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Masonry stair trip hazard using glass - slippery when wet (C) Daniel FriedmanCeramic Tile Walking Surface Hazards

Coefficients of Friction or Slipperiness of Tiled Walking Surfaces

This article describes and includes illustrations of slippery tiled walking surfaces on stairs and walkways.

Page top photo: a combination of glass block, glazed ceramic tile, and concrete on these steps provide a walking surface whose slip and fall hazard is partly a matter of luck: which part of the step will receive the walker's foot?

We discuss COF - coefficient of frictio, SCOF - static coefficient of friction, and DCOF - Dynamic Coefficient of Friction and we cite recommended DCOF for tiled surfaces.

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Tiled Walks & Stairs: Outdoor Slip & Fall Hazard

Collapsing leaking shower pan © D Friedman at InspectApedia.com Various industry, ANSI, ASTM, OSHA, ADA standards recommend a static coefficient of friction (SCOF) of 0.5 or higher (ADA 0.6 or above) and define surfaces with SCOF of 0.4 or lower as "low traction", i.e. "slippery".

But just how slippery is a tiled walking surface? Well, as our friend Mark Cramer says, "... It depends" on both the surface conditions and on how you measure slipperiness.

Photo: this ceramic tile bathroom floor has a low spot that retains puddles of soapy shower watrer and thus adds to the slipperiness of the floor.

COF Coefficient of friction - tests giving a numeric value indicating the amount of friction or slip-resistance between two objects or surfaces

SCOF Static Coefficient of Friction - tests the friction of an object that moves from a standing or still position - its "break-away" point.

DCOF Dynamic Coefficient of Friction - (DCOF) tests the friction of an object that is already in motion - kinetic energy.

Model building codes attempt to address the effects of algae, ice, snow, and water on stairs and walkways.

But because building codes & standards cannot anticipate every possible physical cause of slipperiness on walking surfaces or stairways, codes generally do not attempt to address every possible slippery substance that might be present such as algae, ice, snow, water, even spilled oil or food or wet paint on steps.

Since building codes cannot anticipate every possible slip trip and fall hazard, instead codes and standards typically state something like the text shown below.

1009.5.2 Outdoor conditions. Outdoor stairways and outdoor approaches to stairways shall be designed so that water will not accumulate on walking surfaces.

In other than occupancies in Group R-3, and occupancies in Group U that are accessory to an occupancy in Group R-3, treads, platforms and landings that are part of exterior stairways in climates subject to snow or ice shall be protected to prevent the accumulation of same. - IBC (International Building Code) [43]

or

Slippery conditions on stairways must be corrected. - OSHA standard on temporary workplace stairways [42]

Ceramic tile sloped walkway ourdoors in Two Harbors Minnesota is a slip fall hazard (C) AC InspectApedia.comMost ceramic tile surfaces, unless specifically designed with a rough or anti-slip surface, are quite slippery to start with, and where installed outdoors, in our opinion, are a serious slip and fall hazard that is increased with even the slight moisture deposit of morning dew or fog.

Experts agree that when measuring "slipperiness" or the coefficient of friction (COF), the coefficient of dynamic friction (DCOF) is more relevant than the static coefficient of friction (SCOF) (De march 2019).

More recent developments described by the Tile Council of North America and given below as a PDF, note shortcomings of the classic SCOF, DCOF, and wet DCOF tests, now supplanted by DCOF A Cutest.

Excerpt: When tested using SLS solution as per the procedure in section 9.6.1, tiles with a wet DCOF of less than 0.42 (including by way of example, but not in limitation, polished tiles), shall only be installed when the surface will be kept dry when walked upon and proper safety procedures will be followed when cleaning the tiles.

Because glazed ceramic tile surfaces can be quite slippery even indoors, the tile industry and other experts have studied the coefficients of both static and dynamic friction on ceramic floor tiles.

However for the purpose of comparing the slipperiness of surfaces, experts often study first the static coefficient of friction or SCOF.

Current methods for measuring SCOF for ceramic tile give an SCOF ranging between about 0.60 and 0.85 for dry tile and 0.38 to 0.82 for wet ceramic tile. (De march 2019, BOT method).

The walkway shown here, installed at a home in northern Minnesota, is a particular falling hazard as it is in a climate where snow, ice, frost, and rain are common.

The sharp edge of the paver step insertion at the top of the tile section (these are concrete tiles with a rather smooth finish surface) just adds to the injury risk of a fall.

Above: glazed ceramic tile on this sloped walkway is a fall hazard even if the tile job itself survives the freeze-thaw cycle of northern Minnesota winters.

Just how slippery a tile surface will be depends on a combination of quite a few factors that include not just the static coefficient of friction (SCOF) of the tiled surface and include

Research on the DCOF, SCOF & COF of ceramic tile


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