NOTE This standard governs the materials, fabrication, finishes, fastening, and installation of metal bar grating and hot-rolled floor plate furnished as walking-working surfaces, drainage and trench covers, and access flooring. (1.1)

NOTE The covered products are open-grid bar gratings (carbon steel, stainless steel, aluminum, and fiberglass-reinforced plastic) and solid floor plate (steel checker/diamond plate and aluminum tread plate). Both serve the same architectural role - a slip-resistant, often removable, walking surface - but they are selected and detailed differently, so the requirements below are organized by product family. (1.2)

NOTE Bar grating types covered are welded, pressure-locked, and swaged construction. (1.3)

NOTE Welded grating is the dominant carbon and stainless steel product. Pressure-locked and swaged construction are used primarily for aluminum, where welding distortion and heat-affected-zone loss of temper are undesirable. The grating type, material, and load class are selected together from the manufacturer's load tables; this standard fixes the rules that govern that selection. (1.4)

NOTE This standard does not cover the following related scope items: (1.5)

NOTE The opening-size limit shall be taken from the building code edition adopted by the Authority Having Jurisdiction for the project, because the section numbering of the half-inch sphere rule varies between code editions. (2.3)

NOTE The Contractor shall submit the following action submittals before fabrication: (3.1)

NOTE The Contractor shall submit the following informational submittals: (3.2)

NOTE The Contractor shall submit the following closeout submittals: (3.3)

NOTE Single-sourcing each material type keeps bearing bar height, cross bar pitch, and surface treatment uniform so that adjacent panels sit flush and present a consistent slip-resistant surface. (4.8)

NOTE The grating material shall be selected for the corrosion environment, structural load, and budget of the installation, and the selected material shall be recorded on the drawings or in the datasheet below. (5.1)

NOTE Carbon steel (galvanized) is the default for dry and ordinary exterior service. Stainless steel (Type 304, or Type 316 for chloride or chemical exposure) and aluminum are selected where corrosion resistance, weight, or non-sparking properties govern. FRP is selected for chemically aggressive wet environments such as water and wastewater treatment, where steel and aluminum corrode and weight reduction aids removability. (5.2)

NOTE Aluminum grating and aluminum floor plate shall be isolated from concrete, mortar, and dissimilar metals by an isolating coating, neoprene pad, or non-metallic bearing strip. (5.3)

NOTE Bare aluminum in contact with embedded concrete or carbon steel forms a galvanic cell that corrodes the aluminum at the contact line. Isolation at every bearing and fastener interrupts the cell. (5.4)

NOTE For FRP grating the resin system shall be selected and called out explicitly for the chemical exposure; "fiberglass grating" without a resin designation shall not be accepted. (5.5)

NOTE Isophthalic polyester is the standard corrosion-resistant resin, vinyl ester is selected for strong oxidizers and chlorinated water/wastewater service, and phenolic is selected where a fire-rated surface is required. The resin determines chemical and fire performance, so it is a required selection, not a default. (5.6)

NOTE Grating used on an accessible route or in a means of egress shall have openings that do not permit passage of a 1/2 in. sphere in the direction of travel. (6.1)

NOTE This single rule controls bearing bar spacing more often than load does. ADA Section 302 limits floor and ground surface openings to 1/2 in. maximum in the direction of travel, and the building code applies the same half-inch sphere limit to egress walking surfaces. Standard 1-3/16 in. bearing bar spacing leaves a clear opening that fails this test, so accessible and egress areas require close-mesh grating. (6.2)

NOTE The bearing bar spacing shall be selected from the datasheet below and verified against the governing opening-size rule before fabrication. (6.5)

NOTE Bearing bar depth and thickness shall be selected from the manufacturer's load table for the design span and design load, not chosen by habit. (7.1)

NOTE The bearing bar is the load-carrying member; its depth governs span capacity and its thickness governs robustness in service. For pedestrian and light-industrial platforms, 1 in. and 1-1/4 in. depths cover the large majority of spans, with 3/4 in. reserved for very short spans and 1-1/2 in. and deeper used as spans or loads increase. Thickness is 1/8 in. for standard service and 3/16 in. for heavy or abrasive service. (7.2)

NOTE Cross bars shall be provided at a maximum 4 in. center-to-center spacing for standard W-type grating unless a closer pitch is required by the manufacturer's load table. (7.3)

NOTE Cross bars lock the bearing bars into a panel and distribute concentrated loads between bearing bars. The standard 4 in. pitch is the basis for the published W-type load tables; a closer pitch increases panel weight and is specified only when concentrated-load distribution requires it. (7.4)

NOTE Grating panels shall be designed for the project design live load, and the design live load shall be recorded so the panel span can be verified against the load table. (7.5)

NOTE ASCE 7 establishes minimum live loads: ordinary occupied floor areas are designed for 100 psf, catwalks and light access platforms for a reduced uniform load (commonly 40 to 60 psf), and heavy industrial floors subject to forklift or wheel loads for 250 psf and above per MBG 532. Concentrated-load checks from the load table also apply and frequently govern narrow panels. (7.6)

NOTE Grating deflection under the design uniform load shall not exceed the lesser of L/400 of the span or 1/4 in. (7.7)

NOTE The NAAMM load tables are published on this deflection basis. In architectural settings a stricter comfort limit (often expressed as L/240 perceived bounce) may be specified, but the L/400-or-1/4 in. limit is the structural acceptance criterion for pedestrian grating. (7.8)

NOTE Bearing bar tops shall be serrated for wet, oily, exterior, or otherwise slippery-when-wet walking surfaces. (7.9)

NOTE Smooth bar grating becomes dangerously slick when wet or contaminated and does not satisfy the slip-resistance expectation of OSHA 29 CFR 1910.23 for walking-working surfaces. Serrated bearing bars carry notches in the top edge that bite through surface films. Serration reduces the effective bearing area slightly and adds cost, so smooth grating is retained only for dry interior service. (7.10)

NOTE Cut and exposed bearing bar ends shall be banded with a flat bar of the same material and thickness welded across the cut ends. (7.11)

NOTE Banding closes the open ends of cut bearing bars so they cannot snag, lift, or present a trip edge, and on galvanized grating it eliminates the bare cut faces that otherwise corrode preferentially. Banding is required wherever cut ends are exposed to foot traffic and no toe plate or trim closes them. (7.12)

NOTE Minimum bearing length of grating on its support shall be 1 in. for grating depth up to and including 2-1/4 in., and 2 in. for grating depth of 2-1/2 in. and greater. (7.13)

NOTE Adequate seat length prevents the panel end from rolling off its support under eccentric or impact load. The threshold follows NAAMM MBG 531; deeper, heavier panels carry larger end reactions and need the longer seat. (7.14)

NOTE Solid floor plate shall be furnished only where a continuous, non-draining walking surface is required; open grating shall be used where drainage, ventilation, or light passage is required. (8.1)

NOTE Floor plate and grating are frequently shown interchangeably as generic "platform" on layout drawings, which is a common coordination error. Floor plate sheds liquids and blocks light and airflow; grating drains and ventilates. Confirm the functional intent before selecting between them. (8.2)

NOTE Steel floor plate shall conform to ASTM A786, with raised pattern (diamond/4-way, 2-way, or raised bar) as scheduled. (8.3)

NOTE ASTM A786 governs the pattern dimensions, mechanical properties, and permissible thickness variation of hot-rolled floor plate. The diamond (4-way) pattern is the default for general walking surfaces; 2-way and raised-bar patterns are selected for directional traction. (8.4)

NOTE Floor plate in wet or washdown areas shall be furnished with an applied anti-slip grit surface or abrasive nosing strips at the leading edges. (8.7)

NOTE The raised diamond pattern improves traction but does not make floor plate slip-resistant when wet; the smooth field between ribs remains slick. An applied grit coating or abrasive nosing at step and ramp edges provides the wet slip resistance the pattern alone cannot. (8.8)

NOTE Carbon steel grating and floor plate shall be hot-dip galvanized after fabrication in accordance with ASTM A123, Grade 65 minimum (2.0 oz/ft² average coating weight). (9.1)

NOTE Galvanizing after fabrication coats the cut ends, welds, and banding that would otherwise be the first points of corrosion. It is the dominant finish for exterior and exposed industrial grating. Grade 65 sets the minimum average coating weight for the fabricated assembly. (9.2)

NOTE Hollow or closed sections within fabricated panels to be galvanized shall be provided with vent and drain holes coordinated with the galvanizer before fabrication. (9.4)

NOTE Sealed cavities trap moisture or cleaning solution that flashes to steam in the molten zinc bath, which can warp the panel or cause a violent ejection of metal. Vent and drain holes let the cavity fill and drain safely. (9.5)

NOTE Field-damaged galvanized coatings shall be repaired in accordance with ASTM A780. (9.6)

NOTE Cutting, welding, and handling inevitably break the shop coating; A780 zinc-rich or sprayed-zinc repair restores the cut-edge and weld protection that field exposure would otherwise attack. (9.7)

NOTE Stainless steel and FRP grating shall be furnished in their natural finish and shall not be coated unless an architectural finish is scheduled. (9.8)

NOTE Stainless and FRP are corrosion-resistant in their as-supplied state; a coating adds cost and a maintenance liability without improving durability. Anodizing or paint on aluminum, and any architectural finish on stainless, are specified only when the appearance is scheduled. (9.9)

NOTE Grating panels shall be anchored to their supports by saddle clips, welds, or bolted connections as required by the removability and uplift conditions of the installation. (10.1)

NOTE Saddle clips are the standard fastening and allow panels to be lifted for access. Welding is used where panels are permanent and uplift or vibration is a concern. Bolted connections are used where a removable but positively secured connection is required. (10.2)

NOTE Panels over equipment, valves, or services that require maintenance access shall be removable and shall be fastened with saddle clips or bolts, not welded. (10.3)

NOTE Welding a panel shut over equipment that must later be reached generates a field change order to cut it out. Removable fastening is a coordination requirement, not merely a convenience, wherever access below the grating is foreseeable. (10.4)

NOTE Grating panel size shall be limited so that any panel intended for manual handling does not exceed 50 lb; heavier panels shall be split into multiple sections or detailed for mechanical lifting. (10.6)

NOTE A panel designed only for its full structural capacity often exceeds a safe two-person manual lift, which produces field RFIs to split it. Setting a handling weight limit up front, or calling out mechanical lifting, avoids that rework and keeps maintenance access practical. (10.7)

NOTE Where grating abuts an open-sided platform edge, a toe board (kick plate) of the height required by the governing building code shall be provided; the code minimum is 3-1/2 in. (11.1)

NOTE The toe board prevents tools and debris from being kicked off the platform edge onto workers below and closes the gap between the walking surface and the guardrail. The 3-1/2 in. minimum is the common code value; confirm against the adopted code edition. The toe board and guardrail assembly itself is furnished under Metal Stairs And Railings, but the grating edge must be detailed to receive it. (11.2)

NOTE Bearing bar depth shall be held uniform across adjoining panels within a continuous walking area so that adjacent panel surfaces are flush. (11.3)

NOTE Mixing bearing bar depths across a continuous floor produces a step-up at the joint between panels, which is a trip hazard. Where different depths are unavoidable (different spans), the supports shall be set at different elevations so the walking surfaces remain flush. (11.4)

NOTE Support framing for grating panels shall be coordinated with the grating load table so that the support spacing does not exceed the allowable span of the selected bearing bar. (12.2)

NOTE Support framing is frequently laid out independently of the grating it carries, which can leave a panel spanning farther than its load table allows. (12.3)

NOTE Aluminum and stainless panels shall not be cut, drilled, or ground with tools or abrasives previously used on carbon steel. (12.9)

NOTE Embedded carbon steel particles rust on a stainless or aluminum surface and create a corrosion site that looks like a defect in the base metal. Dedicated, non-contaminated tooling preserves the corrosion resistance the material was selected for. (12.10)

NOTE Panels shall be stored off the ground on dunnage, sloped to drain, and protected from standing water and mud. (13.2)

NOTE Galvanized and FRP panels stacked flat in standing water develop wet-storage staining (white rust on zinc) and trapped grit; sloped, dunnaged storage keeps the surfaces drained and clean until installation. (13.3)

NOTE The Contractor shall warrant grating and floor plate materials and installation against defects in material and workmanship for a period of not less than one year from Substantial Completion. (14.1)

NOTE The one-year correction period is the project-standard floor for fabricated metal work. Coating systems may carry a longer manufacturer warranty where scheduled. (14.2)

NOTE The Contractor shall furnish spare saddle clips and fasteners equal to 5 percent of the installed quantity, and not fewer than one box of each clip type used. (15.1)

NOTE Removable grating loses clips during maintenance access; a small clip stock lets the owner re-secure lifted panels without a procurement cycle. Spare full panels are furnished only where called out for high-traffic or impact-prone areas. (15.2)