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Metal Deck 101 Everything Roofers Need to Know W Michael Polizzi & Nicholas Camardo Roofing companies do not rise and fall on membranes alone. The structural substrate matters. During the educational seminar, Michael Polizzi and Nicholas Camardo of A.C.T. Metal Deck Supply delivered a practical session for contractors who find themselves dealing with metal deck on reroofs and repairs. This blog turns their presentation into a fast, usable field guide. It explains what a metal deck is, how to identify profiles, how to order it without surprises, and how to avoid the jobsite pitfalls that lead to callbacks. If you want every detail, including profile diagrams, fastening tables, and real job photos, watch the full session video: https://www.youtube.com/watch?v=4h3K4lKSVog Why Metal Deck Should Be on Every Roofer’s Radar Metal deck is a structural product. It is designed to span supports and carry loads. It is not an architectural panel and it is not meant to be a finished exterior surface. Roof systems sit on top of metal deck, and floors use deck with concrete. Roofers usually meet deck during reroofing, where rust, storm damage, or code upgrades force section replacement. Key structural supports you will see: Steel beams, bar joists, or purlins Increasingly, metal studs paired with lightweight concrete on low-profile deck The Four Specs You Must Get Right When you request pricing or place an order, your supplier will need: Type (profile and depth) Gauge (sheet thickness) Finish (galvanized or prime painted, other coatings) Quantity (pieces and lengths, not just square footage) Get these wrong, and budgets, schedules, and warranties can go sideways. Profiles You Will See Most: A, F, B, and N B-Deck Depth 1.5 inches, 36 inches wide, flutes at 6 inches on center Most common in new construction and long joist spacing Often called “wide rib” F-Deck and A-Deck Also 1.5 inches deep, narrower rib openings Used today mostly to match existing profiles in reroofs Helpful nesting rules: A fits into F and B. F fits into B. Always verify dimensions N-Deck Depth 3 inches, typically 24 inches wide, flutes at 8 inches on center Easy to spot, used to span longer distances FIELD TIP! Bring a tape. Photograph the opening at the top and bottom of the flute with a tape in the frame. Older era decks vary slightly. Small differences block nesting and create expensive rework. Matching Obsolete Profiles Without Guesswork Legacy decks from the 1960s and 1970s still show up. Some had interlocking sidelaps, especially in seismic regions, which can prevent a simple overlay. A clean workflow: Measure depth, flute spacing, overall width Capture top and bottom flute openings with a tape in-frame photo Confirm if overlay is feasible or if remove and replace is the safer choice Remember that overlays add weight and can trap moisture, which accelerates corrosion Gauges That Count for Roof Deck Roof deck typically starts at 22 gauge 22 to 18 gauge are most common for reroof work 16 gauge exists for heavy duty spans Low-profile light-gauge decks are common under lightweight concrete systems Deeper profiles and heavier gauges allow longer spans. Always coordinate with the engineer of record. Finishes and Corrosion Protection Galvanized: G60 is common inland. G90 is common in coastal or corrosive environments Prime painted white bottom brightens interiors in warehouses Factory-applied paint over galvanizing improves field paint adhesion Stainless steel deck can be the right answer for harsh or FDA environments. The upfront cost can be lower than repeated replacements About white rust Galvanized surfaces can show a powdery film after trapped moisture. Structural capacity is usually unaffected, but exposed ceilings may need cosmetic remediation. Handling and Storage: Protect Your Reputation Metal deck edges are cut steel. If bundles sit wet, staining can appear. Protect yourself: Store off the ground, tilted for drainage, covered with a waterproof cover, and ventilated so moisture can escape Do not shrink-wrap bundles airtight Ship only what you need if schedules are in flux For exposed ceilings, ask the supplier to pull cleaner sheets for highlight areas Ordering Without Surprises You buy pieces, not only square footage. Communicate scope in one of four ways: Total square footage that must be covered Count and size of openings to infill Budgetary square-foot price for bid placeholders Exact takeoff list of piece counts and cut lengths Freight is a big swing factor. Three sheets cost almost the same to deliver as many more. Plan orders to limit partial deliveries. Specialty Decks You Will Encounter Long-span profiles. 3 inches, 4.5 inches, 6 inches, 7.5 inches, spanning 20 to 30 feet Acoustic deck. Perforated flutes with sound batts. Common in schools and auditoriums Cellular deck. Bottom plate for stiffness and clean ceilings Dovetail deck. Accepts sliding nuts for MEP hangers without penetrations Orientation affects insulation spanning. Coordinate early with the design team. Concrete Over Deck: Form vs Composite Form deck for lightweight concrete roofs. Shallow profiles, many similar variants. Matching existing requires precise measurements Vented form deck can help moisture move through certain mixes Composite deck for floors has embossments that lock concrete and steel. Roofers still see it on mixed-use retrofits Accessories That Save the Day Fasteners. Self-tapping screws to supports, sidelap stitch screws Welds. Rare on reroofs and risky for interiors Pins. Powder-actuated or pneumatic where specified Rubber closures for open cells at eaves or facades Insulation batts for acoustic flutes Weld washers for thin sheet Sump pans for drains Fastening patterns are structural. They should be set by the engineer of record or by approved design tables. Fastening Patterns Without the Jargon How to read a common note like 364 W1: 36. Sheet width in inches 4. Four fasteners across the sheet W1. One sidelap fastener across the span Examples: Inch-and-a-half decks have flutes at 6 inches on center. “4” means every other flute N-deck is 24 inches wide. “244” means every flute gets a fastener Sidelap fasteners are often required when spans exceed about 5 feet A button punch tool may be needed on older interlocking sidelaps. Steel Strength: 40 ksi or 80 ksi Steel Deck Institute minimum is often 40 ksi Some warranties or specs require 80 ksi This must be coordinated early. Requiring 80 ksi after fabrication begins leads to delays and change orders In partial reroofs, mixing new 80 ksi with unknown existing steel does not create an 80 ksi warranted assembly Submittals and Specs You Will Actually Use Data sheets and load tables cover most requests Check Division 05 and Division 07 for galvanizing, coating, and fastening notes Some jurisdictions treat roof installation as acceptance of deck attachment. Walk the deck, verify attachment, and document before you proceed What Metal Deck Is Not Not standing seam roofing Not R-panel or 7.2 exposed fastener panels Not a finished architectural panel with a paint warranty Metal deck is a structural substrate. Tolerances allow minor strap marks or handling dings Final Takeaways from the Session Treat metal deck as structural. Choose profiles and fastening accordingly Identify the existing profile before you order. Measure, photograph, and verify flute openings Select finish by environment. G90 for coastal, stainless for severe exposure Protect bundles and plan deliveries. Moisture and poor storage create headaches Coordinate early on 80 ksi and fastening patterns with the engineer of record Credit: This summary is based on an RCAT educational session presented by experts from A.C.T. Metal Deck Supply. Keep learning with RCAT Learn about RCAT Licensing and why it matters: https://www.rcat.net/licensing.html Find a vetted contractor by ZIP and license type: https://web.rcat.net/rcat/search
Roofing companies do not rise and fall on membranes alone. The structural substrate matters. During the educational seminar, Michael Polizzi and Nicholas Camardo of A.C.T. Metal Deck Supply delivered a practical session for contractors who find themselves dealing with metal deck on reroofs and repairs.
This blog turns their presentation into a fast, usable field guide. It explains what a metal deck is, how to identify profiles, how to order it without surprises, and how to avoid the jobsite pitfalls that lead to callbacks.
If you want every detail, including profile diagrams, fastening tables, and real job photos, watch the full session video: https://www.youtube.com/watch?v=4h3K4lKSVog
Metal deck is a structural product. It is designed to span supports and carry loads. It is not an architectural panel and it is not meant to be a finished exterior surface.
Roof systems sit on top of metal deck, and floors use deck with concrete. Roofers usually meet deck during reroofing, where rust, storm damage, or code upgrades force section replacement.
Key structural supports you will see:
When you request pricing or place an order, your supplier will need:
Get these wrong, and budgets, schedules, and warranties can go sideways.
Bring a tape. Photograph the opening at the top and bottom of the flute with a tape in the frame. Older era decks vary slightly. Small differences block nesting and create expensive rework.
Matching Obsolete Profiles Without Guesswork
Legacy decks from the 1960s and 1970s still show up.
Some had interlocking sidelaps, especially in seismic regions, which can prevent a simple overlay. A clean workflow:
Deeper profiles and heavier gauges allow longer spans. Always coordinate with the engineer of record.
About white rust Galvanized surfaces can show a powdery film after trapped moisture. Structural capacity is usually unaffected, but exposed ceilings may need cosmetic remediation.
Metal deck edges are cut steel. If bundles sit wet, staining can appear. Protect yourself:
You buy pieces, not only square footage. Communicate scope in one of four ways:
Freight is a big swing factor. Three sheets cost almost the same to deliver as many more. Plan orders to limit partial deliveries.
Orientation affects insulation spanning. Coordinate early with the design team.
Fastening patterns are structural. They should be set by the engineer of record or by approved design tables.
How to read a common note like 364 W1:
Examples:
A button punch tool may be needed on older interlocking sidelaps.
Credit:
This summary is based on an RCAT educational session presented by experts from A.C.T. Metal Deck Supply.
Keep learning with RCAT
Learn about RCAT Licensing and why it matters: https://www.rcat.net/licensing.html
Find a vetted contractor by ZIP and license type: https://web.rcat.net/rcat/search