Fiberglass Grating Buying Guide

Fiberglass grating buying guide: pin down the construction type (molded or pultruded), resin system, panel size and depth, bearing bar spacing, load and deflection limits, surface finish, and the environment it will live in. Get those eight items on one page and any competent manufacturer can size the grating, quote it accurately, and flag failure modes you haven’t thought of. Here is how to spec each one.

Step 1: Molded or Pultruded?

This is the first fork in the road, and it decides almost everything downstream.

Molded grating is cast in a one-piece square or rectangular mesh. Loads spread in both directions, so it tolerates cutouts, pipe penetrations, and irregular support layouts without losing much strength. The high resin content also gives it excellent corrosion resistance, which is why it dominates chemical plants and plating lines.

Pultruded grating is built from load-bearing bars that are pulled through a die and then locked together with cross rods. The glass runs in one direction, so strength runs in one direction — but in that direction it carries far more load over longer spans. It also sits better in wide walkways, docks, and anywhere you want a structural, beam-like load path.

Rule of thumb: if the drawing is full of cutouts, go molded. If the drawing is full of long straight spans, go pultruded.

Step 2: Pick the Resin System

The glass provides the strength; the resin decides how long the grating survives your environment. Three families cover most projects:

• Polyester (ortho or isophthalic) — the default for general industrial service, moderate corrosion, and outdoor exposure. Standard fire-retardant polyester systems commonly achieve Class 1 flame spread under ASTM E84.
• Vinyl ester — the upgrade for aggressive chemistry: acids, alkalies, caustics, bleach, pickling areas, and severe marine service. It costs more, and in genuinely corrosive environments it is almost always worth it.
• Fire-retardant formulations — specify explicitly when the project has a flame-spread requirement or sits under a building code. Don’t assume a standard resin meets it.

If you’re not sure which resin you need, send the supplier the chemical list and concentration, not a guess. “Mild chemicals” means nothing; “10% sulfuric acid splash zone at ambient temperature” gets you the right panel.

Step 3: Size, Spacing, Load, and Deflection

This is where quotes go wrong. Vague answers here mean the supplier either over-builds (you overpay) or under-builds (the panel deflects like a trampoline). Spec these five items:

1. Panel size and depth. State width and length — common stock widths are 3, 4, and 5 ft, with lengths of 8, 10, 12, and 20 ft — plus grating depth. Depth drives stiffness: moving from 1 in to 1.5 in molded grating roughly doubles load capacity at the same span.
2. Bearing bar spacing. For molded grating, give the mesh pattern or cross-rod spacing, such as 6, 8, or 12 in on center. For pultruded grating, give the bar spacing and whether you need an open or closed top.
3. Load rating. Provide the design uniform load (psf) and any concentrated point load (a pallet jack wheel, a forklift axle), plus the clear span between supports. The span matters as much as the load — capacity falls off fast as span grows.
4. Deflection limit. State what movement is acceptable. Common practice is around L/100 for molded and L/180 for pultruded grating, and many engineers add a 1/4-in absolute limit so walkways feel solid underfoot. A grating can be structurally safe and still feel alarming to walk on.
5. Surface. Concave (meniscus) is standard and self-draining. Grit tops are the choice for oil, ice, or steep slopes. Covered or solid-top panels exist where debris falling through is a problem.

Step 4: Match It to the Environment

Cross-check the application before you finalize the spec:

• Walkway / platform: molded or pultruded, decided by span and traffic; add grit if the surface gets wet or oily
• Chemical area: vinyl ester or another chemical-resistant resin, with the actual chemical list sent to the supplier
• Marine / wet / corrosive: vinyl ester, UV-stabilized, grit surface
• Fire-sensitive area: fire-retardant resin, typically specified to Class 1 (ASTM E84) flame spread
• Food and washdown: resin and surface that tolerate repeated hot-water and sanitizer exposure — confirm this explicitly, it’s a different duty than splash corrosion

Buying Checklist: What to Send the Supplier

A complete inquiry gets a firm quote in one round instead of four. Include:

• Construction type: molded or pultruded (or “open to recommendation” with your span and loads)
• Resin system, and the actual chemicals / environment if you’re unsure
• Panel dimensions and depth, plus total area and how many panels
• Bearing bar spacing or mesh pattern
• Uniform load, point loads, clear span, and support layout
• Deflection limit
• Surface: concave, grit, or covered
• Fire-rating requirement, if any
• Cutting, banding, and edge treatment needed
• Fastener / clip requirements (M-clips, J-clips, hold-downs)

Sample Purchase Specification

FRP grating, [molded / pultruded], [resin], [fire-retardant yes/no],
[panel size], [depth], [bearing bar spacing],
designed for [uniform load], [point load], [span],
with max deflection of [limit],
surface [concave / grit / covered],
for [walkway / platform / chemical / marine] service.

See our pultruded FRP grating for standard constructions, or our pultruded FRP profiles if your project also needs structural shapes from the same supplier.

Common Buying Mistakes

Three errors account for most grating problems in the field. First, specifying by depth alone — two 1.5 in panels with different bar spacing and glass content are not the same product. Second, ignoring deflection feel: a panel that passes the safety calc at L/60 will still bounce underfoot and earn complaints. Third, leaving resin selection to the supplier without telling them the chemistry. The cheapest panel that fails in three years is the most expensive one you’ll ever buy.

FAQ

Molded or pultruded FRP grating — which should I choose?

Choose molded when you need two-way strength, frequent cutouts, or maximum corrosion resistance. Choose pultruded when you need to carry higher loads over longer spans in one direction. When in doubt, send the span and load to the supplier and let the calculation decide.

What resin is best for FRP grating?

Polyester covers general industrial and outdoor service. Vinyl ester is the pick for acids, caustics, bleach, and marine exposure. Where flame spread is regulated, specify a fire-retardant system — typically Class 1 under ASTM E84.

What deflection limit should I use for FRP grating?

Common practice is about L/100 for molded and L/180 for pultruded grating, often with a 1/4-in cap so walkways feel firm. State your allowable deflection when ordering; don’t leave it as an assumption.

What loads do I need to specify for FRP grating?

Give the uniform load, any concentrated point loads (wheels, equipment feet), and the clear span between supports. With those three numbers the supplier can confirm panel depth and bar spacing.

Can FRP grating be fire rated?

Yes. Fire-retardant resin systems, including Class 1 (ASTM E84) polyester and vinyl ester options, are widely available. Specify the rating your code requires rather than asking for “fire resistant.”

Specifying FRP grating for a project? IncomePultrusion is a factory-direct FRP pultrusion manufacturer in Nanjing — send us your span, loads, environment, and finish, and we’ll size molded or pultruded grating to match, including custom panels and OEM work. Contact us for a quote.