R51+ Composite Floor Decking

R51+ is a 52mm deep re-entrant composite floor deck, updated from the original R51 profile in 2018 and now available in both S350 and S450 grade steel. It is the go-to profile for inner-city multi-storey projects where controlling structural zone depth and overall storey height is a primary design consideration.

The re-entrant geometry delivers a virtually flat soffit and achieves a 1-hour fire rating with a minimum slab depth of just 102mm in normal weight concrete. That is among the lowest of any composite steel deck on the market, and it is what makes R51+ the profile of choice when fire performance must be achieved within a tightly constrained floor build-up.

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Key Benefits

52mm deep re-entrant profile, 600mm cover width, virtually flat soffit
102mm minimum slab depth achieves a 1-hour fire rating with normal weight concrete
Available in 0.8mm, 0.9mm, 1.0mm, and 1.2mm gauges in S350 and S450
Optimised profile geometry maximises the structural efficiency of the steel section
150mm trough spacings provide flexibility for shear stud placement
Greater than 85% beam coverage in line with SCI P375, typically removing the need for fire protection to the supporting beam top flange
Soffit wedge nut fixings available with load capacity up to 2kN, the highest in the RMD Profiles floor deck range
Dense concrete section provides excellent acoustic performance, ideal for residential and mixed-use schemes
Acoustic Robust Solution in accordance with Robust Standard Details
TAB-Deck fibre concrete option available as an alternative to fabric mesh reinforcement
CE and UKCA certified, section properties to Eurocode 3

Profile Specification

Profile depth: 52mm
Cover width: 600mm
Trough spacing: 150mm
Available gauges: 0.8mm, 0.9mm, 1.0mm, 1.2mm
Steel grades: S350, S450

Section properties are calculated with supporting testing in accordance with Eurocode 3.

Sectional Properties

Nominal thickness	Design thickness	Grade	kg/m²	kN/m²	Neutral axis	Steel area (mm²/m)	Inertia (cm&sup4;/m)
0.8mm	0.76mm	S350 or S450	12.02	0.118	15.80mm	1,464	56.9
0.9mm	0.86mm	S350 or S450	13.54	0.133	16.20mm	1,657	61.3
1.0mm	0.96mm	S350 or S450	15.01	0.147	16.50mm	1,845	68.7
1.2mm	1.16mm	S350 or S450	17.98	0.176	17.00mm	2,223	85.6

Panel Weight Reference

Approximate weight of a single R51+ sheet at 3 metres length and 600mm cover width (panel area = 1.80 m²). Use these figures for site handling and lifting planning.

Gauge	kg/m²	Approx panel weight (3m sheet)
0.8mm	12.02	~22 kg
0.9mm	13.54	~24 kg
1.0mm	15.01	~27 kg
1.2mm	17.98	~32 kg

Concrete Volume per m²

Normal weight concrete (NWC). Deck and mesh weight not included. Ponding allowance not included. The re-entrant trough displaces less concrete than a trapezoidal profile, so concrete volumes per unit slab depth are higher. This additional concrete mass is what gives re-entrant profiles their acoustic advantage over trapezoidal decks at equivalent slab thicknesses. Source: RMD Profiles Technical Manual.

Slab depth (mm)	Concrete vol (m³/m²)	Wet weight NWC (kN/m²)	Dry weight NWC (kN/m²)
102 (min, 60 min fire)	0.092	2.17	2.12
115 (min, 90 min fire)	0.105	2.47	2.42
120	0.111	2.61	2.56
130 (min, 120 min fire)	0.121	2.85	2.79
140	0.131	3.08	3.02
150	0.141	3.32	3.25
175	0.166	3.91	3.83
200	0.191	4.50	4.40

Fire Performance

The re-entrant profile geometry of R51+ presents a very small soffit opening. This limits heat transfer into the concrete section during a fire, allowing fire ratings to be achieved at significantly shallower slab depths than any trapezoidal profile of comparable depth. Fire design is in accordance with SCI PN005c-GB and BS 5950 Part 8.

Fire rating	Min slab depth, NWC	Min slab depth, LWC
1 hour	102mm	102mm
1.5 hours	115mm	107mm
2 hours	130mm	119mm
3 hours	155mm	139mm
4 hours	175mm	154mm

R51+ provides greater than 85% beam coverage in line with SCI P375. This means no additional fire protection is typically required to the top flange of the supporting steelwork, which can produce meaningful cost savings on schemes with significant beam run lengths.

At 1.5-hour and 2-hour fire periods, mesh sizing requirements increase depending on span and applied load. Contact our team or use the chat assistant to confirm reinforcement requirements for your specific project.

Finishes and Options

Galvanised Z275 — standard coating, suitable for most internal applications
High durability ZM310 — enhanced zinc-magnesium coating for more demanding environments
TAB-Deck fibre concrete — available as an alternative to fabric mesh, simplifying site reinforcement operations

Why Specify R51+?

When storey height is the controlling constraint on a project, R51+ is the profile that unlocks the solution. A 102mm slab achieves a full 1-hour fire rating in normal weight concrete. That figure is not available from any trapezoidal profile in the range. For an inner-city residential tower where every millimetre of floor depth affects the number of storeys that can be delivered within a planning envelope, that difference is commercially significant.

The virtually flat soffit simplifies suspended ceiling installation and gives maximum flexibility for service routing above the ceiling void. The 150mm trough spacing provides good options for shear stud placement, and the re-entrant geometry creates a strong mechanical key into the concrete that performs well in composite beam design.

The 2kN soffit wedge nut capacity is the highest in the RMD Profiles floor deck range and makes R51+ particularly well suited to projects with heavy suspended services or drainage loads from the floor above.

Where acoustic performance is specified to Robust Standard Details, R51+ delivers the dense concrete section that residential developers and housing associations require, without the need to go to a thicker slab to hit the required mass per unit area.

Case Studies

For examples of how R51+ and other RMD Profiles products have been used on live projects, visit our Project page.

View Case Studies

Typical Applications

Inner-city multi-storey residential schemes where storey height is tightly controlled
Student accommodation and build-to-rent developments with acoustic performance requirements
Refurbishment projects where additional floor depth must be kept to a minimum
Mixed-use schemes where a 2-hour fire rating must be achieved from the thinnest practical slab
Any project where acoustic performance and fire resistance from a shallow floor build-up are both design priorities

Compliance and Standards

All RMD Profiles metal decking products are manufactured and supplied in compliance with current UK and European structural codes and best practice guidance:

Designed to Eurocode EN 1993-1-3 for cold-formed steel sections
Compliant with BS 5950 Part 6 for profiled sheeting in structural design
Follows good practice guidance from the Steel Construction Institute (SCI P300)
Supplied in accordance with the BCSA Code of Practice for metal decking and stud welding

Why Choose RMD Profiles?

Since 2009, RMD Profiles has supported thousands of UK contractors, engineers, and developers with dependable roof and floor decking systems. We combine a wide stocked product range with genuine technical expertise, fast-track supply, and a level of service that keeps projects moving.

One of the widest stocked ranges of structural decking in the UK
Exclusive Buy Back Scheme for surplus materials
Certified stud welding and edge trim expertise, in line with BCSA and SCI guidelines
Fast-track supply with 24-hour delivery available (subject to stock)
Trusted partner on over 10,000 UK projects, from hospitals to high-rises

Need span tables or fire design confirmation for R51+?

Our technical team can provide project-specific span and load tables, fire design checks, and layout drawings. Use the chat assistant for an instant initial answer, or contact us directly.

Call 01787 275055 or email sales@rmdp.co.uk

R51+ Composite Floor Deck