Coefficient of friction (COF) is a mathematical term
used to describe the effect of dragging one substance
(shoe sole material) over another (flooring surface).
This coefficient is a measurement of the relative
ability of various surfaces to resist the sliding or
slipping of the selected material.
The slip-resistance of ceramic tile in ordinary
applications is comparable to that of most hard surface
flooring materials and it is significantly better than
some.
Unglazed tiles have a greater slip-resistance than
glazed tiles and are commonly recommended for areas
subjected to high water spillage. irregular or textured
surfaces can be confused for slip-resistant surfaces.
Because a glazed tile is rough or not glossy, doesn't
necessarily mean it is slip-resistant. Even many
irregular or textured unglazed tiles can become slippery
when wet, allowing surface hydroplaning.
Many glazed and unglazed tiles can feature abrasive grit
on their surface, increasing their slip resistance
substantially. These tiles are commonly installed in
public areas with direct access to the outdoors.
Corundum grit surfaces can introduce an element, when
traffic acts upon the surface, which will add to the
floors deterioration and can be too slip-resistant, when
excessive.
Carborundum grit, which appears to be black reflective
speckles into the surface of an unglazed tile, will wear
flat and become ineffective.
Please Note: that any tile or other hard surface
flooring can become slippery when wet or improperly
maintained. Slip resistance varies with the many types
of footwear, soiling, and cleaning regimen.
Polished wet surfaces give false slip-resistance
readings, due to a suction effect developing between the
tile surface and sole materials.
Even under dry conditions the testing of polished
surfaces is questionable.
Avoid trying to raise the COF by using coatings - they
will peel, blister, discolour and mar, creating a
difficult floor surface to maintain...aside from
providing unsatisfactory slip-resistance.
SLIP
RESISTANCE
The anti-slip qualities of the tile alone do not make
walking safe in risky situations.
Many factors are involved, and all should be taken into
consideration at the planning and installation stages:
Configuration of non-traffic and
traffic areas, adjoining floors of different friction
coefficients
Proper fixing
Proper maintenance and cleaning
The United States ANSI method (ASTM C1028) gives,
through the use of a force gauge (horizontal
dynamometer) pull meter method, the static friction
coefficient of the surface.
.
Equal to or greater than
.60 excellent
friction
Equal to or greater than .50
adequate
Equal to or less than .40
caution necessary
The USA Occupational Safety & Health Administration (OSHA)
currently recommends that the static COF be at least 0.5
for all walkway surfaces under both wet and dry
conditions. The Americans Disabilities Act (ADA)
recommends the dry static COF of 0.6 on any flat or
horizontal surfaces both wet and dry, but 0.8 for any
inclined or ramp areas.
COF is defined as the friction force opposing sliding
motion divided by the force normal to the surface.
People walk differently (most people demand a consistent
COF of between 0.25 - 0.3 walking normally) Long fast
strides demand a higher friction. Although slippery
surfaces or steep slopes provide low COF, we often
perceive the potentially dangerous floor, shorten our
stride and walk slowly.
Including the presence of contaminants a 0.4 COF should
be demanded for safety.
Millions of combinations possible: several shoe
materials & design features, floor materials, surface
profiles, degrees of wear and cleanliness, type & amount
of contamination, walk patterns & angle of contact, body
weight, vertical force, rate of weight application,
lighting & surface perception, eyesight, inebriation,
medication, etc.
It’s important to realize that the COF testing is
flawed. The current testing methods, both in the testing
laboratory and in the field, are flawed. In addition,
there are so many other factors and shoe materials used
in real pedestrian traffic conditions that the results
are inconclusive at confirming how a surface or tile
will provide adequate slip-resistance; especially, once
down and subjected to periods of differing wear abrasion
and daily maintenance regimens.
The best solution, the best objective, is to provide a
superior COF and maximize these characteristics for
industrial, commercial, and residential needs.
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