Situation-Specific Floor Slip Resistance Testing Standards

In the USA, pedestrian slip resistance standards for flooring have traditionally been pass-fail. For instance, a coefficient of friction (COF) of 0.60 might be considered “safe” but 0.59 was “not safe.” This applied to any situation provided the floor was level.

Recently the American National Standards Institute (ANSI) has published some standards that are a bit more detailed. Depending on the value of the dynamic coefficient of friction there is a “lower probability of slipping” potential, an “increased probability …” and a “higher probability.” For the “increased probability” regime, action is recommended, depending on the tile or other flooring’s intended use, to reduce risk.

Under either of these systems there’s no consideration of what the use of the floor is. For example, a 30th floor office building elevator lobby would have the same slip resistance safety standard as a swimming pool deck. An indoor shopping mall in sunny Las Vegas could have the same safety standard as an outdoor walkway in rainy New Orleans. This could put too much restriction on flooring choice in one situation, and/or an insufficient safety standard for another.

Australia and New Zealand, which are decades ahead of the United States in the serious study of slip and fall accident prevention, has established some slip testing standards based on the situation and based partly on some earlier standards established in Germany. As racing fans in Britain say, one should choose “the right horse for the course.” The Australia/New Zealand standards were established in 1999 (Standards Australia HB 197–1999 and ASNZS 4586:1999) and slightly expanded in 2013.

The standards are based on wet slip resistance testing using the pendulum tester, which yields a Pendulum Test Value, PTV. The testing can use either a hard rubber slider or a soft rubber slider (or both). Hard rubber simulates the bottoms of dress shoes, while soft rubber is more representative of bare feet or athletic shoes. The detailed properties of the rubbers are specified by the standard. (There is no correlation between Pendulum Test Values and other tribometer readings, or in general between other tribometer types; therefore the pendulum test must be used to implement these floor slip test standards.)

High PTV corresponds to high wet slip resistance, or a very low contribution of the floor surface to the risk of slipping when wet. Table 1 below shows suggested minimum wet PTV’s for various situations. These can be helpful to building owners who want to prevent slipping injuries and the human and financial costs they incur. “Accessible” in the table refers to areas intended to be accessible to the disabled.

Floor Slip Resistance Testing Standard

Table 1. Slip resistance test value suggestions for various situations

Table 1 shows that six “dry in use” of the 23 categories have no requirement for wet slip resistance. However, these areas should be kept free of grease, dust, tracked-in water, and spills. Generally, at least 10–15 feet of absorbent matting is needed to dry shoe bottoms before reaching the hard floor when it’s wet outside. Ropes along the edges of the mat can keep people from straying off the mat before their soles are dry. A dry mop, washed first to remove any oil, is needed to take up water dripping from raincoats. Umbrella bags on a stand at the entrance can help control drips.

The highest slip resistance in Table 1 is specified for outdoor ramps, and for swimming pool ramps and stairs that lead into the water.

Safety Direct America conducts pendulum testing both in the laboratory and in the field. We also offer the Sustainable Slip Resistance test that is specified by McDonalds Restaurants for assessing how well wet floor slip resistance will hold up after heavy wear from foot traffic.

To follow the 2012 International Building Code, ceramic tiles that are used indoors under wet conditions should also conform to ANSI Standard A137.1 wet dynamic coefficient of friction requirements. Testing uses the BOT-3000E digital tribometer. This instrument, lower in speed than the pendulum, is generally not considered suitable for testing outdoor flooring.

By using appropriate floor slip resistance testing methods and standards, building owners, managers, designers and architects can make intelligent choices in selecting flooring appropriate for each use in order to help minimize risk of slip and fall accidents.

Wet static coefficient of friction testing (SCOF) as described by the misleading ASTM C1028, is no longer considered a valid or reliable slip test method and it was officially withdrawn by ASTM in 2014. Americans caring for buildings and floors must now catch up with the slip resistance standards that have been in use for years in other countries (such as the pendulum test standards) and the new American dynamic COF tests like ANSI B101.3 and ANSI A137.1 in order to help end the epidemic of slip and fall injuries and lawsuits here in the USA. The tools are in place — all that remains is to use them.

Variables that Affect Slip Resistance of Polished Concrete

At the 6th Annual International Concrete Polishing & Staining Conference in Atlanta in September 2013, a panel discussion was organized and chaired by Ken Fisher of Nu-Safe. On the panel were the manufacturer of the BOT-3000E tribometer (floor slip resistance test meter); an Orlando attorney for large international property owners; and slip and fall prevention engineer Dr. George Sotter of Safety Direct America.

Dr. Sotter summarized some of the variables affecting slip resistance of polished concrete. When it’s clean and dry, he said, it’s normally not slippery.  When wet, it might be.

Topical sealers can be a problem. Sotter said, “Think about how an ice rink is made. A liquid, water, is spread on a surface, then solidified into ice. When water is put on top of the ice, that’s a very slippery situation. A topical sealer is also a liquid that solidifies, and with water or other liquid on top it can be treacherous.” Penetrating sealers can be OK if applied properly — the surface roughness is maintained. This means carefully removing the sealer from the surface before it dries. Coatings/sealers with aggregates (such as SolidStepCote from Safety Direct America) can also provide good slip resistance.

Micro-roughness of the surface can be important and is easily measured, but is not a fool-proof indicator of wet slip resistance; a friction test (or coefficient of friction test) is still needed. Too-rough textures may be harder to clean. Concrete finishes that are honed with a finer grit provide lower wet slip resistance, but safe surfaces can be obtained with a surface roughness fine enough not to detract from the appearance. Color pigments don’t necessarily affect wet slip resistance.

Autoscrubbers (scrubbing machines that use vacuum to pick up the dirty water) are usually best for cleaning — a mop is suitable only for smooth floors without greasy/oily deposits. (A very soft autoscrubber brush, like a carpet brush, cleans effectively with minimal effect on slip resistance. Pads — even nonabrasive ones — tend to pick up dirt and may scar the surface.) A monthly high-pressure cleaning can be helpful. Sweeping may spread contaminants and be ineffective on rougher floors. For applications such as shopping malls, cleaning should be done nightly, but in some other circumstances a weekly cleaning is sufficient.

Even a few layers of floor polish can significantly reduce the wet slip resistance.

The most important step in creating a polished concrete floor that’s slip-resistant is to test from the start of the polishing process. The test must include sealer and polish if they are to be used. Better to find out on the first 10 square feet that there’s a potential problem rather than after the whole job is done! Continue testing as the polishing process proceeds; variable slip resistance is considered a hazard. Since concrete batches can vary, the polishing is an in-situ process, and humans are involved, variation can easily happen.

Safety Direct America (SDA) can help by conducting slip resistance tests on-site. The best wet tests for indoor surfaces use the BOT-3000E digital tribometer, which is also available for purchase (at discounted prices) from Safety Direct America. For a level indoor floor, a dynamic coefficient of friction of 0.43 or higher using the ANSI B101.3 test procedure is a reliable indicator. Values as low as 0.30 may be acceptable with periodic monitoring, but consider traction-enhancing products and practices depending on use of the area. Ramps may require increased roughness. Static friction tests are not reliable indicators of safety and can be very deceptive. For outdoor surfaces, where pedestrians may sometimes run (especially when it starts to rain), the pendulum test is preferred because its slider (test foot) moves at higher speed than the slider of the BOT-3000E.

A BOT-3000E slip test described in ANSI A137.1 is by reference part of the 2012 International Building Code, applying to ceramic tile. This test, championed by the ceramic tile industry, often gives a higher DCOF than ANSI B101.3 because less wetting agent is used in the water for the test. However, “Tiles with a wet DCOF of 0.42 are not necessarily suitable for all projects. The specifier shall determine tiles for specific project conditions.” Dry DCOF measurements made using the BOT-3000E may also be of interest. Safety Direct America can help with recommendations of slip resistance for specific situations: food courts, restrooms, sports stadiums, outdoor surfaces, etc.

Wet slip resistance may not be important in areas that can consistently be kept dry. Injury claims might still be filed, and it’s helpful to have dry test results showing that the floor is not a safety problem when clean and dry. However, it’s crucial to remember that surfaces that have excellent dry slip resistance are often very slippery when wet. Dry slip resistance is not an indicator of wet slip resistance.

For external surfaces an 80–100 grit finish with a penetrating sealer should satisfy slip resistance requirements.

Whatever the surface, having documented test results for slip resistance at the end of an installation is very important for the protection of all involved. Regular monitoring is also recommended by American National Standards Institute ANSI B101.3. Quarterly monitoring by a third party is popular because it roughly ties in with the turnover rate of floor maintenance personnel and/or contracts in many buildings. However, semi-annual or even annual monitoring is better than no monitoring at all. Monitoring reports can be highly cost-effective — they have been shown many times to be very discouraging to plaintiff attorneys.

Safety Direct America can provide initial floor slip resistance testing, monitoring and test reports, signed and sealed by a registered Professional Engineer. Contact George Sotter, P.E. of SDA at 800-988-6721 for more information on floor slip resistance testing for your property, or for slip tests in our lab for the flooring you plan to use in a new project.

BOT-3000 Data Features Enhance Courtroom Credibility

Periodic testing of your company’s floors’ slip resistance can detect problems so they can be solved before they cause an accident, and can help verify that there are no remaining problems. Routine monitoring slip tests are typically conducted quarterly, semiannually, or annually. However, various unrelated pedestrian factors such as prescription and non-prescription drug use, intoxication, hazardous shoes, irresponsible pedestrian behavior or downright dishonesty can still lead to claims and possibly litigation. This is where some of the unique features of the BOT-3000E digital floor tribometer (slip resistance tester) shine. If the property owner can prove he or she was not negligent, liability for the alleged accident is not his.

The BOT-3000E can conduct important slip resistance test protocols such as ANSI standards A137.1 and B101.3 (both for dynamic friction), and B101.1 (static friction). However, expert witnesses for the other side may present “evidence” that the floor was slippery even though your tests show it was not — and you know it was not. The BOT-3000E’s features can make your data nearly bulletproof.

The BOT’s screen display (see photo, shown on a tile floor) instantly shows the results of the test, and strip charts of the numerical results can be printed immediately. However, the BOT-3000 data port provides further information in pdf format that can be transferred to a PC or Mac computer in seconds using an ordinary USB flash drive.3000E + printout

Data display and instant printout for ANSI A137.1 DCOF test

 The BOT-3000E’s onboard computer is able to store complete data for each slip test run, including forward-facing photographs. (The on-board camera can be turned off if not needed.)

The sample ANSI A137.1 dynamic coefficient of friction (DCOF) report ANSI A137.1 1259 includes the following information in addition to the DCOF of 0.48:

  • Test location number
  • Ambient-light photos of the location of the test by the BOT’s onboard camera
  • Graphs of instantaneous DCOF for each of the four runs in the test protocol
  • Most recent calibration and verification dates of the instrument
  • Ambient temperature and relative humidity
  • Path length of the DCOF measurement
  • Type and manufacturer’s ID of the slider (test foot) used for the test

The BOT uses “smart sliders” that have circuitry in the slider holder that provides the slider material, serial number, and date of manufacture.

All three types of ANSI test reports on the BOT-3000 include the relevant test information. The number of photos varies from one to six, depending on how many path directions are involved in the particular test protocol. The BOT’s screen display prompts the user with the simple steps involved in conducting each slip resistance test.

Regarding the graphs, initial transient values for dynamic friction are not included in the run averages and thus do not affect the result.

Your BOT-3000 slip test data, collected by you or by a third party designated by you such as Safety Direct America, can help prove that you have exercised due diligence, best possible practice, and have done everything reasonable and practicable to prevent slips and falls — in other words, that the alleged slip and/or fall accident was not due to negligence on your part.

Safety Direct America conducts BOT-3000E field and laboratory slip resistance tests using the methods described above and others as well. Lab tests typically cost $230 per sample. Field test charges depend on location. We have tested throughout the USA as well as from Guam to Bermuda and in Canada.

We can also provide you with your own new BOT-3000E slip resistance tester at a $300 discount. Please phone George Sotter at 800-988-6721 for information.

Misleading ASTM C 1028 Friction Test Continues to Wreak Havoc in the USA

Misguided investments of hundreds of millions of dollars in slippery flooring … pain, suffering, and financial losses to accident victims and their families … lawsuits by the thousands … and lack of consumer confidence in ceramic tile and other hard flooring: these are some of the consequences of a poorly-conceived floor “slip-resistance” test — ASTM C 1028, Static Coefficient of Friction, published and sold by the American Society for Testing and Materials. Floor safety experts in most developed countries have considered this test method to be a joke for many years.

Conceived decades ago as a simple way of testing static friction and giving passing grades to many visually attractive but hazardous slippery floors, C 1028 survives despite the availability of far better test methods. No surprise, because lots of people profit from slippery floors: physicians and hospitals, physical therapists, lawyers, and expert witnesses, to name a few. Slip-and-fall accident victims and the disabled are often mystified as to how so many slippery floors (especially wet ones) came to exist and to dramatically change their lives in an instant.

The C 1028 test measures the amount of force needed to overcome friction of a 50-pound stationary object, barely coaxing that object briefly into motion. The problem is, most people aren’t standing still when they slip and fall — they’re moving. This means that what’s relevant is dynamic, not static, friction. Test methods such as ANSI A137.1 (using the BOT-3000E tribometer, and now part of the International Building Code used in most U.S. jurisdictions and a number of other countries), and the pendulum and Tortus instruments endorsed by Ceramic Tile Institute of America (CTIOA), measure dynamic friction and correlate with pedestrian safety. The pendulum is a national standard for pedestrian friction in at least 49 nations and has been endorsed by CTIOA since 2001.

The Access Board of the U.S. Department of Justice issued a document in 1992 that was taken by many as an endorsement of ASTM C 1028. A static coefficient of friction of 0.60 or higher seemed to appear safe for level floors, and 0.80 or higher for pedestrian ramps.

The Access Board long ago denied any support for, or confidence in, static friction. But like a vampire that keeps coming back, C1028 is still used by many architects, designers and building owners as their only criterion to try to prevent them from successfully being sued because of a slippery floor. It doesn’t necessarily work, because all competent U.S. slip-and-fall forensic experts acknowledge that static friction is not adequate to prevent accidents. For more information on ASTM C 1028, please see www.C1028.info.

Safety Direct America conducts laboratory and field tests using ANSI A137.1, two other relevant ANSI tests, the pendulum, and the Tortus. For those who insist on ASTM C 1028 we conduct that test too — but we do not recommend using it as your sole criterion for slip-and-fall safety.

If you want to prevent slips on your property, contact George Sotter at Safety Direct America, 1-800-988-6721, for our recommendations. We’re consultants to two major cruise ship companies as well as property owners, insurance companies, and attorneys. We wrote the book on slip prevention — see STOP Slip and Fall Accidents! at amazon.com. Have a safe day!

Anti-Slip Transparent Coating Lets Hotels Eliminate Tub/Shower Mats

Most hotels and motels with slippery bathtub and shower floors have been using suction cup mats to give bathers safer footing, albeit only on a small part of the slippery surface. These mats need to be laundered daily or they will harbor bacteria, foot fungus and mold. Because of the laundering the mats deteriorate quickly and need costly replacement. Worse, the guest sometimes doesn’t bother to use the mat and is injured in a fall, blaming the owner for the injuries. Even when the mat is in place, vigorous activities in the shower (if you know what we’re saying) can lead to stepping off the mat, leading to a one- or two-person fall. If a glass shower door gets broken, injuries can be life-threatening.

Safety Direct America’s anti-slip coating SolidStepCote 03 is helping major hotel chains to eliminate these problems while increasing safety. The coating covers the entire walking surface of the tub or shower. It can be applied when the room is vacant and is ready for use in less than 24 hours. It is durable and easy to clean. (Abrasives must not be used in cleaning.)

If 20 or more tubs are coated, the material cost is $10 or less per tub. After cleaning and drying the surface, about 10 minutes of labor is required to apply two coatings. The second coating can be applied 30 minutes after the first, but must have longer to dry before being exposed to standing water.

If the coating eventually starts to show signs of wear it can be touched up without removing the unworn portion. If you wish, additional litigation protection can be ensured by having Safety Direct America test representative tubs periodically and submit a written report, signed and sealed by a state-registered Professional Engineer, for your file to document your due diligence.

Applying SolidStepCoat 03 helps hotels and motels reduce operating costs while improving tub/shower safety, appearance, and hygiene and reducing liability exposure. See the photos below, which are from a bathtub/shower anti-slip coating video on the Safety Direct America web site that demonstrates the application process.

Screen shot 2013-05-19 at 5.39.35 PM

Figure 1. Coating, which dries clear, is applied to clean, dry tub

Screen shot 2013-05-19 at 5.16.27 PM

Figure 2. Optional friction testing documents results for hotel’s file

Screen shot 2013-05-19 at 5.14.29 PM

Figure 3. Hotel owner jumps for joy in SSC03 coated tub. (Kids, don’t try this at home.)

BREAKING NEWS: Dynamic Slip Testing Enters International Building Code!

Slip accident prevention in the USA and Canada finally emerged from the Stone Age when dynamic coefficient of friction testing with a specific test method and safety standard became a verified part of the current International Building Code (IBC) in February 2013. The IBC is used in more than a dozen countries, such as the USA, Canada, Saudi Arabia, and Chile. The new dynamic friction test is conducted using the BOT-3000 digital tribometer and is sometimes called the AcuTestSM.

This is the first time any U.S. national building code or regulation has had specific instructions regarding wet or dry slip resistance. In the past, property owners spent many billions on floors that were unsuitable for their intended use because they were slippery when wet (lobbies, commercial kitchens, pool decks, showers, etc). Use of static coefficient of friction often gave misleading results, causing buyers to think that the flooring they were buying was safe when it in fact was very hazardous. Years ago, the Access Board of the U.S. Department of Justice, which administers the Americans with Disabilities Act, denied any support or responsibility for using static friction tests.

The current (2012; the Code is published every three years) IBC states on p. 435, “2103.6 Ceramic Tile. Ceramic tile shall be as defined in, and shall conform to the requirements of, ANSI A137.1.” Up until recently, this meant using static coefficient of friction (SCOF). The minimum SCOF, ANSI said, “shall be as agreed upon by manufacturer and purchaser.” In other words, the flooring retailer wasn’t involved, and a mistake leading to an accident was the customer’s fault. Now that has changed. According to Tile Council of North America, “any party involved in the chain of sales will be responsible for knowing what the [ANSI A137.1 DCOF] requirement is and what it means.”

The new version of ANSI A137.1 (American National Standard Specifications for Ceramic Tile), published in 2012 with the DCOF test method re-verified in February 2013, specifies (Table 6 on p. 10) a minimum DCOF of 0.42 “for level interior spaces expected to be walked upon when wet.” For a ramp an unspecified higher value is required. We believe this should include consideration of the angle of the ramp and whether the pedestrian is controlling a separate load (wheelchair, shopping cart, gurney, heavy suitcase, etc.). See “Safe Friction Values for Inclined Surfaces (Ramps)” farther down in this blog.

The ANSI tile standard correctly points out “the COF of installed tiles can change over time.” This speaks to the value of periodic monitoring of COF so that action can be taken to solve any problems before an injury occurs. This helps establish that the property owner has used due diligence, best possible practice, and has done everything reasonable and practicable to prevent slipping accidents.

The testing procedure is specified by ANSI in Section 9.6 and names the BOT 3000 automatic testing device. The flooring is wetted with water containing a trace of the wetting agent SLS (sodium lauryl sulfate) to reduce surface tension so that the water doesn’t bead up on the surface. The SBR hard rubber test foot is roughly an inch wide, and curved cylindrically so that only a line of the rubber touches the flooring surface.

Though ANSI A137.1 is specific to ceramic tile, it seems likely that the test method will also be applied to other flooring such as marble, granite, terrazzo, vinyl, etc.

For exterior surfaces, where people are more likely to be running (especially if it’s raining!) we recommend a minimum wet Pendulum Test Value of 36 using the test method specified since 2001 by Ceramic Tile Institute of America. The pendulum is a higher-speed device than the BOT-3000. It is a national standard for pedestrian slip resistance in 49 nations, and it’s been in continuous use for floor friction testing since 1971. It is also specified for the Sustainable Slip Resistance test procedure developed by McDonalds Restaurants and adopted by major cruise ship companies and major property owners to ensure that their new floors will have durable wet slip resistance.

The new IBC specification was developed by a committee representing 58 organizations and was spearheaded by Tile Council of North America (TCNA). Ceramic Tile Institute of America and TCNA deserve credit for resolving what was an unfortunate situation in which a bad test method (static friction) caused life-changing accidents, inappropriate flooring investments, and countless lawsuits. It also led to ceramic tile having a reputation, with many people, of being unsafe. (Time will tell whether the new safety criterion of 0.42 is high enough.) In fact the right ceramic tile, produced in a quality-controlled factory and designed to give good, sustainable wet slip resistance, can be the safest and most versatile type of attractive flooring available.

A new model of the BOT-3000, the BOT-3000E, has begun the verification process to be ruled acceptable for ANSI A137.1 testing. Another test method using the BOT-3000, namely ANSI B101.1 (static friction) now appears to be mostly obsolete. The old static friction method ASTM C 1028 is expected to die a natural death when it comes up for periodic renewal by ASTM.

Another dynamic test method using the BOT-3000, ANSI B101.3, has some small but important details that are different from the ANSI A137.1 test method. The B101.3 method usually results in lower DCOF data, yet has the same basic safety criterion: 0.42 for a level floor. This method might be a better choice for property owners looking for safe new flooring, but it’s unlikely to be used by tile vendors because it’s less favorable to products that are marginal in terms of wet slip resistance.

Safety Direct America offers laboratory and field slip resistance testing using the new ANSI A137.1 AcuTestSM method, as well as the other methods mentioned above. A laboratory  AcuTestSM costs only $179.00, and turnaround is normally less than three business days. Field tests are conducted on a time and expenses basis (nationwide, but from a southern California base). We also offer periodic monitoring (e.g. quarterly or annually) for commercial/industrial premises, and slip-fall expert witness service.

Top 5 Ways of Keeping your Slippery Floor Dry

Many of the most attractive floors are smooth and glossy, and over 99 percent of those are slippery when wet although they often have excellent slip resistance when dry. When they’re near an outside door special care is needed to keep them dry to prevent slip accidents. Here’s how.

1.            Have an overhang outside so that shoe bottoms don’t get wet when stepping out of a car in front of the door, or so that they can dry off while walking under cover from the parking structure to the door.

2.            Keep clean mats in place to clean and dry shoe bottoms before they hit your slippery floor. If snow, ice and/or mud are issues, an abrasive mat should be outside to clean these substances off before entering the building. Inside, there need to be at least 12 feet of absorbent matting to dry the shoes. At home, you probably stop to clean off your shoes at the door, but in a commercial building people just walk straight in. If thousands are walking into an office building (for instance) in the morning, you need enough length matting to dry the shoes after lots of water has already been tracked in.

Don’t expect everyone to walk in laser-straight in on your straight and narrow mat. The mat needs to be wide enough for those who veer off in another direction to go to their elevator or other destination inside.

3.            Now that the shoes are dry, there’s still the matter of dripping wet umbrellas. Have an umbrella bag stand with plastic bags in place at the entrance so people can stow their umbrellas while they continue on their way. These stands are available online from many vendors.

4.            After the umbrellas have been stowed, there are the dripping raincoats, hats, briefcases, suitcases, etc. to consider. Have someone with a dry, oil-free dust mop periodically clean up any water that gets past the mats. Most dust mops when they’re new contain oil to help capture the dust! This oil must be laundered off before the dust mop is used on a smooth, glossy floor — a lubricant is not what you want on that floor.

5.            Ensure regular surveillance to clean up promptly any spills. The frequency of inspections depends on what’s in and around the area, e.g. a bar, coffee bar, lemonade urn, food court, etc.

Don’t make the mistake of thinking that because no one slips on your beautiful, expensive flooring when it’s dry, that that means it’s not slippery when wet. The truth is often quite the opposite.

When planning a new building or renovation, specify flooring with a slip resistance test, preferably the Sustainable Slip Resistance test (as defined by McDonalds Restaurants for customer areas in new stores), so you don’t need to worry nearly as much about slips when there’s liquid around. If your existing floor is still too risky after you’ve implemented the five steps above, have Safety Direct America treat it with the Non-Slip 21 process to improve the wet slip resistance.

IMG_1694

Travel and Dining Apps, Web Sites Report on Slippery Floors

Think no one notices that your business has slippery floors? Check out web sites and apps like TripAdvisor and Yelp. Customers are likely to report slippery floors, and this could attract scammers. (Some of the reports may even be posted by scammers in preparation for their next score!) You don’t need that kind of publicity.

A search of TripAdvisor.com for “Slippery floors” recently included reports of a roadhouse in Austin, TX; a harbourside restaurant in East Greenwich, Rhode Island; an Italian restaurant in Turnersville, NJ; a hotel in Louisville, KY; and tourist destinations in Australia, Peru, Greece, Dominican Republic, England, Mexico, Indonesia, and numerous other countries. Actress Eva Longoria’s popularity didn’t prevent her spectacular restaurant Beso in Hollywood from being sued for an alleged slip and fall. The most beautiful floors are often the most slippery when wet from tracked-in rain, raincoat or umbrella drips, or spills.

If you are “under notice” that you have slippery floors, you need to remediate your floors so there are no slips that are caused by your negligence. “Under notice” means that you knew, or should have known, that the floor was slippery when wet or greasy (say near a restaurant kitchen), or under other frequently-occurring conditions. If there have been complaints or known slips, you knew. If your company is a large one, your safety people should reasonably have known even if you didn’t.

Make sure that new flooring is suitable for its intended use before it’s installed with a slip resistance test and that its slip resistance will stand up under wear from heavy foot traffic. If it’s too late for that, there are numerous ways of remediating a slippery floor. You can apply anti-slip tapes or a do-it-yourself transparent anti-slip coating; or have Safety Direct America professionally apply their Non-Slip 21 transparent anti-slip floor treatment. Periodic (quarterly or annual) monitoring of slip resistance by Sotter Engineering Corporation can help establish that you are using due diligence. Phone us at 949-582-0889 to discuss slip resistance testing and possible fixes for your floor.

Safe Friction Values for Inclined Surfaces (Ramps)

The minimum safe coefficient of friction for a ramp, inclined surface, or slope depends on the angle from the horizontal as well as another factor if the pedestrian is controlling a separate load such as a wheelchair, shopping cart, etc: the ratio of the total weight of the load to the weight of the pedestrian.

For simplicity, common floor friction safety standards for ramps are “one size fits all” — they’re based on the assumption that all ramps require the same increased coefficient relative to a level floor, regardless of the angle of the ramp. Thus a three-degree ramp would require the same increase in friction coefficient as a seven-degree ramp, e.g. an increase from 0.60 to 0.80 for static friction or, for dynamic friction, from 0.42 to 0.45. This can place a restriction on small-angle ramps that’s more stringent than necessary.

Standards may also be based on the assumption that the pedestrian is not controlling a separate weight, such as a shopping cart, wheelchair, wheeled suitcase, or gurney. This is of course often a poor assumption. When a separate weight is involved a higher minimum coefficient of friction is required, whether the floor is wet or dry.

The way coefficient of friction is defined (friction force divided by applied force, or weight) means that the more weight that there is on the pedestrian’s shoes, the higher the friction force is. This works fine when a pedestrian is carrying something — for instance, two heavy shopping bags. The pedestrian gets added friction from the added weight on the shoes, which helps maintain safety despite the added weight that’s being controlled.

However, when added weight is not on the pedestrian’s shoes, but instead on a separate or wheeled load, the shoes don’t get the benefit of added traction. This means that the floor’s minimum coefficient of friction (COF) for safety needs to be higher.

How much higher? Well, an analysis published by Sotter, Stone and McCarthy (ISOES Sotter et al) in Proceedings of the International Occupational Ergonomics and Safety Conference indicates  that the increase in the minimum COF is related to the ratio of the weight of the load to the weight of the pedestrian controlling the load. For a 110-pound nurse controlling a 220-pound load of patient + wheelchair, that ratio is 220/110 = 2.0. The paper’s Figure 2 (see below) shows that for a the maximum ADA ramp angle of 7.12 degrees and a weight ratio of 2.0, the safe coefficient of friction is 0.98, which is 0.38 higher than the assumed level-floor minimum safe COF of 0.60. In Fig. 2 the assumption is that the force exerted by the pedestrian is parallel to the ramp — probably a reasonable assumption for a wheelchair or shopping cart.

Screen shot 2013-02-09 at 4.46.47 PM

 

 

 

 

 

 

 

 

 

 

Should the force (push or pull) exerted by the pedestrian be upward at a 45-degree angle — perhaps true in the case of a manual pallet truck — the situation is as shown in Fig. 3 below. The required minimum COF is lower, other things being equal. This is because pulling the load upward exerts a downward force on the pedestrian’s shoes, increasing the friction.

Screen shot 2013-02-09 at 4.47.05 PM

Using a minimum COF that’s based on reasonable physics makes it possible to provide a safe environment for pedestrians while potentially making things easier on the designer, architect and property owner. The choice of flooring materials is much greater when an unreasonably high COF is not required. However, if loads are being controlled, such as in airports, hospitals and supermarkets, a significant increase in required coefficient of friction for the flooring might be needed.

Screen shot 2013-02-10 at 1.48.38 PM

Stop Slips on Cruise Ships

A slip and fall on a cruise ship can not only ruin several peoples’ dream vacation, but also cost a cruise line company major bucks. Two of the world’s largest cruise ship companies are now using Sotter Engineering Corporation for testing and recommendations to prevent future slipping accidents.

Cruise ships are especially vulnerable to slips due to several factors: unfamiliar surroundings; bare feet on wet surfaces (pool decks, showers, water parks); lots of alcohol consumption (why not?); seniors on multiple prescriptions; flu and norovirus; changing angle of the deck while under way; and other risks.

Because flooring can only be changed out in dry dock, it’s crucial to pick the right flooring from the start for retrofits and for new builds. Vendors’ slip resistance data may be old and unreliable, and unfortunately seldom tell the full story. Testing should include the McDonalds Restaurants Sustainable Slip Resistance test and the new BOT-3000 digital tribometer AcuTest that is soon to become part of ANSI Standard A137.1.

The Pendulum Test Value (PTV) measured in the McDonalds test can be used to determine what areas a given flooring is suitable for. For instance, a wet PTV of 25 or less can be OK for areas that are dry in use. For external stair nosings, pool decks and communal showers, at least 40 (using a soft rubber pendulum slider) is advisable. For brows (gangways) a PTV of 44 or higher may be needed. In all cases where indoor floors get wet it’s best that whenever possible, wet dynamic coefficient of friction by the Acutest exceed 0.42.

A cruise ship’s situation is different from McDonalds’, and the real-world situation on a ship is different from that in laboratory testing. These tests are intended to help cruise ship companies without precluding the use of certain flooring where judgment indicates it should be permissible. In areas where spills may happen, diligence in quickly cleaning them up and drying the floor can play a role in flooring selection. Low-traffic areas are another situation where qualitative judgment may play a role.