Metal Deck 101- Metal Deck Replacement — RoofersCoffeeShop (2022)

September 6, 2019 at 10:00 a.m.

By Michael Polizzi, A.C.T. Metal Deck Supply.

Commercial roofing contractors' experience with replacing metal deck range from often to once in a career.

Either way, most would agree that an open roof is not the best time for a crash course on metal deck! Hopefully this will provide some important tools you’ll need . . . before you need them.

Roofing—A “Now” Business

Our background was in new construction so when getting to know commercial reroofing in the 1990s, we learned something very quickly. When asking the question, “When will you need the deck?”, it was obvious we were often getting the same urgent, almost panicky response of “what do you mean ‘when will we need it?’ Aren’t my guys there yet?” We learned very quickly that roofing is a “Now” business.

Metal deck is provided with the steel package in new construction. It comes into play with reroofing where contractors may have to replace existing decking before installing a new roof. The “urgent” response is often due either to a project coming to a standstill when deck, thought to be fine, turned out to be rusted through all but the paint . . . or from a sudden visit by Mother Nature, resulting in damage from wind, tornadoes and more.

Metal Deck 101- Metal Deck Replacement — RoofersCoffeeShop (1)

A.C.T. Photo—Tornado damage

What is Metal Deck Exactly?

Metal deck is a structural product. It is corrugated steel engineered as part of the structural design of a building. Roof deck will have a roof system above and floor deck is a form for pouring concrete. There are many different types of steel panels. It is helpful to know what metal deck is, by knowing what it is not. In general, metal deck is not:

• An architectural/metal building panel
• Intended to be exposed on the outside of a building
• Produced with a finished paint and warranty
• Produced in galvalume Four key factors for quoting or ordering metal deck are knowing the Type, Gauge, Finish and Quantity required.

1. Type

The most common types of roof deck are:

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B Deck A.C.T. photo—1 1/2” B (Wide Rib)

Metal Deck 101- Metal Deck Replacement — RoofersCoffeeShop (2)

F Deck A.C.T. photo—1 1/2”

Metal Deck 101- Metal Deck Replacement — RoofersCoffeeShop (3)

F (Intermediate Rib) Michael Polizzi A.C.T. Photo—Tornado damage 18 CRCA TODAY /// Spring 2019

A Deck A.C.T. photo—1 1/2” A (Narrow Rib)

Metal Deck 101- Metal Deck Replacement — RoofersCoffeeShop (4)

N Deck A.C.T. photo—3” N (Deep Rib)

Metal Deck 101- Metal Deck Replacement — RoofersCoffeeShop (5)

The primary products specified in new construction are B deck and for longer spans, 3” N deck. F and A decks were common in the past and now mostly used in replacement when matching existing panels. In replacement, roofing contractors are almost always matching existing panels unless the project is a complete tear-off. It is critical to know the exact dimensions of the existing panels. These dimensions include: A.C.T. graphic—deck image of match

• The Depth of the deck
• The Rib to Rib dimension
• The Opening at both the top and bottom of the flute (the low of the profile)

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There are many obsolete profiles that have no exact match. A standard metal deck tip is knowing that F deck will nest into B deck and A deck will nest into both F and B deck.

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A.C.T. graphic—nesting

It is important to note that this will still not solve all cases however, as some of these extinct products having flute openings even tighter than current A deck. A best practice is to take a photo of the existing deck with a tape measure on it and compare it to the dimensions of products currently in production.

Metal Deck 101- Metal Deck Replacement — RoofersCoffeeShop (7)

A.C.T. photo—matching extinct products

Confirming these dimensions prior to having material delivered to your roof will prevent many delays and wasted labor hours.

Concrete Roof Systems

Lightweight concrete roof systems are installed on what are also known as “Form Decks” as they are the same products used to form floors. These decks are typically lower profile and lighter gauge panels installed over steel with closer spans.

Form decks for lightweight concrete roofs:

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A.C.T. Photo 9/16” 1 5/16” 1” 1 1/2”

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Knowing the rib to rib dimension should be especially heeded when trying to match 1” form deck. There are many profiles, both current and obsolete, with dimensions that vary slightly between ribs. Anyone who has ever dealt with matching these knows how quickly this type of panel fall out of sync when even slightly off.

2. Gauge

Roof deck mostly ranges between 22 and 16 gauge and lightweight concrete form deck ranges between 28 to 20 gauge. The lower the number, the thicker the steel. When the type or gauge of the deck is not clear, a very important factor is knowing the joist or steel spacing. In this case, product load tables can be provided to an engineer for specification.

3. Finish

Metal deck is a structural product and most commonly comes in these finishes:

• Prime painted gray
• Prime painted gray on top with a primer white bottom
• Galvanized in a G60 or G90
• .60 oz/per sq. ft. vs. .90 oz/sq. ft. of zinc
• Galvanized plus a factory applied primer
• Stainless Steel
• For food-grade or extremely corrosive environments

For prime painted deck, the Steel Deck Institute (SDI) Roof Deck Design Manual states, “Prime paints by nature are impermanent and provisional. Prime paint alone will only protect the steel for a short period of time under ordinary exterior atmospheric conditions.” Remember, this is not a finished paint.

For galvanized deck, the language has grown more extensive in recent years, but earlier manuals stated, “In corrosive or high moisture environments, a galvanized finish is desirable.” A chalky, white film forms when galvanized deck is exposed too long to moisture. This is a chemical reaction from the zinc’s “self-sacrificial characteristics” protecting the steel (for a full review visit sdi.org.) The steel is structurally sound but in cases without a drop ceiling, it may not be a preferred aesthetic by an owner.

Of course, you want the best possible product for your customers, so it is worth learning the proper handling of these finishes in order to protect your work. Properly handled, metal deck will look great and last a very long time. If left exposed to the elements too long, it will rust and develop rust staining. The SDI Design Manual provides the following regarding site storage “steel deck shall be stored off of the ground with one end elevated to provide drainage and shall be protected from the elements with a waterproof covering, ventilated to avoid condensation.”

4. Quantity Required

Asking for the correct quantity may sound like common sense but how that quantity is communicated can mean all the difference for an accurate and timely quote. Here are some examples that should be helpful:

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• Total square footage needed
• Dimensions of areas to be covered
• Exact cutlist desired
• Square foot budget pricing

Fastening: With What and Where Exactly?

In addition to quoting and ordering information, having a great understanding of fastening is important to the project.

Metal deck can be fastened with welds, screws or shot down with pins. Most commonly used for deck replacement is the self-tapping screw. Welding sparks and pins shot from a tool cause unnecessary risks over an existing structure.

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A.C.T. graphic, fastening patterns 20 CRCA TODAY /// Spring 2019 There are many fastening patterns and they are important to follow as they are part of the structural design of the building. This pattern is what tells the installer exactly where to fasten the deck both to the supporting steel and at the sidelaps, between the span. Breaking down, the common code of “36/4 w/1” is:

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A.C.T. graphic - fastening pattern 36/4w/1

• 36 = The width in inches of one panel (panel widths vary.)
• /4 = Four fastening points “per” 36” panel on the steel support.
• w/1 = “With” one sidelap screw per span. There are other metal deck products, accessories and rare finishes available that you may inquire about as needed. In the meantime, a great foundation is to remember above all:
• F fits into B and A fits into both F & B
• Type, Gauge, Finish & Quantity
• Know your dimensions!

When the answer is so often, “I need it now!”, hopefully this has you well prepared with the tools you’ll need . . . Before you need them. Michael Polizzi is the Sales Manager for A.C.T. Metal Deck Supply. This CRCA Associate Member firm is a metal deck distributor with 15 locations in 11 states headquartered in Aurora, IL. For more information, call 800.894.7741 or visit metaldecksupply.com to view the Metal Deck 101 video series.

About A.C.T. Metal Deck Supply

A.C.T. Metal Deck Supply is a full-service metal deck distributor with 15 locations in 11 states serving the U.S. and abroad. Metal roof deck, form deck and composite floor decks are available in all types, gauges, and finishes for immediate use as well as any size order produced for any project requirements and schedule. Specialty products: stainless steel, cellular and acoustic decks, construction drawings, take-off and project management are also available.

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For more information, visit www.metaldecksupply.com or 800-894-7741.

Original article source: CRCA Today Spring 2019 issue

FAQs

What is Type B metal deck? ›

Type B Deck is the most common structural metal decking in the industry. It is an ideal structural substrate on short to medium span conditions that range from three feet to ten feet in distance. B Deck is lightweight, strong, economical, and easy to install. The panel in the image below is 1.5” deep and 36” wide.

What is the standard size of steel deck? ›

Deck lengths can be varied to suit the job conditions, but because of shipping considerations, are usually less than 40′ long. Standard deck with varies with the product used, but full sheets are usually 12″, 18″, 24″, 30″, 32″ or 36″. Deck is typically furnished in a standard width with the ends square cut.

What are the different types of steel decking? ›

Four types of steel decking are commonly installed in the non-residential steel construction industry throughout the world. These are roof deck, deck form, composite deck, and deck specialty.

Is metal deck a flexible diaphragm? ›

A metal roof deck diaphragm is a fairly flexible system somewhat analogous to a truss as shown in Figure 2. Prior to installing the truss diagonal or attaching the diaphragm to the supports (and each adjacent sheet via sidelap connectors), neither of the frames possess much strength or stiffness.

What is the strongest type of steel deck? ›

W3-36 is the strongest metal floor deck. It's available as light as 22 gauge and as heavy as 16 gauge.

What is Type C decking? ›

Type C deck provides the platform that supports concrete slabs for constructing floor systems. Use stay-in-place form deck to provide an economical support for structural concrete in floor construction. Also, use Type C decking (9/16”, 15/16”, and 1-1/2”) with lightweight insulating fill for floor or roof applications.

How far can metal deck span? ›

Based on a standard profile of about 2 in. to 3 in. composite deck, typical spans are 10 ft to 15 ft. “When you use a dove- tail profile, you can span 15 ft., but you have to shore it,” notes Abbata.

What is the thickness of steel deck? ›

This is because there is a wide range of steel thickness. In general, steel sheet metal can range from 7 gauge to 30 gauge. However, the range of gauges that metal deck is manufactured in is a smaller range.
...
What Is A Metal Deck Gauge?
GaugeThickness in Inches
20.0359
18.0478
16.0598
3 more rows
May 8, 2020

How far can you cantilever a steel deck? ›

A maximum cantilever length of 450mm (from toe of beam) can be safely installed when the deck spans perpendicular to the support. For cantilevers greater than 450mm, suitable edge protection positioned outside of the slab edge position should be provided to allow safe installation.

What is the advantage of steel deck? ›

Composite metal decking is perfect for use in both floor and roof construction because it has a high strength-to-weight ratio. Other advantages of metal deck include uniform quality, proven durability including excellent fire performance and cost efficiency.

What does metal decking look like? ›

Metal decking typically has a ribbed or corrugated profile that is achieved through a process called roll forming. Large sheets of metal are pulled off of rolls and led through rolling dies that create the ribbed profile. Metal decking is used for flooring and roofing and also for the creation of forms for concrete.

What steel metal deck is? ›

What is Steel Decking? Also called metal decking, steel decking is a structural panel made of corrugated metal sheeting that's used as a structural roof deck or composite floor deck.

Is a steel deck a rigid diaphragm? ›

1.2 the only diaphragm condition that is permitted to be considered Rigid is diaphragms of concrete slabs or concrete-filled metal deck with diaphragm span-to-depth ratios of 3 or less in structures that have no horizontal irregularities. All other diaphragms, according to Section 12.3.

What is a steel deck diaphragm? ›

Design of Steel Deck Diaphragms - YouTube

What is a flexible diaphragm? ›

A diaphragm is considered flexible, when the midpoint displacement, under lateral load, exceeds twice the average displacement of the end supports. It is assumed here that the relative stiffness of these non-yielding end supports is very great compared to that of the diaphragm.

What does E stand for in steel? ›

Category 1
Application symbolMeaningMechanical Property
EEngineering steelsMinimum Yield Strength
BSteel for reinforced concreteCharacteristic Yield Case
RSteel for rail useMinimum Yield Case
HHigh Tensile Strength Flat productsMinimum Yield Case
6 more rows

Is steel decking structural? ›

What is Steel Decking? Metal deck is a key Structural Building Component in steel construction. Metal Deck is made by rolling steel coil to corrugated rolled to a specified geometry. Thus, deck is made by cold forming structural grade steel coils into a pattern of flutes and ribs into various shapes.

Why is metal decking corrugated? ›

Corrugated metal is a lightweight building material that provides remarkable rigidity given its slim profile. That strength makes it an ideal addition to concrete floors in need of extra reinforcement.

What is the difference between steel form decking and composite floor deck? ›

Steel form deck and composite floor deck are both used to support wet concrete and are similar in many ways, but there is one distinctive difference. Steel form decking does not increase the strength of the floor. Composite floor deck will increase the strength of the floor system.

What is non composite metal decking? ›

Non-Composite Metal Roof Deck isn't intended for concrete. It is a smooth panel, with no embossment pattern. It is a structural roof deck that provides both diaphragm shear and vertical load capacity. As with the Composite Floor Deck, there are different profile types that each provide different diaphragm strength.

What is non composite steel deck? ›

Table of Contents. Also known as form deck, A stay in place steel deck that is used to form structural concrete without the use of embossments.

What does B deck mean? ›

B-Deck is a widely used panel for decking. Type B-Deck is frequently used for several applications such as flooring, siding, and roofing. MPI stocks 22 ga. galvanized panels in 20' and 25' lengths.

How much does metal deck weigh? ›

B roof deck can be manufactured in the following gauges: 22, 20, 18, & 16. 22 Gauge is the lightest, weighing 1.9 pounds per square foot. 16 gauge is the heaviest, weighing 3.5 pounds per square foot.
...
B Deck Gauges.
GaugeWeight Per Square Foot
221.78 to 1.90
202.14 to 2.30
182.82 to 2.90
163.5 to 3.54
Mar 27, 2020

How do you waterproof under a deck? ›

Installing a deck drainage system during construction is the best way to waterproof under your entire deck. A deck drainage system diverts water away from the joists and beams. An over-the-joist deck drainage system such as Trex RainEscape provides 100% protection from the damage caused by wood repeatedly getting wet.

What gauge is metal decking? ›

Metal decking is most commonly 16, 18, 20, and 22 Gauge in thickness.

What is the minimum gauge thickness for a steel deck roof? ›

Homeowners choose 29 because: Since it's the minimum thickness for a metal roof, it's usually the least expensive. 29-gauge panels are usually more than adequate for residential homes.

What does B deck mean? ›

B-Deck is a widely used panel for decking. Type B-Deck is frequently used for several applications such as flooring, siding, and roofing. MPI stocks 22 ga. galvanized panels in 20' and 25' lengths.

What is Type A roof deck? ›

Type A Roof Deck is 1.5" deep. Also known as narrow rib, this structural metal roof deck provides a wide support surface for various types of rigid insulation and roofing materials.

What is F deck? ›

F Deck is an original standard and provides an economical choice for roof deck application. CSM Metal Deck stocks and manufactures type F roof deck in 22, 20, 18, and 16 gauge. F Deck is typically recommended for roof deck repairs or re-roofing projects, and is most cost-effective for small roofs, canopies, or awnings.

How much does B deck weigh? ›

B roof deck can be manufactured in the following gauges: 22, 20, 18, & 16. 22 Gauge is the lightest, weighing 1.9 pounds per square foot. 16 gauge is the heaviest, weighing 3.5 pounds per square foot.
...
B Deck Gauges.
GaugeWeight Per Square Foot
182.82 to 2.90
163.5 to 3.54
2 more rows
Mar 27, 2020

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