Checkered floor plate

What it is

Checkered floor plate (also called chequer plate, tread plate or diamond plate) is hot-rolled steel plate with a raised pattern on the top surface. Unlike bar grating it gives a solid floor, so it is used where liquids, small parts, sparks or light must not pass through: platforms over electrical equipment, covers over pits and trenches, vehicle ramps, machine bases, step plates, and kick plates at the edge of platforms.

Floor plate is heavier than grating for the same span and needs stiffeners on larger panels, but it can be combined with grating in the same platform – for example solid plate under a valve station and grating elsewhere.

Types and options

Material is specified by region: ASTM A786 rolled floor plate (with A36 or a similar mechanical grade) in the US, AS/NZS 3678 floorplate in Australia and New Zealand, and EN 10025-2 steel such as S235 or S275 with a chequer pattern to DIN 59220 in Europe.

Design and compliance

A floor plate panel is designed as a plate spanning one or two ways between supports. The governing check is usually deflection under the specified floor load or a concentrated load, rather than strength; stiffeners are added where the plate would otherwise become too thick. Floor loads come from ASCE 7 in the US (for example 125 psf light manufacturing, 250 psf heavy manufacturing), AS/NZS 1170.1 in Australia and EN 1991-1-1 in Europe; the deflection limit is set by the designer.

• Floor plate is slippery when oily or wet. Where slip resistance is critical, consider serrated grating, an abrasive coating, or classifying the surface to AS 4586.
• Plates must be drained or laid to a fall outdoors; ponding water shortens coating life.
• Where plate forms part of a platform, guardrails, toe plates and access widths follow the platform rules (OSHA 1910 Subpart D, AS 1657, EN ISO 14122-2).
• For trafficked covers the plate and frame must meet the load class of AASHTO, AS 3996 or EN 124 – see heavy-duty grating.

Fabrication and finishing at World Steel

Plates are CNC-cut to the layout, drilled or countersunk for fixings, and stiffeners are welded underneath with intermittent or continuous welds as detailed. Continuous sealing welds are preferred where panels will be galvanized, to avoid trapped pickling acid between stiffener and plate; vent and drain holes are added to hollow details. Welding follows AWS D1.1, AS/NZS 1554.1 or EN ISO 3834-2 procedures.

Large flat plates can distort in the galvanizing bath; panel size, thickness and stiffener layout are reviewed before galvanizing, and a painted finish may be proposed for thin, large panels. Painting follows blast cleaning and painting procedures to SSPC-SP 6/SP 10, AS/NZS 2312.1 or EN ISO 12944.

Installation and specifying

Panels are shipped flat on timber bearers, marked to the layout. Check support levels before laying, fix with all specified bolts or clips, and repair any galvanizing damaged by site welding with zinc-rich paint. To quote, World Steel needs the layout, design load, plate thickness or deflection limit, pattern, finish and fixing type – or the full platform model so the plate can be detailed with the supporting steel.