Fiberglass Grating

Fiberglass Grating is ideal when you require a product that is highly resistant to corrosive environments, fire retardant, non-conductive, light weight, low maintenance or architecturally attractive. Common uses for fiberglass grating include:

  • Drain covers
  • Trench covers
  • Covered gratings
  • Platforms
  • Stair treads

Fiberglass Grating Products:

Fiberglass Overview

The two primary manufacturing processes used to produce Marco FRP Grating products are Pultrusion and Open Molding. Both processes produce high quality, uniform construction.

High quality, well designed, pultruded grating, which resembles metal bar grating, is stronger, lighter, equally corrosion resistant, and in most cases, is less expensive than molded grating. Additionally, pultruded grating comes in larger panels and can be built to custom panel sizes. In most applications, pultruded fiberglass grating will represent the best product and the lowest price.

Molded fiberglass grating has equal strength in both directions and is made with square or rectangular grid patterns. Since it was developed much earlier than pultruded grating, it is widely used and performs well in many applications.

Download entire Molded and Pultruded Fiberglass Grating Catalog in PDF format

Comparison of Molded and Pultruded Grating:

Molded Grating Pultruded Grating
Imagine a giant 4 ft x 12 ft waffle iron (mold). Liquid resin and continuous fiberglass roving are systematically laid in the mold, layer after layer manually, to produce the desired thickness and panel dimensions. The finished molds are set aside for a predetermined time to allow the panel to cure. The panel is then ejected from the mold. The molds are cleaned and prepared for the process to begin again.

The one piece interwoven square mesh construction of molded grating produces two primary benefits: maximum corrosion resistance and high strength.

Because the grating is "cast" in one piece, there is no mechanical joint between bearing bars, unlike the pultruded grating where the glued joints can give way in heavy continuous traffic or after prolonged service.

The high percentage of resin (65%) in molded grating offers superior corrosion resistance. The molded grating with a square mesh pattern offers increased load capacity and panel utilization due to this bi-directional trait.

Cutting access holes in the molded grating does not weaken the panel and does not require additional or costly supports (unlike pultruded grating that must be re-supported and edge-banded).
The pultruded grating product is a mostly mechanized process. Fiberglass of different shapes such as: strand, mat and veil are pulled through a liquid resin bath and a heated die where the bar is shaped and the resin is cured. These pultruded bars can be cut into 12 ft, 15 ft or 20 ft lengths. The bars are then taken to a workstation and drilled (6" or 12" on center) on the sides to accept the crossbars. The drilled bars are spaced proportionally for the width of the panel; 3 ft, 4 ft or 5 ft. The final step is to seal the entire cross bars and holes with corrosion resistant epoxy resin.

The pultruded grating provides increased load capacity with moderate levels of corrosion resistance. The components (bearing bars and cross bars) are pulled by machine to have a higher glass content. Its superior load capacity to molded grating is a result of the higher glass to resin ratio (65% glass to 35% resin). However, the lower resin content reduces the corrosion resistance as compared to the molded grating.

The pultrusion process is automated and produces a consistent, high quality finished product.

Assembled from bars, the pultruded grating can offer a wide variety of panel sizes and substantially reduce "scrap loss" not always possible from molded grating panels.
Open Molded Grating
  • Isophthalic- Your choice against acids and other chemicals commonly found in most industrial and chemical processing applications. Flame spread rating is Class I, 25 or less when tested in accordance with ASTM E84. Isophthalic Base
  • Vinyl Ester- The strongest resin system available to protect against caustics and acids found in the toughest environments. Flame spread rating is Class I, 25 or less when tested in accordance with ASTM E84. Vinyl Ester Base
  • Food Grade-A resin designed for USDA food processing applications. Flame spread rating is ClassII, 75 or less when tested in accordance with ASTM E84. Isophthalic Base
  • Extra Fire Retardant- Used when the lowest flame spread rating is required. Flame spread rating is Class I, 10 or less when tested in accordance with ASTM E84. Isophthalic Base
  Pultruded Grating
  • Isophthalic- Good corrosion resistance in moderately corrosive industrial areas. Flame spread rating is Class I, 25 or less when tested in accordance with ASTM E84. Isophthalic Base
  • Vinyl Ester- Highly resistant to both acidic and alkaline environments. Flame spread rating is Class I, 25 or less when tested in accordance with ASTM E84. Vinyl Ester Base
  • Food Grade-USDA approved resin for food processing applications
  • Phenolic- Good corrosion resistance and excellent fire and smoke resistant. ASTM E84 Class I, flame spread rating of 15 or less and smoke developed of 50 or less.

Ordering Information

Please review the following Ordering Information:


  1. Application or use of product
  2. Physical requirements
    a. exposure to chemicals and/or extreme temperatures
    View Resistance Guide
    (Adobe Acrobat Reader Required Download free reader)
    b. fire retardant rating
    c. loading requirements, span and support systems

Please Specify:

  1. Type:
    a. Molded - rectangular or square
    pattern and mesh size
    b. Pultruded - I-Bar or T-Bar
  2. Resin & Color:
    minimums may apply--please inquire
  3. Quantity:
    number of panels, areas or
    treads--full size or cut pieces required.
  4. Height:
    a. Molded --panel height
    b. Pultruded--bar height
  5. Width:
    width of panel, plank or pieces.
  6. Length:
    length of panel, plank or pieces
  7. Surface:
    plain or with grit
  8. For Pultruded I-Bar or T-Bar planks:
    indicate spacing between bearing bar centers
    and cross bar centers. Also indicate span of
    bearing bars shown in diagrams)
    For Molded/rectangular panels: indicate span shown in diagram
  9. Special Fabrication:
    cut-outs, etc.
  10. Fasteners:
    type, size, hardware

M Clips
M Clips
C Clips
C Clips
L Clips
L Clips
Pawl Clips
Pawl Clips
G Clips ( Part A & B )
G Clips ( Part A & B )
CSSM Clips ( Part A & B )
CSSM Clips ( Part A & B )
J Clips
J Clips
T Clips
T Clips
>W Clips
W Clips

Specs & Info

For more in-depth information specific to our Fiberglass products, download the PDFs below:

Contact one of our sales representatives today
to inquire about a quote from Marco Specialty Steel, Inc.

Request a Quote

Have a Question?

* denotes required fields.


Scroll To Top