Metal Deck Dimensions: The Complete Spec & Terminology Reference
If you need metal deck dimensions in one place — depths, coverage widths, gauge thicknesses, coating weights and the vocabulary that goes with them — this is the page to bookmark. At Keystar Industries in Eagan, Minnesota, we field these questions every single day from estimators pricing a bid package, architects filling out a schedule, and contractors trying to confirm what showed up on the jobsite is actually what the drawings called for.
We built this reference the way we wish spec pages were built: tables first, plain English second, no filler. Everything below reflects standard and nominal metal decking dimensions used across the industry. Always confirm final numbers against your manufacturer’s published data and Steel Deck Institute (SDI) load tables before you design or order.
Quick Answer: Standard Metal Deck Dimensions at a Glance
Most metal deck falls into three families — roof deck, composite floor deck, and form deck. Here is the short version.
| Deck Family | Common Profiles | Standard Deck Depth | Typical Coverage Width |
| Roof Deck | Type A, Type B, Type F | 1.5″ | 36″ |
| Roof Deck (long span) | Type N | 3.0″ | ~24″ |
| Roof Deck (short span) | 1″ roof deck | 1.0″ | Varies by manufacturer |
| Composite Floor Deck | 1.5C, 2.0C, 3.0C | 1.5″, 2.0″, 3.0″ | Varies by profile |
| Form Deck (Type-C) | 0.6C, 1.0C, 1.5C | 0.6″ (9/16″), 1.0″ (15/16″), 1.5″ (1-1/2″) | Varies by profile |
That table answers most phone calls. The rest of this guide explains what the numbers mean and where people get tripped up.
Roof Deck Dimensions: Type A, B, F and N
Roof deck is non-composite. It spans between joists or purlins, carries insulation and roofing above it, and acts as a diaphragm to transfer lateral load into the building’s frame.
The 1.5″ Family — Types A, B and F
Here is the detail that surprises people: Type A, Type B and Type F roof deck all share the same 1.5″ deck depth and the same 36″ coverage width. What changes is the rib geometry at the top flange.
| Profile | Common Name | Deck Depth | Coverage Width | Rib Character |
| Type A | Narrow rib | 1.5″ | 36″ | Narrow top flange |
| Type F | Intermediate rib | 1.5″ | 36″ | Mid-width top flange |
| Type B | Wide rib | 1.5″ | 36″ | Wide top flange |
Type B is the workhorse. Its wide top flange gives insulation board more bearing surface, which is why you see it on the overwhelming majority of commercial roofs. Type A’s narrow rib shows up where a thinner rigid board or specific attachment pattern is in play, and Type F sits between the two. Because all three carry the same depth and width, swapping profiles usually does not change your sheet count — but it can change your fastener pattern and your diaphragm values, so check before you substitute.
Type N — 3″ Deep, Long Span
When joist spacing opens up, the 1.5″ family runs out of strength and you move to Type N deck at 3″ deep, typically around 24″ coverage width. The tradeoff is straightforward: deeper deck spans farther, but each sheet covers less width, so you handle more pieces. Deep deck often lets a designer delete a line of joists entirely, and that trade usually pays for itself.
1″ Roof Deck
A 1″ roof deck also exists for short spans and light loads — canopies, small infill areas, tight joist spacing. It is a niche product, not a default.
Browse our full roof deck lineup for profiles we stock and cut to order.
Composite Floor Deck Dimensions
Composite deck is a different animal. It does not just form the concrete — it becomes permanent tensile reinforcement for the finished slab. Embossments rolled into the webs lock the steel and concrete together so the two act as one structural element.
| Composite Profile | Deck Depth | Typical Use |
| 1.5″ Composite | 1.5″ | Shorter spans, common in low- and mid-rise floors |
| 2.0″ Composite | 2.0″ | Moderate spans, thicker slabs |
| 3.0″ Composite | 3.0″ | Longer spans, reduced supporting steel |
Your total slab thickness equals deck depth plus concrete cover over the top of the ribs — a 3″ deck with 3-1/4″ of cover gives you a 6-1/4″ slab. Deeper deck usually means more span and less shoring, but it also means more concrete volume in the flutes. Run the numbers both directions.
See our composite deck options for what we carry in each depth.
Form Deck (Type-C) Dimensions
Form deck is non-composite. It serves as a stay-in-place form for concrete and hands all the structural work off to rebar or mesh in the slab once the pour cures.
| Form Deck Profile | Deck Depth (Decimal) | Deck Depth (Fractional) |
| 0.6 Form Deck | 0.6″ | 9/16″ |
| 1.0 Form Deck | 1.0″ | 15/16″ |
| 1.5 Form Deck | 1.5″ | 1-1/2″ |
You will see both decimal and fractional callouts on drawings for the same product, which causes real confusion on submittals. 0.6C and 9/16″ form deck are the same thing. Same for 1.0C and 15/16″.
Form deck shows up over bar joists, on concrete-topped roofs, and in slab-on-metal-deck assemblies where the concrete is designed independently. Details on our form deck page.
Metal Deck Gauge Chart: Gauge to Thickness
Gauge is the single most misread number in deck ordering. Lower gauge number means thicker, stronger steel. An 18-gauge sheet is meaningfully heavier than a 22-gauge sheet, not lighter.
| Gauge | Nominal Design Thickness (in) | Relative Strength | Common Application |
| 22 ga | ≈ 0.0295″ | Lightest | Short spans, light loads, form deck |
| 20 ga | ≈ 0.0358″ | Light | Common roof deck gauge |
| 18 ga | ≈ 0.0474″ | Medium | Roof and floor deck, longer spans |
| 16 ga | ≈ 0.0598″ | Heavy | Heavier loads, greater spans |
| 14 ga | Thicker than 16 ga | Heaviest common | Heavy loads, demanding diaphragms |
These thicknesses are approximate nominal design values for steel sheet. Verify against your manufacturer’s data before you specify or fabricate, because published design thickness and minimum delivered thickness are not always the same number. The American Iron and Steel Institute publishes the cold-formed steel design standards that govern how these thicknesses get used in calculations.
A practical note from our counter: gauge drives price more than profile does. If a bid looks unusually cheap, check the gauge column first.
Coatings: G60, G90 and Prime-Painted
Deck coating is specified per ASTM A653 for galvanized product. The G-number tells you total zinc weight across both sides combined, per square foot.
| Coating | Zinc Weight (oz/sq ft, both sides) | Typical Environment |
| G60 | ≈ 0.60 oz | Dry, enclosed, conditioned interiors |
| G90 | ≈ 0.90 oz | Exterior exposure, humidity, corrosive conditions |
| Prime Painted | N/A — painted finish | Concealed interior where paint is acceptable |
Rule of thumb we give customers: if the deck will see weather, wash-down, chemical exposure or high humidity, go G90. Parking structures, natatoriums, food processing and exposed canopies are all G90 conversations. Standard dry warehouse or office roof deck is usually G60 or prime-painted. Full coating designations live with ASTM International.
Panel Lengths and Coverage Width vs. Overall Width
Two dimension questions come up constantly.
Panel length. Metal deck is generally cut to order to match the required span and layout — it is not sold in a handful of fixed stock lengths like dimensional lumber. That is exactly how we run it at Keystar: you give us the lengths, we cut USA-made steel deck to your list, and it ships or gets picked up same-day or next-day in most cases.
Coverage width vs. overall sheet width. Coverage width is the usable width each sheet contributes once it is nested and lapped into the sheet beside it. Overall width is the physical edge-to-edge dimension of the flat sheet before installation, and it is always slightly larger. Take off your quantities using coverage width, never overall width — this is the most common cause of short-shipped decking on a job.
Grab our downloadable deck list to keep our profiles and dimensions on your desktop while you take off.
Metal Deck Terminology Glossary
Deck terminology carries over from drawing to submittal to field, and a shared vocabulary prevents expensive mistakes. Here is the metal deck detail language you need.
| Term | Definition |
| Flute | The valley formed between ribs; the low channel that receives concrete or insulation fill. |
| Rib | The raised corrugation running the length of the panel; ribs create the deck’s stiffness. |
| Web | The inclined side wall connecting the top flange to the bottom flange of a rib. |
| Flange | The flat horizontal surface at the top or bottom of a rib. |
| Deck Depth | Vertical distance from the bottom of the deck to the top of the rib (1.5″, 2.0″, 3.0″, etc.). |
| Coverage Width | Usable installed width of a panel after side laps are nested — the number you order by. |
| Overall Sheet Width | Edge-to-edge physical width of the panel before installation; larger than coverage width. |
| Side Lap | The longitudinal joint where one panel’s edge overlaps or nests into the adjacent panel. |
| End Lap | The transverse joint where one panel ends and the next begins, typically over a support. |
| Span (Single/Double/Triple) | The number of supports a panel bears on. Single = 2 supports, double = 3, triple = 4+. Continuity over multiple spans increases capacity. |
| Diaphragm | The deck acting as a horizontal structural plane to carry wind and seismic load to the frame. |
| Embossment | Small ridges rolled into composite deck webs that mechanically bond steel to concrete. |
| Composite | Deck that acts structurally with the cured slab as a single reinforced element. |
| Non-Composite | Deck that carries load only as steel; the slab reinforces itself (form deck, roof deck). |
| Pour Stop | A bent steel edge member that contains wet concrete at slab perimeters and openings. |
| Closure | Sheet metal trim that seals gaps at deck ends, edges, ridges and penetrations. |
| Shoring | Temporary support beneath deck during the pour, used when unshored span capacity is exceeded. |
Closures, pour stops and fasteners all live on our accessories page.
Metal Decking CSI Spec Section (Division 05)
If you are writing or reading a project manual, metal deck sits in CSI MasterFormat Division 05 — Metals.
| CSI Reference | Title | Scope |
| Division 05 | Metals | All structural and miscellaneous metals |
| Section 05 30 00 | Metal Decking | Parent section for all deck types |
| Section 05 31 00 | Steel Decking | Steel roof, composite floor and form deck |
So when someone asks where metal decking in CSI belongs, the answer is 05 30 00, with 05 31 00 Steel Decking nested underneath it. Related work — structural steel framing, steel joists, shear studs — is typically specified in adjacent Division 05 sections, and a good spec cross-references them so nothing falls into the gap between trades.
Important: Dimensions Are Not Load Design
This guide covers dimensions. It does not cover capacity, and the two should never be confused.
Allowable spans and load capacities depend on gauge, profile, number of spans, span length, and the actual loading condition. Two sheets with identical deck depth and coverage width can have very different capacities based on gauge alone. Add snow drift, mechanical units, construction loads or diaphragm demand and the analysis gets more involved.
Use published Steel Deck Institute load tables, manufacturer data, and your project engineer of record for anything structural. We are happy to talk profiles and availability all day — but the span call belongs to your engineer.
Why Contractors Buy Deck From Keystar
We are locally owned and operated out of 1920 Shawnee Road, Eagan, MN 55122, and we supply USA-made steel deck cut to order. Roof deck in Types A, B, C, F and N. Composite deck in 1.5″, 2.0″ and 3.0″. Form deck Type-C in 0.6″, 1.0″ and 1.5″. Plus accessories and equipment rentals.
Most orders ship or are ready for pickup same-day or next-day. When a crew is standing on a roof waiting on material, that matters more than anything on a spec sheet. Take a look at our full product lineup or call us at (651) 256-0008.
Frequently Asked Questions
What is the standard depth of metal roof deck?
The standard depth for Type A, Type B and Type F roof deck is 1.5″, all with 36″ coverage width. Type N deck is 3″ deep with roughly 24″ coverage for longer spans, and a 1″ roof deck is available for short spans and light loads.
What is the difference between coverage width and overall width?
Coverage width is the usable width each panel contributes after side laps are nested with the adjacent sheet. Overall width is the physical edge-to-edge dimension of the sheet before installation and is always slightly larger. Always take off quantities using coverage width.
Is a lower gauge number thicker or thinner steel?
Lower gauge number means thicker steel. 16 gauge (≈0.0598″) is substantially thicker and stronger than 22 gauge (≈0.0295″). 14 gauge is used where loads are heaviest. Verify nominal design thickness with your manufacturer before specifying.
What is the difference between G60 and G90 deck coating?
Both are galvanized coatings per ASTM A653. G60 carries about 0.60 oz of zinc per square foot (both sides combined) and suits dry interior conditions. G90 carries about 0.90 oz per square foot and is used for exterior exposure or corrosive environments. Prime-painted finishes are also available.
What CSI section covers metal decking?
Metal decking is specified under CSI MasterFormat Division 05 (Metals), Section 05 30 00 “Metal Decking,” with Section 05 31 00 “Steel Decking” beneath it.
What lengths does metal deck come in?
Metal deck is typically cut to order to the required span and layout rather than sold in fixed stock lengths. At Keystar we cut USA-made deck to your list and most orders ship or are ready for pickup same-day or next-day.
Get Your Deck Cut to Order
Have a deck list ready, or just a set of drawings and a deadline? Send it over. We will confirm profile, gauge, coating and cut lengths, and get you a number fast.
Request a quote online, contact us with questions, or call (651) 256-0008. You can also visit us at 1920 Shawnee Road in Eagan, MN — and don’t forget to grab the downloadable deck list for your next takeoff.