Playground Surfacing Depth Calculator (BS EN 1177): Critical Fall Height
Two tools in one, both to BS EN 1177:2018. Use the Depth tab to find the minimum surfacing depth for your play equipment's fall height, or the CFH tab to check what fall height an existing surface and depth is safe for. The installed surface must always carry its own test certificate.
🔧 Playground Surfacing Calculator
BS EN 1177:2018 · indicative planning guidance. Confirm the final surface and depth against the product’s own test certificate.
How the calculator works
BS EN 1177:2018 is the UK and European standard for impact-attenuating playground surfacing. A surface is drop-tested to establish its Critical Fall Height — the greatest height from which a head-first fall onto it keeps the Head Injury Criterion (HIC) below 1000. The rule is simple: the surface’s rated CFH must be equal to or greater than the equipment’s free height of fall. How much depth that takes depends on the surface — loose fills need the most, engineered tiles and wet pour the least.
Do you actually need safety surfacing?
Not every play feature legally needs certified impact-attenuating surfacing — but most do. Under BS EN 1176, impact-attenuating surfacing to BS EN 1177:2018 is required across the whole impact area wherever equipment has a free height of fall greater than 600 mm.
It is also required at any height under equipment that puts the body into forced movement — swings, slides, cableways, roundabouts and seesaws — because a child can be thrown clear of the equipment rather than simply dropping.
Indicative depths by surface type
| Surface | Depth / thickness | Approx. max CFH |
|---|---|---|
| Loose rubber mulch / chippings | 200 mm | up to ~2.0 m* |
| Loose rubber mulch / chippings | 300 mm | up to ~3.0 m* |
| Loose bark / wood chip | 300 mm | up to ~3.0 m |
| Rubber safety tiles | 40 mm | up to ~1.0 m |
| Rubber safety tiles | 50 mm | up to ~1.5 m |
| Rubber safety tiles | 65 mm | up to ~2.0 m |
| Rubber safety tiles | 80 mm | up to ~3.0 m |
| Rubber grass mats | standard mat | up to ~1.3 m |
| Wet pour rubber | set by system certificate | increases with base depth |
| Loose sand (washed) / pea gravel | 300 mm | up to ~3.0 m |
| Grass / topsoil (established turf) | established sward | up to ~1.0 m only |
| Hard surfaces (concrete, tarmac, paving) | any | Not acceptable above 0.6 m |
*Loose rubber performance is product-specific — always confirm the depth against the individual product’s BS EN 1177 test certificate. Tile thicknesses are typical certified ratings and vary by manufacturer. Loose-fill figures for bark, wood chip, sand and gravel (200 mm → 2 m, 300 mm → 3 m) are the tested baseline values in BS EN 1177:2018; the standard requires an extra ~100 mm above the tested minimum to allow for displacement and compaction, so a 200 mm rating is installed at roughly 300 mm. Grass and topsoil lose their attenuation as they wear, compact or dry out, so they are only counted up to about 1.0 m.
What is free height of fall?
The free height of fall is the greatest vertical distance from the clearly intended body support — the highest point a child stands on, sits on or grips — to the surface below. For a platform it is the platform height; for a swing it is measured from the seat at rest, per BS EN 1176. If in doubt, measure to the highest reasonably accessible point and round up.
How far must the surfacing extend?
Getting the depth right is only half the job — the surfacing has to cover the whole impact area, not just the patch directly beneath the equipment. A child rarely falls straight down.
- For a free height of fall up to 1.5 m, the impact area extends a minimum of 1.5 m in every direction from the equipment.
- For a fall height above 1.5 m, the minimum extent grows with height: (⅔ × free height of fall) + 0.5 m. A 3 m platform, for example, needs surfacing reaching about 2.5 m out.
- Swings and slides need more. Swings throw a child forwards and backwards, so the impact area runs well beyond the arc; slides need a clear, surfaced run-off at the foot of the chute. Follow the equipment manufacturer’s stated impact area.
Work out the surfaced area first, then use our rubber chippings coverage calculator to turn that area and depth into the number of bags you need.
Inspecting and maintaining your surfacing
Certified surfacing only stays compliant if it is maintained. BS EN 1176 sets out three levels of inspection:
- Routine visual checks — weekly to monthly depending on how heavily the area is used; look for displacement, contamination and sharp objects.
- Operational inspections — every 1–3 months, checking wear and depth, especially under swings and at slide exits where loose fill scatters fastest.
- Annual main inspection — a thorough yearly assessment, ideally by a competent inspector registered with the RPII (Register of Play Inspectors International).
With loose fills, rake the surface level and top up regularly so it never drops below its certified depth — the wear points under swing seats and slide exits need attention first.
Frequently asked questions
Critical Fall Height (CFH) is the maximum height from which a fall onto a surface keeps the impact within safe limits under BS EN 1177:2018. It depends on the surface type and its depth or thickness, and it must be at least as high as your equipment’s free height of fall.
As a loose-fill safety surface, rubber mulch typically needs around 200–300 mm depending on the fall height — about 300 mm for a 3 m fall — and should be laid 10–15% deeper so it stays compliant as it settles. Shallower depths (25–100 mm) suit paths and landscaping, not fall protection.
No. Decorative rubber chippings are not automatically a substitute for certified impact-attenuating surfacing. For any fall-from-height area, choose a product with a BS EN 1177:2018 test certificate stating its rated CFH, and install it to the certified depth.
Measure the vertical distance from the highest point a child stands, sits or grips down to the surface. For platforms use the platform height; for swings measure from the seat at rest. When unsure, measure to the highest reasonably accessible point and round up.
Loose fills settle, compact and displace with use, so lay them 10–15% deeper than the target and top up regularly to maintain the certified depth. Bark and wood chip also decompose and need more frequent replacement than rubber.
Yes. Swings and slides create forced movement, so BS EN 1176 requires impact-attenuating surfacing beneath and around them at any fall height — not just above 600 mm. The surfaced impact area also has to extend well beyond the equipment: past the full swing arc, and along the run-off at the foot of a slide.
At least 1.5 m in every direction for fall heights up to 1.5 m. Above that, the minimum extent is (two-thirds × free height of fall) + 0.5 m, so a 3 m fall needs roughly 2.5 m of surfacing all round. Swings and slides need extra clearance in the direction of travel — always follow the equipment manufacturer’s impact-area figures.
Sources
BS EN 1177:2018 — Impact Attenuating Playground Surfacing: Determination of Critical Fall Height. Equipment, the 600 mm surfacing threshold, impact-area extent and inspection regime are covered by BS EN 1176. Loose-fill baseline depths (200 mm → 2 m, 300 mm → 3 m) and the ~100 mm displacement allowance are per BS EN 1177:2018 / BS EN 1176 tested figures; grass/topsoil counted to ~1.0 m. Tile and loose-fill ranges are typical certified values — confirm against each product’s own test certificate. Inspection tiers per BS EN 1176-7; competent inspectors via the RPII.
Playground Rubber Chippings, Delivered
Recycled rubber chippings and coloured rubber mulch in bulk bags, with UK delivery. Certified impact-absorbing surfacing for play areas.
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