Slip resistance in wet barefoot areas is one of the most specified and least consistently tested properties in water park and aquatic centre design. Two projects can both claim to meet "anti-slip" requirements and still deliver surfacing that behaves very differently underfoot.

Why the test method matters more than the label

Slip resistance is not a single property. It depends on the surface texture, the contaminant, the footwear or lack of it, the gait of the person walking, and the slope of the surface. Different test methods capture different combinations of these variables, and a product can score well on one while performing poorly on another.

Ramp tests

DIN 51130 measures the angle at which a person wearing standardised safety footwear begins to slip on an inclined surface covered with oil. Results are grouped into classes R9 to R13. Despite its wide use, the standard is often misapplied in leisure facilities: it specifies oil as the contaminant and safety shoes as the footwear, which does not describe a barefoot guest on a chlorinated wet pool deck.

DIN 51097 addresses that gap directly. It uses bare feet and water as the contaminant, on an inclined surface, and groups results into classes A, B and C. For pool surrounds, shower areas, changing rooms and water park decks, this is the relevant test rather than DIN 51130.

Pendulum tests

EN 16165, which superseded the earlier EN 13036 series, uses a pendulum test to derive a Pendulum Test Value. The method is widely used in the United Kingdom and appears in the Health and Safety Executive's guidance on slip risks. Certification typically reports both a wet and a dry PTV.

ASTM E303 applies the same pendulum principle in the United States, reporting a British Pendulum Number.

Barefoot assessment

Some specifications now require a test that explicitly models the barefoot walker and reports a slip risk classification alongside the angle. This is the closest available approximation to what a guest actually experiences stepping out of a pool.

The problem with a single number

A common specification failure is to write "slip resistance R11" or "PTV 36 minimum" without stating which test produces that number and under which conditions. R11 from DIN 51130 and 36 from a pendulum test are not comparable figures, and a contractor can meet the letter of the specification while delivering a surface that is not safe in the intended use.

A specification that actually controls the outcome names:

  • The test standard and the class or value required
  • The surface condition being assessed — wet, dry, or contaminated with the substance present in service
  • Whether the assessment is barefoot or shod
  • The location on site where the tested surface will be installed, since a slope of one degree and a slope of five degrees produce different slip risks from identical material

Texture, drainage and geometry

Slip resistance is not only a material property. Three design factors change the effective performance of any surface.

Drainage. Standing water is the primary cause of slip incidents. A textured surface that holds water in shallow pools behaves worse than a smoother surface that drains. Falls, cross-falls and drain spacing matter as much as the material.

Texture profile. Deep, coarse texture improves wet grip but creates cleaning difficulty and, in barefoot areas, discomfort. The balance is different for a pool deck, a splash zone and a changing room floor.

Transitions. Most slip incidents occur at transitions — the pool edge, the top and bottom of steps, the change from wet deck to dry walkway. These are where the surface changes and where attention drops.

What good practice looks like

Projects that perform well over time tend to share four characteristics:

  • Barefoot-relevant test methods specified for barefoot areas, with DIN 51097 or a barefoot PTV assessment cited explicitly
  • Slip testing performed on the installed surface, not only on a manufacturer's sample
  • Re-testing after the first full operating season, because texture wears and contamination accumulates
  • Documented cleaning regimes, since surfactant residue from cleaning products can reduce slip resistance significantly

The standards are tightening

Several jurisdictions have moved in recent years from voluntary guidance to mandatory performance requirements for public aquatic facilities, and insurers increasingly ask for documented slip test results as a condition of cover. For operators planning a renovation, this means the replacement surfacing may need to meet a standard that did not exist when the facility was built.

Specifying to the correct method at design stage is considerably cheaper than re-surfacing after an incident.