1 SLIP-RESISTANT FLOORING

Tom Murphy, Vice President Marketing General PolymersIndustrial and Marine Coatings Group,

The Sherwin-Williams Company

Abstract: Anti-slip or textured seamless floorsare specified in situations where exposures towater, oils, greases or other process contaminantsare anticipated. This discussion will focus on thevarious types of slip-resistant flooring options andwill briefly address the maintenance of thesefloors.

Introduction

Most people dont think much about floorsurfaces until there is a problem. For instance,personnel safety and potential liability may onlybecome major issues when floors become tooslippery under normal use conditions. Slips andfalls are the second leading cause of work relatedinjuries. In fact, they are one of the highest (30%of all claims) causes of workers compensationthroughout the world. The economic impact toboth individual companies and to the nation isstaggering. Each year, slips and falls account formore than 12 million accidents and over 100,000disabling injuries in the United States alone. Lostproduction, medical expenses, liability premiumsand legal settlements represent a major costassociated with slips and falls. According to theNational Safety Councils 1999 Injury Facts, thelifetime costs associated with slip and fallaccidents exceed $12 billion in the US.

Maintaining floors properly to preventunwanted hazardous slip conditions in kitchens,restrooms, production environments and evenpublic access lobbies depends on the type offlooring system and conditions of use. Typically,textured seamless floors are specified in situationswhere exposure to water, oils, greases or otherprocess contaminants is anticipated. Often, awet environment is only considered wet

because it requires frequent cleanings to maintaina hygienic plant environment. Further, the degreeof texture selected must be matched with theconditions of operation because the textureimpacts the slip resistance and maintenanceprocedures required, including the types ofcleaners used and the techniques for keeping afloor clean and in good order.

Standards and Measurements

The slip-and-fall issue has beenrecognized as a major problem. Thus, a number ofprocedures, policies, recommendations andregulations have been issued to help prevent slip-and-fall accidents. The standard established bythe Occupational Safety and HealthAdministration (OSHA) for determining properslip resistance of floors is a 0.5 static coefficientof friction (SCOF) as measured under drylaboratory conditions. This standard wasoriginally proposed as a non-mandatory appendixitem, and was never adopted. Similarly, theAmericans with Disabilities Act (ADA)recommends the standard be raised to 0.6 SCOFbut that is recommendation, not a statute.

The American Society for Testing andMaterials (ASTM) refers to a testing procedure,which utilizes the James Machine in a drylaboratory condition but cannot be preformed inthe field. This method is not recommended forwet surfaces or for rough or corrugated surfaces.This test method considers flooring materials tobe slip-resistant if the static coefficient offriction is 0.5 or greater. Ironically, floors whichhave a high SCOF (0.8-1.0) can actually causemore problems as trip hazards.

Copyright 2003 by SSPC: The Society for Protective Coatings

2One of the most frequently sited standardsin the industry is attributed to UnderwritersLaboratories (UL). Here again the benchmark is0.5 SCOF. UL does not, however, certifyproducts for slip resistance.

Of all of the standards available the NavyMIL-D-3134J Specification for Deck CoveringMaterials (1988) comes closest to outlining thetest procedures and detailing the slip resistantproperties for flooring materials. Aimed atreducing accidents on shipboard interior decks,MIL-D-3134J outlines the procedure for testingsurfaces with dry, wet (with 4 percent salt), andoily (SAE 10W) conditions This procedure alsooutlines the standards for non-static coefficient offriction (NSCOF). Table 1 lists the friction factorsfor each condition.

SCOF NSCOFContactingSurface

Dry Wet Oily Dry Wet Oily

Leather0.6 0.5 -- 0.3 0.4 --

Rubber 0.6 0.7 0.3 0.4 0.7 0.1Table 1. Friction Factors

Factors Affecting The Real Life Slipperiness

The Navy standard begins to address someof the issues that affect the slipperiness of asurface. A surface may not be slippery to oneperson; yet the next person can fall on the samefloor in the same conditions. Why? Threefactorsthe surface, the individual and theenvironment -- contribute to this equation.

The Surface: Flooring material (surface resilience & porosity)

Texture or topographyCleaning and contaminationWear

The Individual: FootwearContact AreaWeightVelocity

The Environment: TemperatureHumidity

The Surface

As one would expect, the flooring materialitself significantly influences the degree of slipresistance. Materials that are soft, such as rubberor urethane, are less slippery than hard surfaces,such as ceramic or metal. Unfortunately, some ofthe softer materials are not viable for industrialapplications. These surfaces general require anabrasion-resistant surface that can withstandheavy impact and traffic conditions. Toaccommodate these conditions most slip-resistantindustrial floors are composed of a polymericmaterial (Shore D >50) usually incorporatingsome degree of aggregate.

The porosity of the floors will affect theslip resistance under wet conditions. Forexample, concrete absorbs water, while waterstays on the surface if coated with epoxy. Toaddress this issue, polymeric floors are installedwith various textures. His allows the water (orother contaminants) to move out of the way of thecontacting surfaces. The texture or topographycan be varied by applying a stipple finish polymerto an aggressive texture using bonded aggregate.Aircraft carriers illustrate the extreme non-slipsurface with a high peak-to-trough variation in theprofile. Most industrial environments requireonly a slight non-skid texture to avoid slips andfalls. This can be accomplished using a fineaggregate incorporated into the topcoat surface ofthe floor.

The degree to texture has a directcorrelation to the ease of cleaning. A high profilefloor finish will be hard to clean and eventuallyloses its texture due to the inability to remove thedirt. Some cleaning materials will also leaveresiduals that can contribute to the slipperiness ofthe floor. It is best to match the cleaner to thecontaminant followed by effective removal of thedetergent and contaminants.

All flooring materials wear with use. Thephysical erosion of the floor will polish thesurface increasing the risk of slipperiness.Depending upon the materials used in the floor,this process can be extended greatly. Some slipresistant additives are composed of plastic beads

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3which cannot withstand heavy traffic for morethan about year. Silica sand used as a non-skidadditive will have much better wear propertieswhile aluminum oxide performs the longest. Theability of the binder resin to hold the aggregatewill also impact the longevity of the slip resistantsurface. Polyurethane elastomers, typically usedin parking decks, have poor adhesion propertiesand will eventually lose the surface aggregate.Epoxies, on the other hand, have excellentadhesive strength and will hold the aggregatebetter.

The Individual

Individuals working within industrialenvironments come in all shapes and sizes. Thiswill affect their traction. Surface slipperiness notonly depends upon the type of shoe (e. g., materialand texture of the sole), but will also depend uponhow much surface area is in contact with thefloor, and the force of contact between the twosurfaces. Although the old saying goes, thebigger they are, the harder they fall, in reality,the bigger they are, the less likely they are tofall.

The physics or motion describes thevariables associated with slip and fall conditions.The velocity, mass, friction, inertia, accelerationand force all play a role in slipperiness. The fasteran individual is moving, the less force is directeddownward to the contact surface and the less timethe two surfaces have to adhere. If thismovement is at an angle, such as when someonewould be turning a corner, the more force isdirected away from the contact. Just as in parkingdecks where exit spirals require more aggressiveprofiles, so it is in industrial applications whereindividuals (or wheeled traffic) have a tendency torapidly change directions. Objects will continueto move in the same direction at the same speedunless acted upon by another force.

The Environment

It is obvious to us all that wet is moreslippery than dry and that ice is slicker than

water. It should be no surprise that temperaturecan affect the degree on slip resistance on asurface. Most materials become harder as thetemperature drops. Compound this with the affectof moisture on the surface - either from theindustrial process, humidity or dew point - and itis easy to understand that the surface will be moreslippery in colder environments.

Weighing the Conditions

The four different environments describedbelow represent various seamless flooringapplications that illustrate the spectrum ofconditions to which floors are subjected.

Food processing represents the mostaggressive flooring environment. Food andbeverage production facilities must maintain aclean environment to protect the safety ofemployees and the condition of goods beingproduced. Processing and packaging areas aretypically wet, often requiring steam cleaning.Foodstuff contaminants are frequently acidic.Flooring systems for these environments mustwithstand inherent chemical and abrasionconditions, as well as provide a safe, slip resistantsurface for production personnel. Consequently,textured flooring systems are commonly used inthese areas. Concrete alone will not handle anacidic environment and will become slippery withaccumulation of fats, oils and water.

Urethane mortar surfacing systems areuseful in these applications to withstand combineddeleterious effects of thermal shock from steamcleaning and mechanical and chemical attack. Inareas were thermal shock is not a concern slipresistant coatings can be installed. Slip-resistantfinishes provide safe walking surfaces under wet,dry and contaminated conditions.

Heavy manufacturing conditions varybased upon the production or assemblyenvironments. Heavy manufacturing andassembly plants must address the issue of slipresistance due to the exposure to oils andparticulate matter. A flooring system in this

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4environment also must withstand anticipatedeffects of heavy traffic and mechanical abrasion.Slip hazards in these facilities can be minimizedby combining appropriate degree of texture withproper and timely maintenance procedures.

Commercial kitchens, cafeterias andrestaurants typically represent wet and soiledconditions with low foot traffic. Most commercialkitchens and cafeterias do not undergo the samedegree of physical abuse and steam cleaning asfood processing facilities, but slip resistance andmaintenance of a clean environment are equallyimportant. In these situations, a more decorativeseamless floor such as a quartz broadcast ordecorative troweled system often selected. Thesesystems typically receive a textured finish, aswell, to insure safety.

Lobbies and restrooms are mostly dry withlight traffic, but wet conditions may occuroccasionally. Flooring systems for lobbies andrestrooms are generally selected based uponaesthetics. Light foot traffic and routine cleaningtypical of these areas may not dictate the need fora textured floor system. Terrazzo, marble and tileusing an ADA (Americans with Disabilities Act)

compliant sealer are often installed to maintain thedesired slip-resistant surface in these areas. Onramps and risers these smooth finish floorsrequire the installation of non-slip strips, usingepoxy and alundum or other fine aggregate.

Figure 1. Slip resistant Strips in Terrazzo

Table 2. Representative Conditions Requiring Slip Resistant Flooring

Food Processing HeavyManufacturing

Kitchens Lobbies/Restrooms

Highest Selection Priority Performance Driven Performance Driven Aesthetic &Safety

Highly Decorative

Exposures Thermal ShockAcid ExposureWet ConditionsProtein Soils

Impact ConditionsHigh WearOils, GreaseDust, ParticulatesCrude Soils

ConsiderationsWet ConditionsGrease, OilsFoot TrafficProtein Soils

Weather RelatedExposurePotential WetConditions

Cleaning Requirements Extremely ImportantRequired byRegulations

Safety Driven Safety andHygieneDictated

Aesthetics &Hygiene

Texture High-Medium Medium Medium-Low Low to None

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5Marrying Texture with Safety

Texture on a seamless floor can beachieved in several ways. The final topcoatapplied to a flooring system may contribute to itsslip resistance. Coatings with a stipple finish andsatin finish will create surface irregularities thatmay help control slip resistance. Smooth flooringfinishes, especially epoxy coatings, tend to abradeand increase in slip resistance characteristics overtime.

In more aggressive environments, texturemay be built into the floor using variousaggregates. Light service areas can utilizepolypropylene beads to yield a slight texture.Kitchens and shower rooms frequently utilizecolored quartz broadcast floors, which maycontain a homogeneous texture based upon theinstallation procedure. Application of grout coatsand topcoats of clear epoxy or urethane actuallyreduce the finished floor texture.

An aggressive quartz broadcast floortexture may use a single coat of polyurethane thatfollows the profile and is applied at lowmillage. A 100% solid, zero volatile organiccontent (VOC) epoxy topcoat, on the otherhand, will fill the profile and can be appliedthicker reducing the overall texture.

Heavy manufacturing conditions require amore durable texture that will not be crushed byforklifts and other heavy vehicles. Silica sand orother harder aggregates, such as aluminum oxide,garnet or granite, is incorporated into the finishsurface of slurry/broadcast floors and _ trowelapplied resurfacing systems to achieve slipresistance. Varying the size of the aggregate alsoimpacts the degree of slip resistance. Largeraggregates, such as a 30 mesh silica sand; providegreater degree of slip resistance on a surface thanthe smaller size 40-60 mesh silica.

Figure 2. High Viscosity Coating

There are a number of high viscositycoating products available which take advantageof both the unique profile surface texture of theresin in addition to the incorporation of non-reactive aggregates or grit, such as Kevlar,which contribute to the slip resistance of thesurface. Liquids and other contaminants flow intothe valleys leaving the high-traction peaksexposed. If the peaks ever begin to wear away,they expose fresh grit, providing excellent slip-resistance for years.

Figure 3. High viscosity coating with fine grit

Wen-Ruey Chang and Associates at theLiberty Mutual Research Center for Safety andHealth has studied the role of surface roughnessfor both floor surfaces and footwear. Thisgroups studies concluded that the Coefficient ofFriction (COF), a measure of the inverserelationship between friction and slipperiness, issignificantly impacted by the microscopicroughness of the combination of the sole and thefloor surfaces. This principle helps to explainextreme variances obtained when various waxesand sealers are used on textured floors. It isimportant to insure that ADA (American withDisabilities Act) compliant sealers and

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6maintenance materials are used in lobbies andrestrooms where physically noticeable ormacroscopic surface texture is not incorporated.

Figure 4. ASM 725 Slip Meter Illustration

In independent studies the ASM 725 SlipMeter (American Slip Meter, Inc.) was used tomeasure the static COF of various dry industrialflooring systems with smooth and texturedsurfaces. Two different grades of aggregate wereused, a 40/60 mesh silica sand and a moreaggressive 30 mesh silica sand. Results indicatedthat a smooth surface complies with ADA 0.5COF recommendations in dry conditions, but theaddition of texture to the flooring systemdramatically increased the COF for both leatherand neolite (rubber) soles. The 30 meshaggregate improved slip resistance as representedby an increased COF.

Effect of Texture and Footwear on COF in Dry Conditions

0.00

0.20

0.40

0.60

0.80

1.00

1.20

Smooth 40/60 MeshBroadcast

30 MeshBroadcast

Flooring System

CO

F Leather dry

Neolite dry

Figure 5.

These tests were duplicated with oilyconditions. The smooth surface was below saferecommendations and both textured surfacesimproved the COF. It must be noted that althoughthese tests provide relative performance and validcomparison, the static measurement of slipresistance may not fully reflect the degree ofslipperiness of the dynamic interaction of anindividual walking. By definition, the static meterdetermines the amount of force necessary to

initiate movement of a weight. Water and oil willexhibit a cohesive force with stationary objects.The amount of force required to maintainmovement on these surfaces is significantly less.

Effect of Texture and Footwear on COF in Oily Conditions

0.00

0.20

0.40

0.60

0.80

1.00

1.20

Smooth 40/60 MeshBroadcast

30 MeshBroadcast

Flooring System

CO

F Leather oil

Neolite oil

Figure 6.

While in most food processing areas a wetenvironment exists, conditions can range fromextremely wet in processing rooms to mostly dryin packaging areas. Aluminum oxide is used toprovide a slip resistant surface in areas subject tothe most extreme conditions. The angular natureof this aggregate yields a high coefficient offriction. Figure 7 illustrates that footwearcomposed of neolite (rubber) tends to providesafer COF than leather.

COF in Wet Conditions

0

0.2

0.4

0.6

0.8

1

1.2

Broadcast w/AlOx Broadcastw/topcoat

Broadcast W/30mesh

Flooring System

CO

F Leather

Neolite

Figure 7.

Figure 8 shows, in dry, wet and oilyconditions, the mortar system with broadcastaggregate maintains a high level of slip resistance.When an epoxy topcoat is applied over thealuminum oxide aggregate the COF decreases.

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7COF with Varying Surface Texture

0

0.2

0.4

0.6

0.8

1

1.2

Broadcast w/AlOx Broadcastw/topcoat

Broadcast W/30mesh

Flooring System

CO

F

Dry

Wet

Oil

Figure 8.

Cleaning a Textured Surface

Without an effective cleaning procedure, atextured floors coefficient of friction may bequickly lost. The first and perhaps most complexstep in cleaning a textured floor is choosing thecorrect cleaning chemical for the specificapplication, based on amount and types of foreignmatter, type of flooring surface and the particularcleaning process. Following the floormanufacturers cleaning and maintenancerecommendations is a responsible way to decideupon the type of cleaning chemical to use. If norecommendations are given, then it is necessary tomake a determination based on a number offactors, including the type and amount of dirt andthe chemical resistance limitations of theenvironment, especially the floor. There are twotypes of cleaners that work especially well: theseare a fortified alkaline cleaner for light tomoderate soils and the high alkaline cleaner formoderate to heavy soils. Textured floors willgenerally require the use of squeegees, steam orwater spray or floor cleaning machines. Mopsand sponges will not work. Follow themanufacturers recommendations for use whencleaning with automated scrubbers or hard rubbersqueegee. Most cleaning procedures require

agitation, dwell time to effectively solubilize thecontaminants prior to removal.

Recoating

Sometimes, floor maintenance involvesmore than cleaning. Maintaining a slip resistantsurface may mean providing additional friction.With friction comes wear. All surfaces exposedto constant use will show erosion. Maintaining atextured floor requires periodic recoating andrenewed texture application. In low foot trafficconditions and light cleaning programs, thisrestoration will be required rarely. Extremeconditions will require more frequentmaintenance at regular intervals.

To assure proper maintenance of anyfloor, textured or smooth, standard maintenanceprocedures for each environment should delineatethe frequency of cleaning needed, the correctcleaning agents and the appropriate tools.Thorough cleaning and maintaining a texturedfloor presents a challenge to the maintenancestaff. Safety of personnel is of primaryimportance, and the energy and cost associatedwith maintaining a safe environment isinconsequential compared with the cost of lowmorale and potential medical liability.

Conclusion

The environment of use will dictate thedegree of slip resistance required. Wet and oilyconditions, especially with heavy soil, will requirehigher degrees of texture and more aggressivecleaning procedures. Maintaining the floor withproper cleaning procedures and recoating arenecessary to effectively provide a safe slipresistant floor.

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