, the higher the sound absorption.
What is Steel Deck Used For?
Steel deck is primarily used to support overlying roofing materials or to serve as a permanent form and/or positive reinforcement for concrete floor slabs. Steel deck is a structural component of the building and carries both vertical and lateral loads depending on the application.
Steel deck is used in most commercial buildings such as warehouses, schools, hospitals, airports, office buildings, data centers, stadiums, etc. Steel deck is a non-combustible material making it a desirable building product for both Type I (Fire-Resistive) and Type II (Non-Combustible) construction.
How Does Steel Deck Perform Structurally?
Steel deck is used to resist construction loads and service loads. Construction loads are loads applied to the temporary or permanent structure during construction. Service loads are loads applied to the structure when used as designed and under which serviceability limit states are evaluated.
Steel deck resists out-of-plane loads. These are loads that are applied perpendicular to the surface of the panel and can be applied in inward and outward direction. Inward out-of-plane uniform loads are typically a combination of gravity loads and inward wind loading conditions. Outward out-of-plane uniform loads are typically wind uplift loads.
Steel deck also resists in-plane diaphragm loads. These loads are due to either wind or seismic loads and run parallel to the surface of the panel.
How to Specify Steel Deck?
Steel deck is specified by type (roof, floor, etc.), profile family (B, N, 2W, 3W, etc.), gage (thickness), sidelap (screwable, welded, proprietary, etc.), finish (galvanized, prime painted, etc.) and other characteristics (cellular, acoustic, etc.) when applicable.
If you need assistance specifying steel decking, please reach out to ASC Steel Deck’s Technical Representative.
What are the Benefits of Steel Deck?
Steel deck has structural strength, is fire-resistant, and can be constructed in various weather conditions. Steel deck is an engineered product with uniform product quality and proven durability. Steel deck is an economical choice of building material compared to other materials. Steel deck can be used in exposed applications due to its clean appearance. Steel deck can offer acoustical properties and is a sustainable choice.
What are the Different ASC Steel Deck Profile Families?
ASC Steel Deck offers a wide range of steel deck products, including roof, composite, non-composite, acoustic, cellular, cellular acoustic, galvanized, and factory primer painted with various sidelap options and thicknesses. Learn more by downloading our Roof Deck Catalog and Floor Deck Catalog.
What are Proprietary ASC Steel Deck Products?
ASC Steel Deck has a few proprietary products supported by third-party verification reports.
DeltaGrip® – DeltaGrip is a pneumatic sidelap attachment system that reduces the install costs of high-shear diaphragms by eliminating the costly sidelap seam welds and the need for sidelap screws. Learn more about our DeltaGrip sidelap connection tool HERE.
Smooth Series – Smooth Series is an architecturally exposed riveted cellular deck that provides clean beam (hat)-to-pan (plate) connections by replacing traditional spot welded attachments with aesthetically pleasing riveted attachments. Learn more about our Smooth Series product HERE.
Prime Shield® – Prime Shield is a prime painted cold-rolled ASTM 1008 steel deck. The standard gray primer paint is applied to both the top and underside of the steel roof deck and to the bottom side only for composite floor deck profiles. This gray primer paint is suitable for use in many UL fire-rated assemblies. Learn more about our Prime Shield product HERE.
