One of the most common questions people ask when specifying GRP grating is simply: what thickness do I actually need?
In practice, there is no single answer because the correct panel depth depends entirely on the span, loading, support spacing, traffic type and the environment the grating will be installed in.
Choosing the wrong thickness can lead to excessive deflection, unnecessary cost or an over-engineered installation. That is why GRP grating should always be selected based on the actual application rather than simply choosing the thickest panel available.
Across most industrial projects, 25mm, 38mm and 50mm remain the most commonly specified panel depths, with each suited to different structural requirements.
25mm GRP Grating
25mm moulded grating is generally used for lighter-duty pedestrian applications where support centres are relatively close together.
It is commonly specified for plant walkways, service risers, access flooring and low-span maintenance platforms.
Where spans are limited and loading is relatively light, 25mm panels often provide a practical and economical solution without unnecessary weight or material cost.
That said, thinner panels can become unsuitable quite quickly once spans increase or heavier loads are introduced. Excessive deflection is usually the first issue rather than outright structural failure.
For this reason, 25mm grating is rarely used for long-span walkways, heavy-duty platforms or areas with regular equipment traffic.
38mm GRP Grating
38mm grating is probably the most widely used specification across general industrial environments.
It offers a good balance between span capability, stiffness, weight and installation practicality.
You will commonly see 38mm moulded grating used on industrial walkways, rooftop access systems, wastewater treatment plants, chemical processing facilities, offshore environments and elevated platforms.
In many situations, 38mm panels provide enough rigidity for pedestrian traffic while still remaining relatively lightweight and easy to install.
This is often the standard specification contractors expect to see on industrial access projects because it suits such a broad range of applications.
50mm GRP Grating
50mm grating is typically specified where greater span performance or higher load capacity is required.
The increased panel depth improves stiffness and reduces deflection over larger support centres, making it more suitable for heavy-duty access platforms, bridge walkways, service gantries, equipment zones and higher-load industrial flooring.
On some projects, 50mm grating may also be used where steelwork support spacing cannot easily be reduced and the grating itself needs to carry greater structural demand.
Although deeper panels provide higher load capability, they also increase overall system depth and weight, so there is little benefit in over-specifying them where lighter-duty systems would perform adequately.
Why Span Matters More Than Thickness Alone
One mistake people often make is assuming thickness alone determines strength.
In reality, support spacing is just as important.
A 38mm panel spanning a short distance may perform better than a thicker panel installed over an excessive unsupported span. This is why proper load and deflection calculations matter when selecting any GRP flooring system.
The type of load also changes the specification significantly.
Pedestrian traffic behaves very differently to pallet truck loading, equipment access, concentrated point loads or maintenance plant traffic.
Two projects using the same grating depth may therefore require completely different support arrangements depending on how the flooring will actually be used.
Moulded vs Pultruded Grating Thickness
Thickness selection also depends on whether the system is moulded or pultruded.
Moulded grating distributes load in two directions through its interwoven mesh structure, making it versatile for general access flooring and industrial walkways.
Pultruded grating behaves differently because the primary load-bearing bars run in one direction. This gives it significantly greater span capability and stiffness along the bearing direction.
Because of this, pultruded systems are often used where longer unsupported spans are required, structural loading is higher or deflection control is critical.
In many heavy-duty applications, a pultruded system may achieve the required span more efficiently than simply increasing the thickness of moulded grating.
Rooftop Walkways & Access Systems
Rooftop projects often introduce slightly different considerations.
Loading may be relatively light compared to heavy industrial platforms, but factors such as deflection, underfoot feel, heel safety and support spacing become more noticeable in daily use.
This is one reason mini mesh GRP grating is commonly specified for rooftop walkways. The smaller aperture creates a more comfortable walking surface while still maintaining drainage and slip resistance.
Grey 38mm mini mesh panels are now regularly used across commercial rooftops, particularly around HVAC systems and maintenance access routes.
Why Over-Specifying Is Not Always Better
There is a tendency on some projects to assume heavier grating automatically means better performance.
In reality, unnecessary panel depth can increase costs, add installation weight, complicate support details and create awkward interface levels with surrounding structures.
The aim should always be to specify the correct panel for the actual span and loading requirements rather than simply selecting the heaviest option available.
Well-designed GRP access systems balance structural performance, weight, installation efficiency and long-term durability.
Selecting The Correct GRP Grating Specification
The most suitable grating thickness depends on the complete application, not just the product itself.
Factors such as support centres, load requirements, environment, traffic type, resin system and access frequency all influence the final specification.
