What is steel metal decking?

Updated on: 25/08/2022

Steel decking is also known as metal decking, corrugated steel decking or ‘wrinkly tin’.

With land prices at a premium, particularly in urban areas, it’s common for buildings to be designed and constructed with multiple storeys; from hospitals and office blocks to residential apartment buildings and car parks.

Constructing multi-storey buildings is complex and can be costly. Keeping construction times to a minimum, and therefore reducing labour costs, is one method of reducing the overall cost of a multi-storey construction project.

Sometimes access can also be a problem. Narrow sites hemmed-in between neighbouring high-rise buildings means that traditional methods of construction, such as brick and block, are challenging due to the quantity and weight of the materials and the lack of on-site space for storage and for scaffolding to be erected.

One of the best and easiest ways to minimise construction times whilst ensuring the delivery of a high quality, durable and long-lasting structure in both urban and suburban areas is to build with steel frame and composite steel decking.

What is steel decking?

Steel decking, also known as metal decking, is a sheet of high-performance galvanised steel used in the construction of composite concrete floor slabs. It can also be used as a structural feature in roof construction. When specified as metal roof decking it is used to support insulating membranes.

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.

Steel is also sustainable; it is one of the world’s most recyclable materials with over 40% of ‘new’ steel manufactured from recycled steel.

Companies are finding new ways to make steel ‘greener’. Kingspan, one of the world’s largest providers of steel decking profiles has invested in a low carbon steel manufacturer and intends to source a substantial quantity of the steel used to make their products from this supplier from 2024 onwards.

How is composite metal decking manufactured?

To manufacture metal decking, thin strips of galvanised steel are cold rolled into corrugated, or ribbed, shapes known as profiles.

The two most common steel decking profiles are shallow (dovetail or re-entrant) which are up to 175mm deep and used for short spans, and deep deck (trapezoidal) which are up to 225mm deep and used for longer spans.

Each metal deck profile can be manufactured in a different steel gauge according to construction project requirements, usually between 0.85mm and 1.5mm. Sheet metal gauges are based on a weight of 41.82 pounds per square inch of thickness.

The shape and gauge of the metal deck profile influences factors such as the load capacity, thickness and fire performance of the finished composite floor slab.

sheets of steel decking being manufactured
                                                      Steel floor deck being manufactured

What is a composite concrete floor slab?

Profiled steel decking is commonly used in conjunction with reinforced concrete to create a composite concrete floor slab.

Decking sheets are cut to size and laid horizontally between the beams of a steel structure. The cut end of the deck is sealed off with an end cap and edge trim before each of the sheets is fixed to the top flange of the beam with shear studs using ‘thru-deck ‘or ‘straight to steel’ stud welding techniques.

Sheets of mesh grid reinforcement are laid and fixed over the metal decking and concrete is pumped and screed on top to create a composite concrete floor slab.  Sometimes, the concrete is reinforced with steel fibres rather than mesh. Reinforcement helps with fire performance and crack control.

Indentations in the decking help the metal and concrete to bond and share the load burden.

The shear studs create a composite action between the steel beams and the concrete. Leading multideck manufacturer Kingspan now offers steel decking with Engineered Ends which further improves the overall composite action and performance.

diagram of a composite concrete floor slab on steel decking
                                 A cross section of a composite steel deck concrete floor system.

What is steel decking with Engineered Ends?

Steel decking with ‘Engineered Ends’ is an innovation developed by Kingspan after it was suggested by Raised Floor Solutions, Kingspan’s largest UK metal decking supplier and installer.

Metal decking profiles are manufactured in the usual way but after being cut to size, the end of the metal decking sheet is folded and pressed to form a slope.

The slope allows a greater volume of concrete to come into contact with the steel beams and around the shear studs and fulfils the requirement for full depth concrete.

Engineered Ends also remove the need for galvanised end caps to be manually installed over the end of each decking sheet, reducing labour time and therefore costs which has the advantage of speeding up construction schedules.

Further advantages of steel decking with Engineered Ends include a reduction in the amount of grout lost during the concrete casting process, reducing staining on the steel frame and any paint coatings.

Kingspan steel Decking with Engineered Ends
                                         Composite steel decking with Engineered Ends

Why is steel decking painted?

Steel decking can be ‘painted’ for both aesthetic purposes and to provide additional corrosion protection. The painting process involves a fine powder coating being applied to the deck during manufacture.

If the underside of the deck is to remain exposed, coloured powder coating can help with the interior aesthetics of the building. It can also be used to assist with floor level recognition in multi-storey buildings such as car parks.

When powder coated, galvanised metal decking is equipped with an additional protective layer that helps with corrosion protection. The powder coating enhances the durability of the steel and will not crack, peel, scratch or chip.

For long term corrosion protection in particularly aggressive environments, steel decking can be manufactured with a special Magnelis® coating.

What is Magnelis®?

Magnelis® is an exceptionally tough metallic coating which, when applied to galvanised metal decking, protects it from corrosion even in harsh environments and prolongs its life-span.

Magnelis® is produced on a hot dip production line. The molten bath has a chemical composition of zinc, 3.5% aluminium and 3% magnesium. This unique composition ensures a stable and durable layer across the entire steel decking sheet, including the cut edges, and prevents the profile from coming into contact with the environment.

In tests, Magnelis® provides three times better corrosion protection than standard galvanising. In particularly aggressive environments, such as coastal locations, swimming pools or car parks, the advantage of specifying steel decking with Magnelis® rises to ten times better corrosion protection.

Why is steel decking used for car park construction?

Steel frame and composite steel decking is commonly used for the construction of single storey and multi-storey car park structures because it is quick to erect, low maintenance, long lasting and extremely cost efficient.

Steel is vandal resistant, fire retardant and light, reducing the building’s foundation requirements. It also allows car park designers to satisfy all the elements of good car park design and offers a great deal of design flexibility; rather than the spaces being designed to fit within a fixed structure, the potential unpropped span widths offered by specifying composite steel decking allow the structure to be designed to offer the maximum number of parking spaces, and therefore maximum profit for the car park owner/operator. This is another huge advantage for using steel decking in construction.

Luton Airport MSCP was built using steel frame and composite car park deck with reinforced concrete
London Luton Airport multi-storey car park, for which RFS designed and installed acomposite steel deck concrete floor system

How far can steel decking span?

One of the main advantages of specifying metal decking for the construction of multi-storey structures is that it doesn’t require multiple column supports beneath it to be load bearing.

This is particularly important in the construction of a facility such as a multi-storey car park. Too many columns supporting the upper floors would reduce the number of car parking spaces created, and therefore the profitability of the car park.

How do you buy steel decking?

Raised Floor Solutions is a specialist metal decking supplier and installer and an approved Kingspan contractor. We have been supplying and installing composite metal decking profiles for nearly two decades. Prior to this, we were aligned with a leading steel frame construction business.

Our expert in-house design team is able to advise on the best metal deck solutions for different end user requirements. Using Kingspan software and BIM technology, they can design in-situ composite floor slab solutions for any kind of construction project, including multi-storey car park construction.

The steel decking and metal decking for concrete can be installed on site by our team of highly trained composite flooring contractors.

We also offer steel Slitting coil for  steel decking and composite flooring design services. Simply contact us with your requirements and a member of our team will be in touch.