Why Is It Better To Use 80 KSI Steel Roof Decking?

Ask The Expert Q&A: Why Use Stronger 80 KSI or Grade E Steel for Roof Decking?

Sentry Roof thinks it should be standard practice to use Grade E steel for roof decking, more recently referred to as 80 KSI, instead of standard Grade C steel for new construction projects. It delivers on two fronts —  it’s a better value and helps your roof perform better.

Joseph Cannon explains why:  

Q: How is steel strength measured?

Steel strength (or quality) is measured in KSI or Kilopounds per Square Inch with one KSI being equal to 1,000 kilos per square inch (you can convert to PSI or Pounds per Square Inch using a KSI calculator). The higher the KSI the stronger the steel. Steel that’s 80 KSI has traditionally been called Grade E steel and steel that’s 33 KSI has been called Grade C steel. Whether you call it by the newer KSI rating name or older grade names, it’s how we refer to the “strength” of the decking that’s being used on a project.

And different strengths have different pullout values, which is critical to commercial roofing.

Q: What is pullout value?

A: Pullout value refers to the energy it takes to pull out a screw from the steel deck measured in pounds. The longer a screw holds tight to the deck — or the more pounds of pressure it takes to remove the screw — the better (higher) the pullout value. When it comes to roofing, steel with a higher pullout value will protect your building better because it can withstand more wind uplift before the attachment fails. And owners prefer that their roofs stay in place no matter what the weather! Manufacturers test all roofing materials to determine the pullout value.


Here you can see steel decking as Sentry Roof crews work at night preparing to install insulation on top of steel decking.


The section we’re working on was at the terminal of Hartsfield-Jackson Atlanta International Airport, which is why we were working at night.

Q: Why is a wider roofing material sheet better for roofing systems?

A: Building owners benefit from using the widest sheets of roofing membrane possible because wider sheets mean fewer seams and fasteners, which are usually the points of failure. For example, if you were using a standard FM I-90 assembly on a normal commercial roofing project with a using Grade C decking you would be required to use 6-foot sheets with fasteners placed at a 12 inches o.c. (on center). If you were to switch to Grade E decking you could use 8-foot sheets with 12 inches o.c. I know that this does not seem like much but it translates to saving 25% on material costs and 10% on labor costs. It also allows the roofing crew to finish their work more quickly, which means a faster turnover to the general contractor.

Q: How much more expensive is higher KSI or grade steel?

A: It’s not! The cost of 80 KSI steel and 33 KSI steel is comparable if not equal. Plus, wider rolls save on transportation and installation costs, and they also reduce the impact on the environment because less energy is used during both of these processes.

Q: Can 80 KSI steel decking be a better value overall for new construction?

A: Absolutely. You can save time and money by using the 80 KSI or Grade E steel. This may seem counter-intuitive but when you consider roofing system in the equation it makes better sense. All testing for your roofing system is done using both Grade C and Grade E roof deck. If you choose to go with Grade E decking you can also use wider TPO or EPDM sheets, which improves roof performance.

Q: Why aren’t more buildings constructed with stronger steel decking if it’s saves time and money?

A: The reasons Grade C is still being used has to do with standard practice and product availability. It takes time for new industry standards to take hold. Architects still design for it and metal deck suppliers still have more of it on hand than stronger steel. At Sentry, we believe it’s only a matter of time before Grade E steel becomes the standard. And we want to be part of that transition because it’s better for our clients.

If you’re involved in new construction, you can talk to your architect about using a stronger steel for your roof deck so you can improve roofing system installation and roof performance over time. If you have any questions about 80 KSI or Grade E steel for roof decking and how it relates to your roof, please feel free to contact me here at Sentry Roof.

Joseph Cannon

Joseph Cannon is Vice President of Estimating and Chief Estimator for Sentry Roof Services. He is responsible for bidding all new construction work and re-roofing projects. He has over 15 years experience in the roofing industry and works with single-plys, metal, shingles, and many other commercial roofing products.  

To contact Joseph, you can call his direct line at (678) 301-5570.

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