Moulded Grating VS Pultruded Grating: Which One is Better?

To understand the differences between moulded and pultruded grating, it is important to know exactly what Glass Reinforced Plastic (GRP) is. GRP is an alternative to traditional industrial materials, such as steel, concrete, and wood. It is made by combining resin with fibreglass. Resin formulations, resin proportions, and manufacturing techniques allow this product to be used as gratings, handrails, ladders, platforms, and custom engineered solutions. Often people ask, “What is the difference between moulded and pultruded grating?” Fibergrate wants to help people make the right decision when it comes to choosing the right material for their next project. Some people might simply say: “Moulded grating is a panel that has a square or rectangular top mesh whereas pultruded grating is composed by a series of parallel bars.” Is it really this simple? Please allow us to explain.

Differences Between Moulded and Pultruded Grating

#1: Surface

Surface is a big differentiator. Moulded grating and pultruded grating are available in a variety of surfaces to best fit the requirements of an application and create a safe environment. Available surface options include:

• Meniscus Top: The concave surface of meniscus top grating provides superior slip resistant footing in most environments including wet or oily conditions. Meniscus top is not suitable for barefoot traffic.
• Integrally Applied Grit Top: This optional grit top grating has a quartz grit which is integrally applied, cured and sealed onto the surface providing excellent slip resistant footing.
• Aluminium Oxide Grit: This surface is highly durable and provides secure footing for maximum safety.
• Smooth: This grating surface has been sanded down to create a surface with a smooth finish.
• Aqua Grit: This surface offers optimum comfort and safety for people walking with bare feet. 

Moulded Grating - Moulded grating offers more surface options than pultruded grating. Surface options for moulded grating are meniscus top, integrally applied grit top, aluminium oxide grit, smooth surface, and aqua grit. The top of this grating can be square or rectangular mesh.

Pultruded Grating - Pultruded grating offers three types of surfaces: integrally applied grit top, aluminium oxide grit, and aqua grit. You will be able to distinguish this grating because its top is composed by a series of parallel bars that have been assembled, not molded.

#2: Manufacturing

Moulded Grating – Moulded grating was invented by William C. Coonrod in 1966 in Dallas, Texas. With that panel, Coonrod started Fibergrate. The fabrication process consists of applying interlaced layers of liquid resin and long continuous fibreglass strands inside an open mould (the combination consists of more resin than fibreglass) until the desired thickness of the grating is achieved. Once this happens, the panel is left to cure. The interwoven square mesh construction will give the product bi-directional strength meaning the panel will be able to carry the same load no matter which direction the load on top of the grating moves.

Pultruded grating - Pultruded grating consists of more glass than resin. This type of grating is created by a series of parallel load bars that are kept parallel by a series of cross rods. These bars are fabricated by pulling fibreglass roving through a pultrusion machine. Then, the fibreglass receives a resin bath, and it is wrapped with a surface veil made out of fibreglass strands. These veils reinforce the bars. Once the bars are ready, they are assembled and turned into pultruded grating. Pultruded grating has unidirectional strength which makes it the ideal choice for applications with high load demands or long spans. 

#3: Resins

Moulded Grating - Moulded grating offers a wide variety of resins to help you cover different needs. Fibergrate's moulded grating resin systems include: 

• Vi-Corr^®: This is a superior vinyl ester resin that offers an incredible corrosion resistance in highly acidic environments. Available colours are orange or dark grey.
• FGI-AM^®: This is a food-grade isophthalic polyester resin system that offers antimicrobial properties to inhibit the growth of bacteria on the surface. Available colours are light grey or green.
• Corvex^®: This is a isophthalic polyester resin system is ideal for highly corrosive environments such as industrial, chemical processing, and water/wastewater applications. Available colours are yellow, dark grey, or dark green.
• XFR: XFR stands for eXtra Fire Retardant. This is a vinyl ester resin, and it is recommended for applications where the fire potential is high. Flame Spread is ASTM E84 rating of 100 or less, a level exceeded by no other resin system. Available in dark grey.
• ELS: ELS stands for Extremely Low Smoke. This resin is an acrylic-modified polyester system ideal for tunnel, offshore, mass transit, and other confined space applications. ELS exhibits low ignitability, low smoke generation, and extremely low smoke toxicity. Flame Spread is ASTM E84: flame spread index of 25 or less, with a smoke developed index of 100 or less and Fuel Contribution of 0. Available in a dark grey.
• Super Vi-Corr^®: This is a family of resin systems that consists of more than 30 custom formulae engineered to provide control solutions in application that are too severe for conventional GRP and other building materials. Each Super Vi-Corr resin was engineered for the best possible performance in specific chemical and/or elevated temperature environments. These systems exist for aggressive chemical service in reagents like solvents, acidic oxidizers, chlorine dioxide, sodium hypochlorite, and liquid desiccants. Certain formulas are also suited for elevated temperature applications up to 400° F. Gratings made with Super Vi-Corr resin are typically used for packing hold-downs and support in environmental and process scrubber applications. They are available in natural - tan to beige colours. The flame spread is non fire retardant, unless specified.

Pultruded Grating - Pultruded grating on the other hand offers three resin systems:

• ISOFR: This is an isophthalic polyester resin formulation ideal for applications where there is a moderate exposure to corrosive elements. This resin has a low flame spread rating of 25 or less.
• VEFR: This is an vinyl ester resin system with a flame spread of 25 or less for dependable resistance to both acidic and alkaline environments.
• Phenolic: This is a Coast Guard approved flame-resistant phenolic resin. If unpainted, it can have an extremely low flame spread of 10 and a smoke index of 400. If it is painted or has a UV coating, it can have flame spread of 15 and a smoke index of 450. This resin is designed primarily for the offshore industry (Coast Guard approved for Level 2 & 3 performance criteria - Approval Number: 164.040/2/2; DNV GL Type Approval No. TAF000003C; ABS Product Type Approval Level 2 & 3 Certificate No. 01-HS34733-X).

Which grating is stronger?

Both moulded and pultruded grating have grating configurations that are strong enough to carry vehicular loads while still being less than one-half the weight of steel grating. Moulded grating has a higher resin concentration making the panels more flexible and impact resistant than pultruded grating. Glass reinforcement provides structural strength to both gratings. Pultruded grating has a higher fibreglass concentration making it the stronger grating. It is important to note that moulded grating is a better solution for shorter span applications and pultruded grating is a better solution for longer span applications.

Fibergrate has two grating options with a high load capacity that will help you decide which grating is better for your next project.

High Load Moulded Grating: Moulded High Load Capacity (HLC) grating is engineered and manufactured to carry forklift loads that traditional moulded GRP grating is unable to support. HLC moulded grating is available in Fibergrate’s Vi-Corr, Corvex, and FGI-AM resin systems with either a smooth top or an aluminium oxide grit top surface. High load moulded grating is optimal for trench covers and ramps, in storage and loading areas, or in other areas that necessitate a product that can withstand vehicular turning traffic. HLC grating is offered in 1-1/2” and 2” depths in a 6’ x 4’ panel size.

High Load Pultruded Grating: High Load Capacity (HI) pultruded grating has been engineered to carry the forklift and tractor trailer loads that traditional pultruded GRP grating products are unable to support. If your application involves turning traffic on the grating, please look into HLC Moulded Grating. HI is available in 1”, 1-1/2", 2", 2-1/2", and 3" depths and 37%, 47%, and 58% open surface area.

Which grating is better for me?

Now that we have explained how to differentiate moulded and pultruded grating based on their appearance, the fabrication process, resin systems, and surface options, we hope this helps you identify the type of grating you need for your next project. Please keep in mind that both moulded and pultruded grating share amazing benefits, and depending on the application, one may be more favorable then the other. Remember, we have a sales manager in your area ready to assist you in every step of the buying process.