SAFETY SURFACING • THICKNESS, TESTING & SPECIFICATION
Choose artificial grass shock-pad thickness from the tested performance of the complete surfacing system and the requirements of the play area—not from thickness alone. A 25 mm or 45 mm pad does not have one universal Critical Fall Height that applies beneath every turf, on every base.
This guide explains what those thickness options can and cannot tell you, which evidence to ask for and how to avoid buying a surface that feels soft but has not been shown suitable for its intended use.
What Is Critical Fall Height?
Critical Fall Height, or CFH, describes the performance established by impact testing of a surfacing system. It is not a promise that a child can fall from that height without injury, nor a complete safety assessment of the playground.
BSI’s explanation of BS EN 1177 distinguishes testing used to establish CFH from on-site testing used to check the performance of a particular installed surface. The relevant test evidence matters more than a general claim that a pad is “safety compliant”.
For the wider concept, see our Critical Fall Height guide. Here, the focus is selecting the underlay within the proposed build-up.
25 mm vs 45 mm Shock Pads: What Can You Compare?
| Question | 25 mm Option | 45 mm Option |
|---|---|---|
| Nominal pad depth | 25 mm | 45 mm |
| Automatic CFH rating? | No. Check the report for the named system. | No. Greater depth is not a transferable certificate. |
| When could it be appropriate? | Where the documented performance meets the project’s requirements. | Where the documented performance meets the project’s requirements. |
| What else affects the decision? | Pad material, turf, substrate, installation detail and intended use. | The same factors, plus the effect of the greater build-up on finished levels. |
| Can it be substituted without checking? | Do not assume it is equivalent to another 25 mm product. | Do not assume it is equivalent to another 45 mm product. |
This is deliberately not a universal thickness-to-fall-height conversion table. If a supplier quotes a CFH value, ask which pad, turf, infill and supporting construction that result applies to.
When Might a 25 mm Shock Pad Be Suitable?
A 25 mm option may be suitable where its documented system performance meets the assessed requirements. It should not be selected simply because the site is a school, nursery or small play area.
Ask what equipment is present, what the relevant fall-height and impact-area requirements are, and whether the proposed build-up matches the evidence. A lower-profile product may help with finished levels, but that convenience cannot replace the performance check.
When Might a 45 mm Shock Pad Be Suitable?
A thicker option may be part of the appropriate solution, but “45 mm” is not a universal requirement for climbing frames, early-years areas or SEND settings. Those settings do not all have the same equipment, use or design requirements.
Review the named system, its tested performance, accessibility, surface stability and the way it meets surrounding areas. A thicker pad also changes the build-up, so edges, thresholds and transitions need planning.
How Do the Standards Fit Into the Decision?
BS EN 1177 concerns impact testing of surfacing. The equipment, layout and relevant impact areas also need assessment against the applicable playground requirements, including BS EN 1176 where relevant. A test report is evidence for a particular system or test condition, not a blanket legal sign-off for an entire site.
RoSPA Play Safety’s surfacing guidance recommends obtaining appropriate test evidence and written assurances from suppliers, and recognises the role of on-site testing. Use a competent playground designer or inspector to establish the requirements for your project.
Check the applicable edition and project requirements with the person specifying or inspecting the installation. Do not rely on an old product leaflet or a generic web table as the final specification.
What Should You Request Before Approving a Shock-Pad System?
The Documentation Checklist
- Equipment and use: the relevant free-fall heights, impact areas, age group and intended activities.
- Named components: the exact pad, turf and any infill—not just “25 mm underlay and grass”.
- Supporting construction: the substrate, base and installation conditions to which the evidence applies.
- Test evidence: the applicable report, identified system and documented performance.
- Installation details: edges, joins, transitions, drainage and any changes in level.
- Inspection and handover: required checks, maintenance instructions, records and warranty scope.
If any part of the quoted build-up differs from the tested system, ask the supplier or competent specifier to confirm whether the evidence still applies. Do not make that assumption from appearance or feel.
Do Gardens, Playgrounds and Sports Pitches Need the Same Pad?
No. General garden comfort, impact protection beneath play equipment and sports performance are different purposes. A soft domestic lawn is not automatically a certified playground safety surface.
Sports surfaces may need sport-specific testing and performance requirements; playground CFH should not be treated as the only measure of suitability for a football, rugby or multi-use pitch.
Compare when an underlay is needed with the requirements of your actual setting. For a playground project, our safety flooring and shock-pad service is the appropriate route to discuss the complete installation.
Installation, Inspection and Ongoing Care
Keep the finished surface and its transitions in good condition. Lifting edges, open joins, damaged turf or changes in the supporting base need assessment; an original test report does not make deterioration irrelevant.
Follow the system’s maintenance and inspection requirements, and retain the handover documentation. Where a safety concern is identified, manage access to the affected area until a competent person has assessed the next step.
The work should be planned around the site’s use and the relevant inspection process—not around an assumed fixed lifespan for every pad.
FAQs About Artificial Grass Shock-Pad Thickness
Does a 25 mm pad always provide the same fall protection?
No. The result depends on the named system and applicable test evidence. Thickness alone is not a CFH rating.
Is 45 mm always safer than 25 mm?
You cannot establish overall suitability from thickness alone. Compare documented performance, the intended use and the complete installation.
Can different pad thicknesses be used on one site?
Possibly, where a competent design specifies the relevant systems and transitions. Each area must be assessed for its requirements; changes in level must not create new problems.
Can I put a shock pad over an existing hard surface?
Potentially, if the substrate and whole system are suitable for the intended use. Its condition, drainage, levels and applicable evidence need checking first.
Does thick artificial grass remove the need for a pad?
Do not assume so. The pile height or soft feel of turf is not proof of the required impact performance.
Can an old pad be reused when the turf is replaced?
It needs assessment. Condition, compatibility and the evidence for the proposed replacement system matter; reusing it is not an automatic cost-saving option.
Specify the Whole Safety Surface, Not Just the Pad
Send us the site details, equipment information and any existing plans or inspection requirements. We can discuss the proposed artificial grass and shock-pad build-up, and what evidence is needed.
Updated 10 September 2026.
