Molded vs Pultruded Fiberglass Grating

The difference is how each is made. Molded grating is cast as a one-piece panel in a mold, so it has bars and strength in both directions. Pultruded grating is assembled from pultruded bearing bars joined by cross rods, commonly 6" (152 mm) on center, so its strength runs mainly along the bars.

That makes molded grating resin-rich, typically about 30–35% glass by weight, and pultruded grating glass-rich, typically about 65–70%. US makers market pultruded grating as about twice as stiff as molded, which is why it spans farther between supports. Strongrate makes both types in Nantong, China; its catalog gives 30–35% glass for its molded grating and 60–65% for pultruded, and its DNV certificate lists four molded and two pultruded models.

US makers market pultruded grating as about twice as stiff as molded, which is why it is chosen for longer spans; treat that as a marketing comparison and check real tables. Do not compare makers’ tables at face value: published safe loads rest on safety factors from 2:1 to 5:1 on ultimate capacity. Compare deflection at your span and design load, using tables tested to the ANSI/ACMA FGMC grating manual.

Common walkway deflection limits are 3/8" (9.5 mm) or L/120 for comfort and 1/4" (6.4 mm) where a firmer feel is wanted.

Strongrate’s 2023 catalog prints deflection tables for its molded meshes by depth and for its pultruded types under uniform and line loads (molded also under point loads), static at ambient temperature, and says to halve the loads for impact or dynamic conditions. The tables are on fiberglass grating load tables; confirm values in your quote and submittal drawings before design use.

At 1-1/2" (38 mm) and 2" (51 mm) depths, published pultruded weights are lower than molded weights; at 1" (25 mm) they are about the same. In Strongrate’s catalog, its 60%-open I-bar and 50%-open T-bar types weigh less than its square-mesh molded grating at all three depths. Mesh and open area change weight too, so use the figure for the exact product.

Standard molded grating is about 70% open in 1-1/2" square mesh, against about 40% or 60% for pultruded I-bar and 33% or 50% for T-bar. For an accessible route, ADA 302.3 bars openings that pass a 1/2" (13 mm) sphere; mini-mesh molded grating sold for ADA use, with a 3/4" (19 mm) top mesh over a 1-1/2" (38 mm) base, is typically about 44% open.

On an accessible route, elongated openings, such as the slots between pultruded bars, must run with the long dimension perpendicular to the dominant direction of travel. Strongrate’s catalog lists its square-mesh molded grating at 52–84% open, its mini meshes at 30–60%, and its pultruded types at 40–83% (I-bar) and 12–50% (T-bar); check the measured clear opening before any accessible-route use. See mini mesh ADA grating.

Chemical resistance depends on the resin system. US grating resins include isophthalic polyester for general industrial use, vinyl ester for harsher chemical service, food-grade isophthalic and phenolic for marine and offshore work. Molded grating is a common choice for chemical plants, and on pultruded grating drilling can compromise the corrosion barrier, so seal every hole.

Strongrate’s catalog lists fire-retardant vinyl ester and isophthalic polyester (including a food-grade isophthalic) for both molded and pultruded grating, and orthophthalic polyester for molded only; its six DNV-listed models use vinyl ester, isophthalic and orthophthalic. The catalog’s chemical-resistance chart rates each resin by chemical; it is on fiberglass grating specifications. Send your chemicals, concentrations and temperatures with your quote request.

Usually, up front. A US distributor notes that pultruded grating usually costs more upfront, and FRP price guides (2025 or undated, read Oct 15, 2026) put molded grating at about $12–$18 per sq ft against $20–$28 for pultruded. It is not a rule: one US maker has priced its stocked pultruded grating at parity with equivalent molded grating since 2017.

Use the table as a first pass, then confirm with load tables at your span. Two cases need care with Strongrate grating: vehicle traffic, where only its HI high-load pultruded types have catalog spans under wheel loads, subject to your engineer’s review; and federally funded projects under Build America, Buy America, which China-made grating does not qualify for.

Six Strongrate models have documented data today, all from DNV Type Approval TAF0000191 Rev. 1: four molded and two pultruded. Their ASTM E84-19a flame spread indexes run from 5 to 20, all at or below 25. The approval is a fire-technical evaluation only; it does not cover load capacity.