Terminology

• Composite deck: deck with embossments that bond to concrete so they act as one slab
• Form deck (non-composite): deck used only as permanent formwork
• Deck depth: rib height; 1-1/2 in., 2 in., and 3 in. common
• Gauge: deck steel thickness; lower gauge is thicker
• Topping: concrete thickness above the top of the deck flutes
• Shear studs: headed studs welded through the deck to the beam for composite beam action
• Pour stop: bent plate at slab edges and openings
• Shoring: temporary support during concrete placement for long deck spans
• Ponding: extra concrete from deck and beam deflection during the pour
• Restrained / unrestrained rating: UL fire classifications based on assembly restraint
• Cellular / electrified deck: deck with cells or trench ducts for wiring

Standards

Ratings

• Deck depths of 1-1/2 in. to 3 in. used with normal-weight or lightweight concrete in UL designs
• Two-hour ratings available with unprotected deck and spray-applied fire protection on beams in common UL designs
• Lightweight concrete reaches a given fire rating with less topping than normal-weight concrete
• Vibration and deflection checked by the structural engineer for open floors

Test standards

• ANSI/SDI C-2017: composite steel floor deck-slabs; ANSI/SDI NC-2017 for non-composite floor deck
• AISC 360: composite beam design
• ASTM A653: galvanized deck steel; ASTM A780 coating repair; AWS D1.3 sheet steel welding
• UL 263 / ASTM E119: fire-resistance designs (UL D-series floor-ceiling designs)

Materials

• Galvanized composite deck: most common; coating weight per specification
• Phosphatized or painted deck: where SFRM adheres better or for interior dry conditions
• Normal-weight concrete: greater mass and stiffness
• Lightweight concrete: reduced dead load and thinner fire-rated slabs
• Reinforcement: welded wire, bars over beams, or fibers for crack control
• Shear studs: headed studs welded through the deck to beams

Detailing

• Coordinate deck direction, span, and shoring with beam layout
• Set slab thickness for fire rating, acoustic needs, and embedded conduit
• Account for ponding in concrete quantity and finish elevation
• Detail pour stops, edge angles, and openings for shafts and MEP
• Specify flatness and finish if the slab is exposed or polished
• Protect galvanized deck that will receive SFRM per the fireproofing manufacturer

Uses

Specific uses

• Office, laboratory, and healthcare floors in steel frames
• Multifamily podium transfer and upper floors in steel buildings
• Mezzanines and platforms
• Roof decks that carry equipment or terraces
• Floors with raised access or electrified deck for wiring

Pros and cons

Pros

• Deck acts as working platform and formwork; no stripping
• Fast to erect with steel frames
• Composite action reduces beam size
• Wide range of fire-rated designs

Cons

• Vibration control needs engineering on long spans
• Deck exposed below needs fireproofing or a rated ceiling in many designs
• Ponding adds concrete and weight
• Floor thickness limits conduit and embedded services

Manufacturing and cost

Construction

• Deck roll-formed from coil; bundles hoisted and spread on beams
• Deck fastened by welds or powder-actuated fasteners; studs welded through
• Reinforcing placed; concrete pumped, screeded, and finished

Main manufacturers and suppliers

• Vulcraft (Nucor)
• Verco Decking
• New Millennium

Trade association: Steel Deck Institute.

Sources

• AISC Modern Steel: new revisions improve UL fire protection design, https://www.aisc.org/modernsteel/news/2016/november/new-revisions-improve-ul-fire-protection-design/
• Steel Deck Institute: standards and publications, https://sdi.org/
• Vulcraft: steel deck products, https://vulcraft.com/
• Hilti: composite deck firestop documentation, https://hilti.com/media-canonical/ASSET_DOC_LOC_16197693_APC_RAW
• Wikimedia Commons: Trapezoidal sheet metal standard roof construction.svg, by 5gon12eder (CC BY-SA 3.0), https://commons.wikimedia.org/wiki/File:Trapezoidal_sheet_metal_standard_roof_construction.svg