Playground Surfacing Depth Calculator (BS EN 1177): Critical Fall Height
Enter the free height of fall of your play equipment — the greatest height a child can fall from — and this calculator shows the minimum surfacing depth each surface type needs to meet that fall height under BS EN 1177:2018. Use it to plan and budget alongside our playground surfacing guide and rubber chippings coverage calculator. The installed surface must always carry its own test certificate.
🔧 Critical Fall Height → Required Depth
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.
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 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 wood-chip figure (300 mm → 3 m) is per BS EN 1177:2018 tested values.
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.
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. Use our coverage calculator to turn the required depth into bulk-bag quantities.
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. See how long rubber chippings last.
Sources
BS EN 1177:2018 — Impact Attenuating Playground Surfacing: Determination of Critical Fall Height. Equipment is covered by BS EN 1176. Loose-fill wood-chip depth (300 mm → 3 m CFH) per BS EN 1177:2018 tested figures. Tile and loose-fill ranges are typical certified values; confirm against each product’s own test certificate.
Playground Rubber Chippings, Delivered
Recycled rubber chippings and coloured rubber mulch in bulk bags, with UK delivery. Work out quantities with the coverage calculator, then order the right amount.
Browse Rubber Chippings → Coverage Calculator →Related guides
- Playground surfacing: the complete UK guide — types, BS EN 1177 and 2026 costs.
- Rubber chippings coverage calculator — how many bulk bags you need for your area and depth.
- How to prepare and install rubber chippings — ground prep, membrane and edging.
- Rubber chippings vs bark for play areas — which to choose and why.
- How long do rubber chippings last? — lifespan and top-up guidance.
- Rubber mulch cost UK — what rubber chippings cost in 2026.