ComFlor® 225

Developed specifically for Corus Slimdek® system, ComFlor® 225 offers up to 6.5 metres unpropped span. ComFlor 225

Corus Slimdek® engineered flooring solution is a unique structural floor system which uses Asymmetric Slimdek Beams, where the bottom flange is wider than the top flange. The ComFlor® 225 steel deck bears on the lower flange of the beam which results in a minimal overall floor depth. The concrete that surrounds the beam provides composite action without the need for shear studs and fire protection to the beam. The Slimdek® system is fast, eliminates temporary props, is structurally optimized and saves on cladding costs.

The system also reduces building height or enables extra floors to be built.

  • ComFlor® 225 deck is a state of the art cold formed profile design offering fully optimized composite and load carrying characteristics.
  • The re-entrant section to the top flange of the profile enhances composite action and offers easy services attachment.
  • The deck is designed to offer flexible service integration (as described in Steel Construction Institute publication ‘Service Integration in Slimdek®’).
  • Up to 2 hours fire rating with unprotected soffit.
ComFlor® 225 composite slab – volume and weight
Weight of concrete (kN/m2)
Normal weight concrete Lightweight concrete
Slab depth (mm) Concrete volume (m3/m2) Wet Dry Wet Dry
285 0.116 2.74 2.68 2.17 2.05
290 0.121 2.85 2.79 2.26 2.14
295 0.126 2.97 2.91 2.35 2.23
300 0.131 3.09 3.02 2.45 2.32
305 0.136 3.21 3.14 2.54 2.41
310 0.141 3.32 3.26 2.63 2.49
320 0.151 3.56 3.49 2.82 2.67
350 0.181 4.27 4.18 3.38 3.20
380 0.211 4.97 4.87 3.94 3.73
400 0.231 5.44 5.33 4.31 4.08


Volume & weight table notes

1. Deck and beam deflection (i.e. ponding is not allowed for in the table).
2. Deck and mesh weight is not included in the weight of concrete figures.
3. Density of concrete is taken as:

  • Normal weight (wet) 2400 kg/m3
  • Normal weight (dry) 2350 kg/m3
  • Lightweight (wet) 1900 kg/m3
  • Lightweight (dry) 1800 kg/m3
Section properties (per metre width)
Nominal thickness (mm) Design thickness (mm) Profile weight (kN/m2) Area of steel (mm2/m) Height to neutral axis (mm) Moment of inertia (cm4/m) Ultimate moment capacity (kNm/m)
Sagging Hogging
1.25 1.21 0.17 2118 107.00 968.0 30.80 30.80


Decking material
Corus Galvatite, hot dip zinc coated steel EN 10326-S280GD+Z275. Guaranteed minimum yield stress 350N/mm2. Minimum zinc coating mass 275g/m2 total both sides.

Quick reference tables
The quick reference load/span and fire design tables,in the ComFlor® manual are intended as a guide for initial design, based on the parameters stated below the tables.

Full design can be carried out using the free Comdek software.

Anti-crack mesh
BS 5950: Part 4 currently recommends that anticrack mesh should comprise 0.1% of slab area. The Eurocode 4 recommendation is that anticrack mesh should comprise 0.2% of slab area for unpropped spans and 0.4% of slab area for propped spans. The mesh shown in the quick reference tables complies with EC4 and the design program defaults to these values. Where EC4 mesh rules are used, the mesh may be reduced midspan. The reduced British Standard mesh values may still be used by overriding this default in the design program.

Where forklift truck (or other similar concentrated loading) is expected 0.5% minimum percentage reinforcement should be used over the supports and 2% elsewhere to control cracking. For further information refer to the ComFlor® manual.

Mesh top cover must be a minimum of 15mm, and a maximum of 30mm. Mesh laps are to be 300mm for A142 mesh and 400mm for A193, A252 & A393 mesh.

Technical services
The Technical Department at Corus offers a comprehensive advisory service on design of composite flooring, which is available to all specifiers and users. Should queries arise which are not covered by this literature or by the Comdek software, please contact us.