ASTM D2047 and the Limits of Static Slip Testing

ASTM D2047 is one of the oldest slip tests still on the books. It was first published in 1953 and uses the James Machine to measure the static coefficient of friction (SCOF) of a clean, dry floor coated with wax or polish. It answers one narrow question: how much grip there is before a shoe starts to move. That was useful in the 1950s for comparing floor finishes. It tells you very little about why people actually fall today.

Here is the problem. People do not slip while standing still on a dry floor. They slip when they are walking, turning, or stepping from a dry surface onto a wet or greasy one. That is dynamic movement, and it is almost always wet. A static, dry test cannot see any of that, which is the whole reason falls happen in the first place.

Where the “0.50” number came from

You have probably heard that a floor is “safe” at a slip resistance of 0.50. That figure traces back to mid-century floor-wax testing on the James Machine, and it was later floated by OSHA as a recommendation. OSHA never adopted it as an enforceable standard, and the old ADA figure of 0.60 was an advisory that was eventually withdrawn. In other words, there is no walkway-safety standard, test method, or peer-reviewed number that makes “0.50 equals safe” hold up under scrutiny. It stuck around mostly because it was easy to pass. Back in the 1950s nearly every floor wax in America cleared 0.50, so manufacturers were happy to cite it.

Most of the static tests have already been retired

Over the years, the standards bodies have withdrawn nearly all of the static (SCOF) methods:

• ASTM C1028 was withdrawn in 2014.
• ASTM F489 was withdrawn in 2005.
• ASTM F1677 and ASTM F1679 were withdrawn in 2006.
• ANSI/NFSI B101.1 was allowed to expire in 2014.

They were pulled or left to lapse for the same reason: measuring grip while a foot is standing still does not predict a slip while a foot is moving. Some of the instruments behind those standards, like the English XL and the Brungraber Mark II, are still used in the field, but the published standards that once governed them are gone.

ASTM D2047 is the last static method still active, and even it is limited to polishes and finishes tested dry in a lab. It was never written to certify that a real, in-service floor is safe to walk on. When a product data sheet leans on a D2047 or C1028 number to call a floor “slip resistant,” it is answering a question nobody was really asking.

How we test instead: the way people actually walk

Since slips happen on the move, we measure friction on the move. Two dynamic methods do that well, and they are the ones we rely on:

• The Pendulum Slip Tester (ASTM E303). It swings a rubber slider across a wetted surface at roughly the speed of a walking heel strike, so it captures how a floor behaves when it is wet, which is the condition most falls happen in. The method is backed by about 50 years of research across dozens of countries, with published interpretation guidance from the UK’s Health and Safety Executive and from Australia and New Zealand. A Pendulum Test Value (PTV) of 36 or higher indicates low slip potential when wet.
• The BOT-3000E (ANSI A326.3). It reports dynamic coefficient of friction (DCOF) and is well suited to verifying a product’s rating and tracking a floor over time.

Both look at the floor in motion, wet, which is where the real risk lives. If you want the longer explanation of why static friction and dynamic friction are not the same thing, we walk through it on our SCOF testing page.

Why this matters for you

If a spec sheet or an opposing expert leans only on a static, dry number, it can label a genuinely slippery floor “safe.” We have measured floors that pass a static test around 0.80 and still read dangerously low when wet, right after real people had fallen on them. A number that does not match what is happening underfoot is not protecting anyone.

Every floor we test gets measured the way it is actually used, and every result goes into a report structured to the ASTM F2048 format so it holds up if it is ever questioned. For more on how the standards fit together, see our standards overview.

Need reliable, real-world slip testing before you install a floor, or after someone has already gone down on one? We are here to help.

Get a free quote or call 1-833-DIAL-WMG to have your floors tested.