Safety in practice
Impact attenuating surfacing: free height of fall, depth and the impact area
Above 600 mm free height of fall the ground has to absorb impact. The depths for loose fill, how the impact area is measured, and the faults that come back.
Short answer
Where the free height of fall is above 600 mm, and wherever the equipment forces movement whatever the height, the ground below has to be impact attenuating. For loose fill such as sand, wood chips and bark, EN 1176-1 gives 200 mm up to a 2 m fall and 300 mm up to 3 m — plus 100 mm extra, because loose material is displaced in use. The largest free height of fall is 3000 mm. Concrete, stone and asphalt never count.
The surfacing is the part of a playground that draws the least attention and decides the most. The equipment is what people see; the ground underneath decides whether a fall becomes a grazed knee or a trip to hospital. It is also the part that decays fastest and is forgotten most often, because sand and wood chips disappear a little at a time without anybody noticing.
Almost every English-language page on this subject is written by somebody who sells surfacing. They are usually well informed and they are never disinterested. This one sells software instead, which is its own bias, but not one that is served by telling you to lay more rubber.
When does the ground have to absorb impact?
The rule has two parts, and the second is the one that gets forgotten: the surface has to be impact attenuating where the free height of fall is above 600 mm, and also wherever the equipment forces movement — a swing, a cableway, a roundabout — whatever the height. The free height of fall is the greatest vertical distance from the point where a child's weight rests on the equipment — the standing surface, the seat, the grip they are hanging from — down to the ground.
The second limit is absolute. The largest free height of fall is 3000 mm. Above that the equipment does not conform to EN 1176, however good the surface below it is.
Depths for loose fill: sand, wood chips, bark and gravel
Loose fill is the most common solution and the cheapest to get wrong. The depths are in EN 1176-1 — EN 1177 is the test standard that says how impact attenuation is measured and gives no depths itself, which is a distinction worth keeping straight when somebody quotes a figure at you.
| Free height of fall | Depth | With the allowance for displacement |
|---|---|---|
| Up to 2 m | 200 mm | 200 + 100 = 300 mm laid |
| Up to 3 m | 300 mm | 300 + 100 = 400 mm laid |
The extra 100 millimetres are not a safety margin — they are a precondition. Loose material is displaced when children use the equipment: sand is kicked out from under the swing, chips are pushed away at the foot of the slide. Lay only the nominal depth and the surface is already too thin in its first season.
The material itself matters too. Sand should be washed and free of fine particles — ordinary fill sand compacts and loses its attenuation. Wood chips and bark need a particle size the supplier can document against EN 1177, and the material is replaced once it has broken down into compost. If you cannot get documentation for the material, you cannot document that the surface absorbs impact either.
The impact area: how much ground has to be covered
The surface has to cover the whole impact area, not only the ground directly beneath the equipment. The rule of thumb for how far it extends is two thirds of the free height of fall plus 0.5 m, and never less than 1.5 m. With a fall height of 1.8 m that gives 2/3 × 1.8 m + 0.5 m = 1.7 m, which is more than the minimum, so 1.7 m is what applies.
For equipment with forced movement — swings, roundabouts, cableways — the areas are larger and shaped differently, because the child leaves the equipment while moving. A swing needs clear ground in front of and behind it in the direction of swing. A nest swing rotates as well, so the clear ground has to go all the way round. Where two pieces of equipment have overlapping impact areas, it is the outer edges that count.
HIC and critical fall height: what the numbers mean
Manufactured surfaces — rubber tiles, poured rubber, artificial grass over a pad — carry a critical fall height: the greatest fall height the material has been tested for. The test method in EN 1177 drops a headform onto the surface and measures two things at once: the peak deceleration, which must stay at or below 200 g, and the HIC value (Head Injury Criterion), which must stay at or below 1000. A surface has to pass both. Below those limits, the fall counts as one that is not expected to cause a life-threatening head injury.
For you as the owner that turns into one practical rule: the critical fall height of the surface has to be at least as high as the free height of fall of the equipment above it. Tiles rated to 1.5 m under a climbing frame with a 2.2 m fall height are too weak, however neat they look. Ask for the product documentation and keep it with the rest of the site's records.
Seven faults you can find yourself
- The hollow under the swing. Where children brake, the surface goes first. Measure there, not at the edge.
- Chips pushed away at the foot of the slide. The same fault, a different place, just as common.
- Compacted material. Bark that has been trodden flat or frozen solid absorbs impact about as well as asphalt does.
- Exposed foundations. When the surfacing is carried away, the concrete appears — often with a sharp edge.
- An edging that now sits higher than the surface. The kerb that was meant to hold the fill in has become a hard object to land on.
- Water and ice. No drainage in the impact area means standing water in autumn and ice in winter.
- Broken-down bark. When it smells of soil it is soil, and soil is not impact attenuating surfacing.
Measure it, do not look at it
Push a stick or a folding rule in at several points in the impact area — under the swing, at the foot of the slide, in the landing areas — and measure to firm ground, not to the fluffy top layer. Write the number down instead of ticking “in order”.
Then you have two things at once: a surface that absorbs impact, and a series of numbers that shows how fast the material is disappearing, and therefore when the next top-up falls due. Put the measurement in as a fixed point on the operational inspection; see the checklist.
Questions and answers
How deep should playground surfacing be?
For loose fill such as sand, wood chips, bark and gravel, EN 1176-1 gives 200 mm for fall heights up to 2 m and 300 mm up to 3 m. Add 100 mm on top of that, because loose material is displaced in use — so 300 mm and 400 mm as laid. Measure to firm ground, at the places where children brake.
What is critical fall height?
It is the greatest fall height a surface has been tested for under EN 1177. The test drops an instrumented head form and measures the HIC value; the limit is a HIC of 1000. The critical fall height of your surface has to be at least as high as the free height of fall of the equipment standing on it.
Does grass count as impact attenuating surfacing?
It depends on the fall height, and it is hard to document. Natural, well-kept grass can work under low fall heights, but it loses attenuation as it dries out, compacts, or is worn to bare soil under a well-used piece of equipment. EN 1176-1 lists grass and topsoil as usable up to a fall of about a metre without testing; above that you need a surface whose performance you can show, and grass rarely comes with documentation.
Does the extra 100 mm apply to rubber tiles as well?
No. The allowance is for loose materials, which are displaced in use. A tile stays where it is laid and is documented instead by its critical fall height, which has to be at least as high as the free height of fall of the equipment above it.
How often does loose fill need topping up?
As often as the measurement says. On a well-used playground once a year is a normal starting point, and the hollow under the swing usually needs raking back considerably more often than that. This is exactly why depth belongs on the operational inspection and not only in the annual main inspection.
Sources
- EN 1176 and EN 1177 – CEN/TC 136 Sports, playground and other recreational facilities and equipment (CEN-CENELEC)
- CEN-CENELEC: European Standards, and how members adopt them nationally
This article is written by The Lekko editorial team and gives a practical account of the requirements. It does not reproduce the standards EN 1176 and EN 1177, and it does not replace the annual main inspection by a competent person. If you are unsure what applies to your playground, ask a competent person or the relevant authority in your own country.
Less fuss. Lekko remembers.
Ready-made checklists built from EN 1176 and EN 1177, a reminder before every inspection, and a report you can hand over in one click.