Pultruded vs Molded FRP Grating: How to Choose

Choose molded for impact resistance, bi-directional strength and economical short spans; choose pultruded for long spans, heavy loads and high stiffness. The two processes are not interchangeable — they put the glass in different directions at different fractions — and most mixed-use projects correctly use both, each where it is best. This article sets the selection rule out in numbers.

1. The Manufacturing Difference

Molded grating is compression-formed from chopped-strand mat and woven roving with a rich resin matrix; the glass is laid up in both panel directions. Pultruded grating is pulled as continuous rovings through a heated die to form bearing bars (I/T profiles) assembled with tie-bars; the glass is aligned almost entirely along the bar length. That single difference explains every performance number below.

2. Side-by-Side (typical / indicative)

3. Span and Load — Where Each Wins

Because pultruded bearing bars are packed with aligned glass at ~70% content, they are roughly twice as stiff per kilogram as molded sections. That converts directly into span: molded panels are efficient out to about 1.2–1.5 m, while deeper pultruded sections reach 1.8–3 m before an intermediate support becomes cheaper than a deeper bar. Beyond ~3 m, introduce an FRP or steel sub-frame rather than over-sizing the grating.

4. Impact and Direction

Molded's bi-directional mat-and-woven layup gives it genuine toughness: a dropped tool or cart deflects and absorbs, rather than snapping a single aligned bar. Pultruded bars are strong but directional — lay them with bearing bars across the short span; laid parallel, the panel carries load through weak tie-bars and is the single most common field error. Molded gratings have no orientation sensitivity.

5. Cost and Resin Options

For short spans and moderate pedestrian loads, molded is the more economical panel per m² and tolerates abuse. For long spans or heavy industrial loads, pultruded's stiffness means a lighter, fewer-supports panel that is cost-effective overall. Both are available across the resin range — isophthalic (ZeAll ISO), vinyl ester (ZeAll VE), novolac VE, fire-retardant (ZeAll FR) and food/potable grades — so resin selection is independent of the molded-vs-pultruded choice.

6. Decision Summary

• Choose molded when: span ≤ ~1.5 m; impact / dropped-tool exposure; wet process or chemical areas; orientation flexibility is valued; open area / mesh options matter.
• Choose pultruded when: span ~1.8–3 m; heavy or mezzanine loads; deflection must be tightly controlled; minimum weight and fewest supports are wanted.
• Use both: molded in the process/impact areas, pultruded on the main long-span walkway — the common, cost-optimized plant solution.

7. Open Area, Cutting and Fixing

The two processes offer different design freedoms. Molded grating gives a choice of mesh openings — fine Mini-Mesh for wearing heels and small parts, standard 38×38 mm for drainage and light footfall, rectangular mesh for maximum open area — and, because strength is bi-directional, holes for pipes and equipment can be cut in the panel without immediate reinforcement (up to about one-third of the panel width). Pultruded grating has a fixed tie-bar spacing and is drilled rather than cut arbitrarily; openings generally need a pultruded edge frame. Molded edges also band easily where personnel pass through, while pultruded bar ends are usually capped or banded to protect the aligned glass.

8. Cost in Context

Per square metre, molded is usually the cheaper panel for short spans, and pultruded becomes the better value only when its longer span removes a row of support beams. The cheapest installed solution is rarely one product throughout: molded in the impact-prone process bays and around equipment, pultruded on the main access walkway and over long pipe racks. Over-specifying pultruded for a 1 m walkway pays twice — heavier panel and unnecessary stiffness; under-specifying molded for a 2.5 m span buys a deflection problem and a retrofit. Send both spans and loads; the optimum mix is the engineer's answer, not a product default.

Send your span, load, deflection criterion and environment; ZeAllgrate manufactures both families and will recommend on your application rather than our inventory, with certified load/span tables for each.