FRP Grating Types: How to Classify Them

FRP grating types are classified in more than one way. Molded and pultruded describe the construction method; open-grid and covered or solid-top describe the top configuration; opening terms describe the mesh; and smooth, concave, or gritted describe the walking surface. These labels are not interchangeable, so a complete requirement may need one term from each category.

We offer molded and pultruded fiberglass grating. Classification labels identify one aspect of the panel; dimensions, load capacity, span, material system, tested performance, and availability come from product-specific documentation.

The Four Classification Dimensions

The word type can refer to construction, top configuration, opening pattern, or surface. Separating these dimensions prevents a surface term from being mistaken for a structural product type.

Classification dimension	Examples	What the label tells you	What still needs verification
Construction	Molded; pultruded	How the grid or its load-bearing components are formed	Panel geometry, bearing direction, support conditions, load/span data, and product documentation
Top configuration	Open-grid; covered; solid-top	Whether the top has open passages or a more continuous surface	Cross-section, how the top is formed or attached, drainage needs, support details, and available combinations
Opening pattern	Open mesh; narrower opening; supplier-specific mesh names	The general form of the openings	Actual opening dimensions, open area, object-passage requirement, and product-specific terminology
Surface	Smooth; concave; gritted	The finish at the top of the panel	Surface construction, applicable test method, operating conditions, wear, and cleaning requirements

A phrase such as gritted molded open-grid grating combines three different attributes: gritted surface, molded construction, and open-grid configuration. The phrase still does not establish dimensions, load capacity, span, material system, or tested slip performance.

How to Build a Complete FRP Grating Description

A useful product description combines attributes from separate classification dimensions:

[Construction] + [Top configuration] + [Measured opening] + [Surface] + [Panel and support requirements]

For example, gritted molded open-grid fiberglass grating identifies a surface, a construction, a top configuration, and a material family. The measured opening, panel dimensions, clear span, loads, service environment, and required documentation still need to be added.

Phrase element	Classification dimension	What it contributes
Gritted	Surface	Identifies the stated top finish
Molded	Construction	Identifies how the grid is formed
Open-grid	Top configuration	Identifies that the panel has through-openings
Fiberglass	Material family	Identifies glass-fiber-reinforced polymer terminology

This is a description framework, not a product availability matrix. Each combination must be checked against current documentation.

Molded FRP Grating

Molded FRP grating is formed as an integral grid panel in a mold. Glass reinforcement and a polymer matrix are placed and cured to create the grid structure. TWI describes GRP molding as a process in which glass reinforcement is arranged in a mold and resin is added and cured.[1]

The construction label molded does not identify one universal mesh, panel size, surface, load rating, or material formulation. For a project review, record the panel layout, supports, clear spans, openings, surface requirement, service environment, and acceptance documents, then compare those inputs with product-specific data.

Pultruded FRP Grating

Pultruded FRP grating is assembled from load-bearing profiles produced by pultrusion and connected with cross members. In pultrusion, continuous reinforcement is pulled through resin and a forming die to produce profiles with a consistent cross-section.[1]

Because the assembled panel has an identifiable bearing direction, the panel layout and support drawing need to show that direction clearly. The word pultruded alone does not establish the permitted span, load, deflection, surface, fastening, or material system.

This page identifies the two construction categories without assigning a universal winner. For a focused review of their structural differences and selection evidence, read pultruded grating vs molded FRP grating.

Open-Grid, Covered, and Solid-Top Configurations

Open-grid grating has visible openings through the panel. Those openings can support drainage, airflow, light transmission, or the passage of material smaller than the opening, but the actual result depends on the opening geometry and operating conditions.

The terms covered grating and solid-top grating describe a more continuous top configuration. They do not always identify the same construction. A cover may be a separate component attached to a grid, while a supplier may use solid-top for a different integrated or assembled product. Before treating the terms as equivalent, request a cross-section or drawing that shows:

• the base grating construction;
• the top component and how it is formed or attached;
• panel and opening dimensions;
• edge and support details;
• the surface finish;
• product-specific load and acceptance documentation.

Our fiberglass grating information lists solid-top as a public top option. That listing does not mean every construction, size, material system, or surface combination is available. The exact configuration needs to be confirmed during product review.

Open Mesh and Narrower-Opening Grating

Opening terminology is not a substitute for dimensions. Open mesh generally describes a grid with through-openings, while terms such as narrow opening, mini mesh, or micro mesh may be used for smaller openings. The boundary between these labels can vary by supplier and product line.

Specify the opening requirement with measurable inputs instead of relying on the category name. Record the maximum permitted opening, any object-passage or access criterion, drainage or ventilation objective, panel layout, and applicable project rule. Then verify the proposed mesh against a product drawing or data sheet.

Narrow-opening, mini-mesh, and micro-mesh are explained here as market terminology. Send the required opening dimensions and project criteria so they can be compared with current product options during review.

Smooth, Concave, and Gritted Surfaces

Surface terms describe the top finish, not the basic grating construction. Our listed surface options include smooth, concave, and gritted finishes for selected fiberglass grating products. Available combinations depend on the construction, dimensions, and current product specification.

Surface term	Basic description	Inputs and evidence to review
Smooth	A comparatively smooth top finish	Intended traffic, housekeeping, operating environment, and any required surface test
Concave	A top profile with a concave form	Actual profile drawing, operating conditions, and any required test criterion
Gritted	A surface that incorporates or carries abrasive grit	Grit construction, applicable test data, wear conditions, cleaning method, and available product combinations

Solid-top is treated here as a top configuration, not as a walking-surface finish. A solid-top panel still needs a separate description of its actual surface finish. If slip performance is a project requirement, define the test method, condition, acceptance value, and documentation required for the exact product.

FRP Grating Type Selection Matrix

Use the following sequence to turn general type labels into a reviewable requirement.

Decision step	Project input	Verification action	Required output
1. Define the construction question	Existing specification, layout, support direction, and whether molded or pultruded is already required	Compare the construction description with the drawing and product data	Agreed construction category and bearing direction where applicable
2. Define the top configuration	Drainage, passage, containment, access, and housekeeping needs	Review open-grid, covered, or solid-top cross-sections	Named configuration with a drawing reference
3. Define the openings	Maximum opening, object-passage criterion, drainage or ventilation need	Check actual opening dimensions and open area in product documentation	Approved mesh or opening requirement
4. Define the surface	Traffic, contamination, cleaning, wear, and any safety criterion	Match the proposed surface with the specified test and operating condition	Surface description and acceptance evidence
5. Complete the structural review	Support layout, clear span, loads, deflection or other acceptance criteria, and cutouts	Use product-specific load/span information and the required design approval	Approved panel layout and product selection
6. Complete the commercial package	Quantity, destination, required submittals, and requested delivery terms	Align the drawing, quotation, and purchase order	Consistent purchase description and document list

The minimum output is not simply “molded” or “pultruded.” It is a traceable description that identifies construction, configuration, openings, surface, layout, support conditions, performance criteria, and required documentation.

Common Classification Mistakes

Avoid these errors when reading catalogs or preparing an RFQ:

• Treating surface as construction. Gritted and concave describe the top surface; they do not replace molded or pultruded as the construction label.
• Treating covered and solid-top as universal synonyms. Ask for a section drawing and attachment detail.
• Treating a mesh name as a dimension. Record actual opening dimensions and the project criterion they must satisfy.
• Assuming all combinations are available. Verify the product matrix instead of combining catalog terms freely.
• Selecting from the type name alone. Load, span, supports, environment, surface criteria, and acceptance documents remain separate inputs.

Discuss an FRP Grating Requirement

Review our molded and pultruded fiberglass grating options. For a project discussion, send the application, panel layout, support arrangement, clear spans, load and acceptance requirements, opening or top-configuration requirement, surface requirement, service environment, quantity, destination, and required documents. Product-specific combinations, dimensions, availability, documentation, and commercial terms can then be confirmed during review and quotation.

Reference

1. TWI, “What are Glass Reinforced Plastic (GRP) Composites?” https://www.twi-global.com/technical-knowledge/faqs/what-are-glass-reinforced-plastic-grp-composites