Last updated October 2026
Critical fall height is the highest fall a surface has been tested to cushion, using the BS EN 1177 test, and it must be at least as high as the free height of fall of the equipment above it. Wetpour reaches 1.5 metres at about 40 to 50 mm thick and 3 metres at 75 to 140 mm, depending on the system, from about £40 to £140 per m2 plus VAT. Always buy against the test certificate, not the thickness.
The same fall height needs very different thicknesses from different systems, which is why two quotes can disagree by millimetres and still both be right.
Swipe the table sideways to see every column.
| Critical fall height needed | RTC Safety Surfaces table | Redlynch Leisure table | Rubberco indicative table |
|---|---|---|---|
| 1.5 m | 50 mm | 50 mm (rated 1.7 m) | 40 mm |
| 2.0 m | 70 mm | 70 mm (rated 2.3 m) | 55 mm |
| 2.5 m | 100 mm (rated 2.6 m) | 80 mm | 65 mm |
| 3.0 m | 130 mm | 140 mm (rated 3.2 m) | 75 mm or more |
| Surface | Published price per m2 | How fall height changes it |
|---|---|---|
| Wetpour, about 100 m2 | £40 to £140 (Redlynch Leisure) | Redlynch lists critical fall height as one of the things that set the depth, and so the price |
| Wetpour, surface only | £29 to £39, excluding base works (Soft Surfaces) | Their figure leaves out the base, which RoSPA puts at 150 mm of MOT Type 1 stone as a minimum |
| Bonded rubber mulch | £40 to £75 (Soft Surfaces, Abacus); real quotes £60.75 and £84.39 (Wickham Market Parish Council, 2021) | Depth rises from about 100 mm at 1.5 m to 250 mm at 3 m (Rubberco, indicative) |
| Play-grade artificial grass | £40 to £60, excluding ground preparation (Redlynch Leisure) | Set by the shock pad under the grass, so check the system’s certificate |
What does critical fall height mean when you are buying a surface?
It is the number on the test certificate that has to beat your tallest piece of equipment. BS EN 1177:2018 sets the test: its first method finds the critical fall height of a product, in a laboratory or on site, which shows the range of equipment it suits. Its second method is a drop test on site, which checks how a surface performs when it is laid or later in its life, but does not set a critical fall height.
Rubberco’s compliance guide puts the pass mark in plain terms: a Head Injury Criterion of 1,000 or less at the equipment’s critical fall height. Ask every installer for the certificate for the exact product and thickness they are quoting.
When does a play area need impact absorbing surfacing?
When a child can fall from 600 mm or more. RoSPA says equipment under 600 mm high need not have a protective surface, though it should still have some cushioning, and that all new equipment should be given an appropriate surface. Northumberland County Council’s play equipment guidance applies the same 600 mm trigger and asks for a test certificate for every impact absorbing surface.
RoSPA does not expect older equipment to be resurfaced at once, so an existing play area is usually brought up to date as the surface wears out or the equipment changes. Our safety surfacing for playgrounds page compares the surfaces that meet the rule.
Is grass good enough under play equipment?
Up to 1.5 metres, often yes. RoSPA’s reading of BS EN 1176-1:2017 is that grass, kept in good condition over 150 mm or more of subsoil, is acceptable for falls of up to 1,500 mm, subject to a risk assessment. It warns that grass hardens in dry spells and frost and wears under swings and slides, and where scuffing keeps happening it suggests a firm surface instead. That is the usual reason a school or parish lays rubber playground flooring or grass mats in the worn patches.
How thick does wetpour need to be?
As thick as its own test certificate says for your fall height, which the table shows can range from 40 mm to 50 mm at 1.5 metres and from 75 mm to 140 mm at 3 metres. The gap comes from different rubber blends and test results, so a thinner quote is not automatically a cheaper or weaker surface. RoSPA advises asking for an independent test report for the specific product and each thickness offered.
The thickness is mostly in the black base layer. In one manufacturer’s mix table, the top coloured layer stays at 15 mm whatever the depth, and only the base gets deeper. More on prices and colours is on our wet pour playground surface page.
How deep should rubber mulch, bark or sand be?
Deeper than wetpour, because loose and bonded fills cushion by depth. Rubberco’s indicative table gives bonded rubber mulch at 100 mm for 1.5 metres rising to 250 mm for 3 metres, and bark at 200 mm rising to 350 mm or more. Northumberland County Council’s guidance sets loose fill at 300 mm minimum, plus 100 mm to allow for it being kicked away. Sand is not recommended above 2 metres in Rubberco’s table.
Bonded mulch holds its depth; loose bark and sand need raking back into place. See playground rubber mulch for prices.
How does fall height change the price?
Taller equipment needs a deeper base, and the base is where the material goes. One manufacturer’s mix table shows a 100 mm wetpour using about four times the base rubber of a 35 mm one. A surfacing maker, Conica, makes the same point from the design side: laying the full depth for the tallest fall height across a whole area is “very expensive”, so the thickness should follow each piece of equipment, and even turning a play structure can change the thicknesses needed.
That is why a good quote zones the depth. A shallow layer goes under the springers and a deeper one under the climbing frame, each tied to its certificate.
How it works
- 01Send a plan and photosThe site, the surface and the date it must reopen.
- 02We check the groundLevels and where the water drains.
- 03Written quoteBuilt around your reopening date.
How far around the equipment must the surface go?
At least 1.5 metres beyond the equipment edge for falls of 0.6 to 1.5 metres, and more for taller equipment. One installer’s published table, following BS EN 1176, adds two thirds of the fall height plus 0.5 metres once the fall height passes 1.5 metres, and works swing areas out from the chain length. Northumberland County Council’s guidance treats 1.5 metres as a starting point that grows with equipment height, not a fixed figure.
Area is the other half of the price, so measure the impact zone before you compare quotes.
Can a surface be tested on site?
Yes. BS EN 1177’s second method is an on-site drop test, which shows how a surface is performing when it is laid or years later. RoSPA suggests pouring a 500 mm square sample on site for testing by a reputable test house, and offers on-site testing itself. For ongoing checks, see playground inspection.
What should the quote show?
Enough for you to check it against the equipment. Ask for:
- The free height of fall of each piece of equipment.
- The critical fall height certified for the product and thickness quoted, with the certificate.
- The thickness in each zone, and the area of each zone.
- The base build-up, including the stone depth.
- The edge detail; RoSPA notes wetpour does not permanently stick to kerbs, so ask how the edge is keyed in.
- The guarantee; RoSPA suggests expecting at least five years for wetpour.
Is BS EN 1177 a legal requirement?
No, but it is the benchmark. RoSPA describes the BS EN 1176 standards as not mandatory but good practice, and inspectors and insurers work to them. Keep the certificate with your play area records.
Which surface should we choose?
Choose the surface for use and look first, then set the depth by fall height. Our guide to wet pour vs rubber mulch compares the three main options on price, look and upkeep.
FAQs
Does every piece of play equipment need safety surfacing?
Not below 600 mm of possible fall, according to RoSPA, though some cushioning is still advised.
Can we use grass under a 2 metre climbing frame?
Not on RoSPA’s reading of BS EN 1176-1, which accepts grass up to 1.5 metres only.
Why do two quotes give different wetpour depths for the same frame?
Different systems test differently. Compare the certified critical fall height, not the millimetres.
Does damaged wetpour still meet its fall height?
Not reliably where it has cracked, lifted or worn thin. Have it checked and patched; see playground surface repair.
Do you supply the test certificate?
Yes, the certificate for the product and thickness laid comes with the job.
For funding, planning and surface comparisons, see the full list of guides.
Sources
- BSI, BS EN 1177:2018 Impact attenuating playground surfacing: methods of test, published 31 Jan 2019
- RoSPA Play Safety, Play area surfacing, updated Mar 2026
- RoSPA Play Safety, Wet pour surfacing, updated Mar 2026
- RoSPA Play Safety, Grass as a play area surface, updated Mar 2026
- Northumberland County Council, G05 Play equipment guidance, Sept 2014
- RTC Safety Surfaces, Wet pour critical fall height depth and area, undated
- Redlynch Leisure, Wet pour rubber, Sept 2026
- Rubberco, BS EN 1177 compliance checklist, 2026
- GCL Products, WetPour product guide, undated
- Conica, Designing a wet pour playground surface to budget, May 2025
- Soft Surfaces, Wetpour costs, May 2024
- Soft Surfaces, Rubber mulch costs, May 2024
- Abacus, Daily mile track costs, surfaces and installation guide, May 2025
- Wickham Market Parish Council, Play area report, Aug 2022
