Quick answer
Steel Deck Flooring is profiled (ribbed) steel sheet used to form the floors and roofs of a building. There are two main types: composite floor decking, which acts as permanent formwork and then as tension reinforcement in a concrete slab, and roof deck, which forms the structural deck of a roof. It installs fast, creates a safe working platform, and works with the concrete to make a strong, lightweight floor.
Steel decking is one of the most widely used systems in modern construction, but if you are new to it, the terms can be confusing. Metal deck, steel deck, composite floor deck, roof decking: they all describe the same family of profiled steel products. This guide explains what steel decking is, how it works, the benefits, the main types, and where it is used.
What is steel decking?
Steel decking is a profiled steel sheet, rolled into a corrugated or trapezoidal shape that gives it strength and stiffness, then fixed across a supporting steel frame. That profile is what lets a thin sheet of steel span between beams and carry load. It comes in two broad families:
- Composite floor deck, which forms concrete floor slabs.
- Roof deck, which forms the structural deck of a roof.
Both are supplied in a range of profile depths and steel gauges to suit the span and load, from shallow profiles for short spans up to deep long-span profiles for large industrial buildings.
What is Floor Decking?
Floor Decking, also called composite floor deck, is the profiled steel sheet used to form a concrete floor. The decking does two jobs. During construction, it acts as permanent formwork and a safe working platform, so there is no need to strike shuttering afterwards. Once the concrete has cured, the deck acts as tension reinforcement, working together with the concrete as a composite slab.
That composite action is the whole point. Because the steel and concrete share the load, the slab can be thinner and lighter than a traditional reinforced concrete floor, which reduces the load on the frame and foundations and speeds up the build.
Roof deck vs floor decking
| Composite floor deck | Roof deck | |
|---|---|---|
| What it does | Forms a concrete floor slab, working with the concrete as a composite | Forms the structural deck of a roof, carrying insulation, membrane and loads |
| Acts as | Formwork, working platform, then tension reinforcement | Structural deck and load path back to the frame |
| Typical use | Multi-storey floors, mezzanines, extensions | Industrial, commercial and warehouse roofs |
The benefits of steel decking
- Durable. Made from high-strength galvanised steel, both roof and floor decking stands up to the demands of a construction site and lasts the life of the building.
- Fast to install, lower labour. Wide, lightweight sheets cover ground quickly and fix down without specialist kit, which shortens the programme and cuts labour cost.
- Structural strength. On a floor, the deck reinforces the slab and adds to the structural integrity of the building through composite action.
- Versatile. Steel decking suits everything from high-rise floors and industrial roofs to mezzanines, extensions and small works.
- Clean concrete finish. The flat, even soffit helps deliver a good-quality slab with less surface preparation.
- A safe working platform. Once laid, the deck gives site teams a safe surface to work from, with a typical construction load of around 1.5 kN/m² carried by the bare steel alone before the pour.
- Fire resistant. Steel decking is non-combustible, and composite slabs achieve the fire ratings required across construction classifications.
Types of roof decking
Roof decking is supplied in a range of profiles to match the span, load and build-up. The main ranges are:
- Roof deck: TATA RoofDek (D32S through to D200) and Firths SR profiles, from shallow to deep long-span.
- Composite floor deck: TATA ComFlor, MetFloor and Firths floor profiles, in re-entrant and trapezoidal forms.
See the full range on our roof products and floor products pages, or ask us which profile suits your span and load.
Where is decking used?
Steel decking is used across commercial, industrial and residential construction: multi-storey office and residential floors, warehouse and factory roofs, retail and distribution buildings, mezzanine floors, and smaller projects such as extensions, garden rooms and refurbishments. Wherever a strong, fast, lightweight floor or roof decking is needed, our profiles fit the bill.
Frequently asked questions
What is steel decking?
Steel decking is a profiled steel sheet used to form the floors and roofs of a building. It is rolled into a ribbed profile for strength, then fixed across the supporting steel frame. The two main types are composite floor deck and roof deck.
What is steel deck flooring?
Steel deck flooring, or composite floor deck, is the profiled steel used to form a concrete floor slab. It acts as permanent formwork and a working platform during construction, then as tension reinforcement once the concrete cures, so the steel and concrete work together as a composite slab.
Is steel decking structural?
Yes. Composite floor deck reinforces the concrete slab and contributes to its strength through composite action, and roof deck forms a structural deck that carries load back to the frame. Both are designed to the relevant Eurocode standards.
What is the difference between roof deck and floor deck?
Roof deck forms the structural deck of a roof and carries insulation, membrane and loads. Floor deck (steel deck flooring) forms a concrete floor slab and works compositely with the concrete. They use different profiles designed for their job.
Is steel decking fire resistant?
Steel decking is non-combustible, and composite floor slabs are designed to meet the fire ratings required by the building classification, so it adds to the fire safety of the structure.
How much load can decking take during construction?
Typical composite floor deck carries a construction load of around 1.5 kN/m² on the bare steel before the concrete is poured, giving site teams a safe platform to work from. Always check the load table for the specific profile and span.
Talk to the decking experts
RMD Profiles supplies the full range of profiles across the UK, with layout drawings, calculations and technical support from design through to delivery.