Safety & standards
Critical Fall Height: Playground Surface Guide
What critical fall height means under EN 1177, how to match it to your equipment fall zones, and how to specify a compliant surface depth.
If you’ve ever received a specification document for a playground surface, you’ll have seen the phrase Critical Fall Height (CFH) — usually followed by a number in metres. That number is arguably the single most important figure in playground safety.
Get it right and your surface meets EN 1177. Get it wrong and you have a compliant-looking playground with a surface that doesn’t protect a falling child.
This guide explains what CFH means, how it’s calculated from your equipment, and what it means when you’re choosing or specifying a surface.
What Is Critical Fall Height?
Critical Fall Height is the maximum height from which a child can fall onto a playground surface without the impact force exceeding the EN 1177 thresholds:
- HIC ≤ 1000 (Head Injury Criterion — a composite measure of impact severity over time)
- g_max ≤ 200 g (peak deceleration at the point of impact)
These thresholds are set at the level below which the statistical risk of a life-threatening head injury is considered acceptable. They are not “safe” — they are the minimum acceptable limit.
A surface’s CFH is established by lab testing: a weighted headform is dropped from increasing heights onto the surface until one of the thresholds is breached. The last height at which both values were within limits is the certified CFH.
Where the CFH Requirement Comes From: EN 1176
The surface CFH requirement for any given playground is not arbitrary — it is derived directly from the play equipment, governed by EN 1176 (Playground equipment and surfacing — Part 1: General safety requirements).
EN 1176 defines the maximum free height of fall for each piece of equipment. The surface must be certified to a CFH at least equal to the equipment’s maximum free height of fall.
Common equipment heights:
| Equipment type | Typical max free fall height |
|---|---|
| Toddler slide | 0.6–1.0 m |
| Standard junior swing (seat height) | 0.6 m |
| Junior climbing frame | 1.0–2.0 m |
| Rope pyramid / net structure | 2.0–3.0 m |
| Fireman’s pole (height of platform) | 1.0–2.5 m |
| Adventure/senior climbing frame | 2.0–3.0 m |
| Zip wire (height above ground at mid-point) | 0.6–1.5 m |
Worked example:
Your installation includes a climbing frame with an accessible platform at 2.4 m. EN 1176 rates this equipment at a maximum free fall height of 2.4 m. Your surface must therefore be certified to EN 1177 at a CFH of at least 2.4 m in the configuration you’re installing.
If your chosen wet-pour EPDM is only certified to 2.0 m at 80 mm depth, you either need:
- A thicker installation (re-tested at the new depth), or
- A different surface product with a higher CFH at your available thickness.
CFH Varies by Installation Depth and Configuration
This is where many procurement mistakes happen.
A surface product’s CFH is not a fixed property of the material — it is a property of the full system as installed. Change the depth, the subbase, or the pad specification and you change the CFH. The EN 1177 certificate is only valid for the exact configuration tested.
Loose-fill surfaces
| Material | 200 mm depth | 300 mm depth |
|---|---|---|
| Sand | ~0.5 m | ~0.8 m |
| Bark chip (graded) | ~1.5 m | ~2.5 m |
| Rubber crumb (loose) | ~1.5 m | ~2.0 m |
Loose-fill CFH degrades during use as material is kicked or thrown out of the fall zone. The certified depth must be maintained at all times for the certification to apply.
Bound surfaces (indicative — always refer to product test report)
| Product type | 40 mm | 60 mm | 80 mm | 100 mm |
|---|---|---|---|---|
| Standard wet-pour EPDM | ~1.0 m | ~1.5 m | ~2.0 m | ~2.5 m |
| Rubber tiles | ~0.8 m | ~1.2 m | — | — |
| Tufted grass + 50 mm EPE pad | — | ~1.5 m | — | — |
| Tufted grass + 70 mm foam pad | — | — | ~2.5 m | — |
These are illustrative ranges. Always request the test report for the specific product you are purchasing.
The Surfacing Zone: How Far from the Equipment Must the CFH Apply?
EN 1176 defines surfacing zones — the area around each piece of equipment that must be covered by impact-attenuating surfacing at the required CFH. The zone extends beyond the physical footprint of the equipment.
Key rules:
- For swings: the surfacing zone extends forward and backward from the swing seat by twice the height of the suspension point.
- For slides: the zone extends from the exit point to the point where a falling child would land.
- For climbing equipment: a radius around the equipment, determined by the fall-height profile.
Surfacing zones are calculated per piece of equipment and shown in the EN 1176 product documentation. Where surfacing zones from adjacent pieces of equipment overlap, the higher CFH requirement applies across the entire overlap area.
A common error: surfacing the main fall zones correctly, then using a lower-spec material at the edges of the zone or between pieces of equipment. If a child falls at that point, the zone boundary is not a meaningful protection.
CFH and Accessibility
EN 1177 CFH requirements do not conflict with accessibility. Bound surfaces (wet-pour, rubber tiles, tufted grass on a pad) that are designed to achieve a specific CFH are also fully accessible to wheelchair users and pushchairs — unlike loose-fill.
For inclusive playground design, a surface that achieves the required CFH while remaining accessible is always preferable to a loose-fill surface that achieves the CFH technically but excludes mobility-impaired users.
Maintaining CFH After Installation
For bound surfaces: the CFH is durable, but can degrade if:
- The surface is physically damaged (cuts, gouges, delamination) — inspect regularly.
- The subbase shifts or becomes waterlogged — check drainage annually.
- The surface is repaired with materials from a different batch or supplier — always use the original material or a tested equivalent.
For loose-fill: the CFH degrades every day the playground is in use. Monthly depth checks and top-up schedules are required. Many public-sector operators underestimate this cost when initially specifying loose-fill.
Documenting CFH for Operators and Inspectors
For each playground installation, the handover package should include:
- EN 1177 lab test report for the surface at the installed configuration.
- Post-installation field test report confirming the installed surface meets the required CFH.
- Equipment CFH mapping — a plan showing each piece of equipment, its maximum free fall height, the required CFH, and the surface zone.
- Maintenance schedule specifying the inspection frequency, top-up requirements (loose-fill), and the trigger conditions for re-testing.
This package is what protects the operator from liability following an incident, and what an EN 1176/EN 1177 inspector will ask for on a site audit.