There is no single maximum span that applies to all GRP grating.
The distance a panel can span between supports depends on the depth and construction of the grating, the load it needs to carry and the amount of deflection permitted. Increasing the distance between supports generally increases deflection and reduces the load that the grating can accommodate.
This is why GRP grating should not be selected on panel depth alone. A 25mm, 38mm or 50mm panel can perform very differently depending on the clear span and loading applied to it.
What Does Clear Span Mean?
Clear span is the unsupported distance between the structures supporting the GRP grating.
For example, if a panel is supported across two beams, the clear span is the distance the grating has to bridge between those supports. It is this unsupported distance, rather than the overall panel size, that is relevant when looking at load and deflection data.
Reducing the clear span gives the grating more frequent support. Increasing it asks the panel to bridge a greater distance, which has a direct effect on deflection and load capacity.
How Does Span Affect GRP Grating?
The effect can be seen clearly in the load data for standard moulded GRP grating.
Take 38mm GRP grating with a 38 x 38mm mesh as an example. Under a uniformly distributed load of 500kg/m², the recorded deflection is:
- 0.3mm at a 400mm clear span
- 0.6mm at a 500mm clear span
- 1.2mm at a 600mm clear span
- 2.1mm at a 700mm clear span
- 3.4mm at an 800mm clear span
- 5.2mm at a 900mm clear span
- 7.8mm at a 1,000mm clear span
- 11.2mm at a 1,100mm clear span
- 15.8mm at a 1,200mm clear span
The panel has not changed. The applied load has not changed. What has changed is the distance between the supports.
That is why asking how far GRP grating can span without also specifying the load does not give enough information to select a panel.
The complete figures for the different panel depths are available in our GRP grating load tables.
Does Thicker GRP Grating Span Further?
Increasing panel depth can provide greater stiffness and allow the grating to accommodate different combinations of span and load, but depth should still be considered alongside the actual project requirements.
The difference can be demonstrated by comparing the published figures for 25mm, 38mm and 50mm moulded grating.
At a 600mm clear span under a uniformly distributed load of 500kg/m²:
- 25mm GRP grating has a stated deflection of 3.05mm
- 38mm GRP grating has a stated deflection of 1.2mm
- 50mm GRP grating has a stated deflection of 0.7mm
This does not mean that the deepest panel should automatically be specified. If a shallower panel satisfies the required loading, span and deflection criteria, increasing the depth may provide no practical benefit to the project.
Why Deflection Matters
Load capacity is only part of the assessment.
A GRP panel can deflect under load before reaching its maximum stated load capacity. The acceptable amount of movement therefore needs to be considered when selecting the grating and setting the support spacing.
This is particularly relevant on walkways, access platforms and other areas where excessive movement underfoot may be unacceptable even though the load itself is within the capacity of the panel.
The required deflection limit should therefore be established alongside the expected loading rather than treating maximum load as the only selection criterion.
Uniform Loads Are Not the Same as Point Loads
The standard load tables on our website show performance under uniformly distributed loads. This means the load is treated as being spread across the grating rather than concentrated at one small point.
That distinction matters.
Equipment feet, trolley wheels and other concentrated loads apply force differently from a load distributed across the panel. Vehicle wheel loads require particular consideration and should not be assessed simply by taking a total vehicle weight and comparing it with a uniformly distributed load figure.
For applications involving forklift traffic, we supply High Load Capacity GRP grating specifically engineered for higher-load applications. The actual vehicle loading and support arrangement should be reviewed before the grating is selected.
Support Arrangement Is Part of the Grating Design
Sometimes the question is framed as: “Which thickness of GRP grating do I need?”
That can miss an important part of the design.
The position and spacing of the supports underneath the grating can be just as important as the panel depth. Where the required span produces too much deflection, changing the support arrangement may be an option rather than simply moving to a deeper panel.
This becomes particularly relevant when GRP grating is being incorporated into a new access platform, walkway or supporting structure where the support centres can be considered as part of the overall design.
What Information Is Needed to Check a GRP Grating Span?
Before selecting a panel, the important information normally includes:
- the clear span between supports
- the expected load
- whether the load is uniformly distributed or concentrated
- the required or permitted deflection
- the proposed grating depth and mesh
- the existing or proposed support arrangement
- how the grating will be used
Where equipment, trolleys, vehicles or other concentrated loads are involved, details of those loads should also be provided.
So, What Is the Maximum Span for GRP Grating?
The answer depends on what the grating is being asked to support.
Our published data contains figures at clear spans ranging from 300mm up to 1,000mm for 25mm grating, up to 1,400mm for 38mm grating and up to 1,500mm for 50mm grating. These should not be interpreted as universal maximum permissible spans.
The load that can be accommodated changes as the span increases, and the resulting deflection also needs to remain suitable for the application.
For that reason, the correct approach is to start with the required load and available support spacing, then use the load and deflection data to determine which panel arrangement is appropriate.
Our GRP Grating Load Tables provide the full published figures for 25mm, 38mm and 50mm moulded grating.
Need Help Checking a GRP Grating Span?
If you have a required span or loading and are unsure which grating depth is appropriate, send us the dimensions, loading information and details of the supporting structure. Drawings and project information can also be reviewed to help determine a suitable panel and support arrangement.
Contact GRP Grating Systems to discuss the requirements of your project.
GRP Grating Span FAQs
Can GRP grating span be increased by adding more supports?
Adding intermediate supports reduces the clear span that the grating has to bridge. This can reduce deflection and may allow the required loading to be accommodated without changing the grating depth. The complete support arrangement still needs to be suitable for the application.
Does the size of the GRP grating panel determine its span?
No. Panel size and clear span are different measurements. A large panel can be supported at several points, so the important dimension for load assessment is the unsupported distance between those supports.
What happens if my required span falls between the figures in the load table?
Do not assume a load or deflection figure between two published values. Provide the actual span and loading requirements so the application can be checked against the available grating and support arrangement.
Do cut-outs in GRP grating affect the support requirements?
They can. Openings for pipework, equipment or other services can change how a panel is supported, particularly where a cut-out is close to an edge or support. The panel layout and additional support requirements should therefore be considered when openings are required.
Should GRP grating span be checked before the supporting structure is fabricated?
Yes, where possible. Considering the grating load, permitted deflection and support spacing together allows the supporting structure to be arranged around the required panel performance rather than checking the grating after the support positions have already been fixed.
