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.
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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.
If you are looking for more details, kindly visit steel flooring panels.
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, reach out to Ask ASC Steel Deck.
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 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.
For more information, please contact us using the form below.
Floor pan. Aluminum vs Steel
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by quantumkev » February 18, , 5:36 pm
I am trying to decide whether to use a steel, or aluminum floorpan, and what gauge to use.
If I go with steel I can just weld it on and be done with it. I know corrosion might be an issue using steel, but I am in Texas, so I don't have to worry about that. It will be heavier, but stronger, but if welded on, it is pretty permanent.
If I go Aluminum I have to drill and rivet a LOT of holes.... but it is then at least worst case removable.
Not sure which way to go, and I thought I would open it up for conversation.
What do you think are the pros/cons of each, what experience did you have, and what gauge did you use?
Re: Floor pan. Aluminum vs Steel
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by KB58 » February 18, , 6:52 pm
There have been a lot of threads about this...
Steel, stronger and more puncture resistant, can distort due to welding heat, and can be very heavy.
Aluminum, lighter, probably more expensive (depending upon thickness), easier to puncture, and more of a pain to attach.
Don't forget that unless the likely stitch-welded steel panel is fully sealed, driving through even one puddle is going to get water into the seam and start it rusting from the inside out. A compromise is to either fully seal the seam, or use stainless.
It really comes down to how much you care about total vehicle weight, and how concerned you are that some road debris might someday come up through the floor. I remember driving over one of those 6-ft long breaker bars on the freeway one time. I could only imagine the havoc that would cause if it got bounced up right before the next car drove over it. Too ugly to even think about... Much more likely would be a rock or piece of wood, but still. Remember, for most intents and purposes, what we're building aren't that much safer than motorcycles. You make your choices and take your chances.
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Re: Floor pan. Aluminum vs Steel
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by turbo_bird » February 18, , 8:25 pm
My car has a welded steel floor, I think 16 awg. If I build another, it will be an aluminum floor about .090" thick. That should be just as stiff as the thinner steel floor I have now, as well as lighter. I painted my steel floor, and the paint wears off pretty fast from shoes and grit, I also got a bit too much heat in it when welding it on, so that's a bit annoying. For the next one I would also make the floor pretty much cover the entire bottom of the car with small access holes for oil changes and diff/transmission access. A full under tray would make a small aerodynamic improvement, but a bigger improvement in chassis stiffness. Like KB58 mentioned on safety, I pretty much see it as a four wheeled motorcycle.
Kristian
V6 in a book frame build. Now registered.
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Re: Floor pan. Aluminum vs Steel
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by FieroReinke » February 19, , 12:33 am
I am going welded steel but still debating 16 vs 18 ga. I have sheets of both but still have alot of paneling left to do. I can either do the floor in 16 and the panel behind the seats in 18 or vice versa or buy another panel. I like the weight down low and the protection of the 16 ga floor but that will add more weight.
Build on
Chris
Build: NA Miata based +221 Se7en
Re: Floor pan. Aluminum vs Steel
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by wrightcomputing » February 19, , 7:48 am
I went with an 1/8" Aluminum diamond plate floor. It covers the entire bottom of the car. I think it weights about 55lb, which is heavier duty then most but I like my balls. I got an oil sucker and pull the oil out of the dip stick just like they use on boats.
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Re: Floor pan. Aluminum vs Steel
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by nick47 » February 19, , 9:29 am
I also went welded steel, 16 gauge, and I'm glad I did. Two years and 20K miles and rust hasn't been an issue. What I really like is how stiff and solid the chassis is. Aluminum probably would be as well, but I didn't much like the idea of rivets.
Re: Floor pan. Aluminum vs Steel
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by rx7locost » February 19, , 10:56 am
If (and that's a big
IF) a steel floor is a serious rust issue, how does the frame still not rust if aluminum flooring is used? Steel floor for me and a continuous weld all along the outer edge. Stitch welded along all inside tubes with caulking between the welds to keep out "stuff". Nothing lasts forever. I think 30 years will be enough for me.
If choosing aluminum, consider the next step which is forming the aluminum along the bottom rail/floor and how std rivets may affect that forming and riveting. It is more work to use flush rivets. It is not a problem if a steel floor is chosen and welded along the outer edge of the square tube and ground flush. Either one will work. Success has been had with both materials. Your car, your choice.
Chuck.
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Re: Floor pan. Aluminum vs Steel
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by botbasher » February 19, , 12:45 pm
I decided on the best of both worlds.
I put 12ga stainless on the vert. firewalls and forward floors of the driver & pass compartment. I did 14ga directly under the seat. I'll do the remainder of the car in .040 Alum, but also toying with using .018 stainless and welding it on.
As Wright said... I like the twins where they are and 12ga is bulletproof (.22cal) and I'll trade that weight off for the thin remaining under pan.
Rx7 hit the gorilla in the room though. Alum pan doesn't eliminate a rusting issue. It just moves it from the floor itself to the spaces between!
KS
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Re: Floor pan. Aluminum vs Steel
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by Sam_68 » February 19, , 1:44 pm
rx7locost wrote:If (and that's a big IF) a steel floor is a serious rust issue, how does the frame still not rust if aluminum flooring is used?
Because it's protected by paint/powder coat and an aluminium floor.
The big difference is that whilst an aluminium floor will not be affected by road gravel bouncing up underneath (and completely covers the steel, so protecting it), with steel such inevitable 'road rash' chips off whatever paint or rust-proofing you have applied and lets the rust take hold.
It will also usually be sealed against water ingress by Sikaflex or similar sealant/adhesive between the alloy and the steel (easy to apply a bead before riveting the floor on), whereas, as previously mentioned, a stitch-welded steel floor will trap moisture between the sheet and the tube, unless you take pains to seal it properly afterwards. This is why the sills (rocker panels, I think you guys call them?) are always amongst the first places to rust out on older cars.
Aluminium every time, for me.
Re: Floor pan. Aluminum vs Steel
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by » February 19, , 2:18 pm
absolutely no way you're protecting the internal portions of the frame rails from moisture the second you drill a hole for a rivet. powder coat the rails.. sure.. then drill through it, now you have an exposed hole that will not be 100% sealed by a rivet.
I'll be using steel, with seam sealer between the floor and rails, stitch welded every few finches.
Tucker
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Re: Floor pan. Aluminum vs Steel
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by Sam_68 » February 19, , 3:04 pm
wrote:absolutely no way you're protecting the internal portions of the frame rails from moisture the second you drill a hole for a rivet. powder coat the rails.. sure.. then drill through it, now you have an exposed hole that will not be 100% sealed by a rivet.
As I said above, it is normal practice to use a PU sealant/adhesive (eg. 'Sikaflex' or 'Tiger Seal') between the aluminium and the steel, when riveting.
This gives very effective protection where the tubes are drilled and riveted.
There are thousands of specialist sportscars running round the (salted in winter) roads of this depressingly damp island of mine, that are living testimony to the fact that this approach works.
Re: Floor pan. Aluminum vs Steel
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by horizenjob » February 19, , 3:47 pm
Aluminium every time, for me.
I think it will be more resistant to damage from rocks under the car than steel. At least the reputation for small workboats is that the aluminum will deform a great deal before it actually tears and breaks.
I've always wanted to make a rig to hold a square piece of these materials and drop a pointed weight on it, like a window sash weight. How about a harbor freight anvil mounted on a 2x2 bolted to the basement ceiling joists? You could swing against a target sandbagged against the foundation. What do you folks think would be reasonable?
This is not really trying to represent something pointed but more like a round rock the size of a softball or more that you might go over at 100 KPH.
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Re: Floor pan. Aluminum vs Steel
Post
by turbo_bird » February 19, , 3:52 pm
Sam_68 wrote: wrote:absolutely no way you're protecting the internal portions of the frame rails from moisture the second you drill a hole for a rivet. powder coat the rails.. sure.. then drill through it, now you have an exposed hole that will not be 100% sealed by a rivet.
As I said above, it is normal practice to use a PU sealant/adhesive (eg. 'Sikaflex' or 'Tiger Seal') between the aluminium and the steel, when riveting.
This gives very effective protection where the tubes are drilled and riveted.
There are thousands of specialist sportscars running round the (salted in winter) roads of this depressingly damp island of mine, that are living testimony to the fact that this approach works.
Not to mention that even if you weld a steel floor on to avoid drilling the frame tubes for rivets, you're still going to attach the aluminum side panel with rivets to the same exact tube. At least the holes for attaching the floor are on the bottom of the tube so water will have as much chance of running out again as getting in.
Kristian
V6 in a book frame build. Now registered.
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Re: Floor pan. Aluminum vs Steel
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by Miatav8,MstrASE,A&P,F » February 19, , 5:47 pm
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A sealer between the metals is good but does nothing to keep the water out. The individual rivets are dipped in waxoil (that you can make at home) or other sealant that doesn’t quickly setup.
The sides should wrap the edge of the floor. For an alloy floor, I’d seal, add rivets at the ends, then seal on the sides over the top and use rivets through the floor and the side skin overlap versus flush under the side skin overlap. For steel floor, stitched, painted, then seal the side skin overlap over the floors edge.
Horizon, here is a good article on the various hull materials: https://www.morganscloud.com//08/06 ... o-impacts/
Quote: “Mild steel (until it corrodes) can be somewhat less fracture-prone in impacts than marine aluminum, and is also harder to abrade and easier to repair in the field.”
My reverse trike I’m building is using a .050” steel floor and firewall. My GO4s use aluminum sheet, about .080” thick which I have no intention of replacing with steel. I don’t know the alloy they used and it did corrode, allowing the powder coat to flake off in sheets. I used annealed to modify the floor on the P35 to get more air to the radiator.
Aluminum is a very broad term and all the alloys corrode in one way or another at different rates. Pure aluminum does not, but it isn’t a good structural material. Alclad sheet is an alloy with a thin layer of pure aluminum on top, but it can be scratched through and would be a poor choice for a floor.
In a fire, such as an accident, there is no comparison. Steel will stay solid long after the aluminum is a puddle. Also, in an accident, you do not know if you will be conscious or physically capable of escaping the car. I am not saying everybody should have steel; just sharing some info.
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