Slip Resistance and Auto Scrubbing: Why Floors Get Slippery and How to Fix It
How auto scrubbing raises or lowers slip risk: what ANSI A326.3 DCOF testing measures, OSHA 1910.22 duties, residue from overdosing, and a diagnostic.
Key takeaways
- A floor that gets more slippery after it is cleaned usually has a residue problem from overdosed chemical or poor rinsing, not a flooring problem.
- ANSI A326.3 wet DCOF testing is a product-specification method, and the commonly cited 0.42 value is a guideline for selecting flooring, not a guarantee that a floor is safe.
- OSHA 29 CFR 1910.22 requires walking-working surfaces to be kept clean, orderly and, so far as practicable, dry.
- Auto scrubbers reduce slip risk compared with mopping because they recover the water, but only if the squeegee and vacuum are working.
- Use measured dilution, full recovery, and periodic clear-water rinsing to keep traction stable.
Floor scrubbing affects slip resistance in two directions. Done well, it removes grease, soil and polish buildup that reduce traction, and an auto scrubber recovers the water instead of leaving a wet film. Done badly, it leaves surfactant residue from overdosed chemical, water in the machine's path, or polished-smooth floor surfaces, and the floor becomes more slippery than it was before cleaning.
This is general guidance for facility and cleaning teams, not legal advice or a substitute for a professional slip assessment.
What slip resistance means
Slip resistance is the friction available between a shoe and a floor surface. It is usually expressed as a coefficient of friction (COF), a ratio with no units. Higher numbers mean more grip. Dynamic coefficient of friction (DCOF) is the friction measured while one surface is already moving across the other, which is closer to what happens when a heel strikes and starts to slide.
Slip resistance is not fixed: the same tile can be grippy when clean and slick under a film of soapy water or oil, so cleaning practice matters as much as flooring selection.
ANSI A326.3: what it measures and what it does not
ANSI A326.3 is the American National Standard test method for measuring wet DCOF of hard surface flooring materials. In broad terms, it uses a specified tribometer with a standardized rubber slider dragged across a floor wetted with a dilute detergent solution, so results are comparable between products and labs.
The value most people associate with it is 0.42. The standard sets out a classification approach in which hard surface flooring intended for level interior spaces expected to be walked on when wet should generally have a wet DCOF of at least 0.42 when tested by that method. Treat that number carefully:
- It is a product-specification guideline. It helps architects and specifiers choose flooring suited to an intended use.
- It describes a test condition, not your floor. The test uses clean water with a small amount of detergent. Real floors carry grease, soil, polish, dust, and cleaning residue, all of which can change traction substantially.
- It does not cover every use. Ramps, exterior areas, pool decks, commercial kitchens and areas with oil contamination involve different conditions, and the standard itself notes that additional factors and higher slip resistance may be appropriate in such areas.
- It is not a guarantee. The standard is explicit that many factors influence slip risk, including footwear, gait, lighting, contaminants, and maintenance. A floor above 0.42 can still be hazardous.
For an in-service measurement, use a qualified third-party tester rather than the original product data sheet.
OSHA and the general duty to keep floors clean and dry
For workplaces covered by federal OSHA, the walking-working surfaces standard at 29 CFR 1910.22 requires employers to keep places of employment clean, orderly and sanitary, and to keep floors, so far as practicable, in a clean and dry condition. Where wet processes are used, employers should maintain drainage and provide dry standing places, such as mats or platforms, where practicable. Walking-working surfaces must also be kept free of hazards like spills, loose boards and protrusions.
OSHA does not specify a numerical DCOF. The practical expectation is that you clean, you remove water and contaminants promptly, and you control hazards while work is in progress. An auto scrubber is one of the best tools for meeting that expectation because it scrubs and recovers in one pass, rather than leaving a floor wet the way a mop does. See auto scrubber vs mop for the operational comparison and floor scrubber safety for operator procedures.
How scrubbing changes slip risk
Ways scrubbing makes floors safer
- Removes grease and oils that sit on the surface and act as a lubricant.
- Recovers solution and soil instead of spreading them, leaving a damp-dry floor in seconds rather than minutes.
- Cleans the micro-texture of slip-resistant tile before soil fills it.
Ways scrubbing makes floors more slippery
- Overdosed chemical. Surfactants left behind form a thin film. When the next liquid hits the floor, that film turns slick.
- Water left behind. A worn or misaligned squeegee, clogged vacuum hose or full recovery tank leaves trails and puddles. See scrubber not picking up water.
- Wrong chemical for the floor. Some floor finishes and "shine" cleaners leave a polymer film. On a textured tile this fills the profile.
- Over-polishing. Fine pads at high speed can burnish surfaces too smooth.
- Grease moved, not removed. Neutral cleaner at low flow spreads kitchen oil into a wider film.
Diagnostic steps for a floor that has become slippery
Use this as a field procedure. Work through it in order and write down what you find.
- Confirm the pattern. Is the floor slippery everywhere, only in traffic lanes, only near entrances, or only when wet? Lane-only slipperiness points to wear or polishing; whole-floor slipperiness points to residue.
- Check the chemical. Read the label dilution. Measure how the operator actually fills the tank. If there is no measuring cup or dispenser, assume overdosing. Check whether the product is a neutral cleaner, a degreaser, or a cleaner with added "gloss" or "restorer" polymer.
- Do a residue test. Wipe a clean dry area with a damp white cloth, then rub thumb and finger on the cloth. A soapy or slick feel, or a cloth that foams when squeezed, indicates surfactant residue.
- Do a water test. Pour a small cup of clean water on the floor and walk on it in normal work shoes. Compare with a recently rinsed patch. If the rinsed patch is noticeably grippier, residue is the cause.
- Inspect the machine. Check the squeegee blade for nicks and rounded edges, check vacuum hose for clogs, check the recovery tank float and lid gasket. Run a pass and look for trails.
- Check for contaminants. Look for equipment oil, kitchen grease, polish overspray, and standing water at drains and entrances.
- Check the floor surface. Look for worn texture, polished lanes, or coating applied over slip-resistant tile.
- Fix the most likely cause first. For residue: run two or three clear-water rinse passes, then restart with measured dilution. For machine issues: replace the blade or clear the vacuum. For grease: switch to an alkaline degreaser with a grit brush.
- Re-check after a week. Repeat the water and residue tests. If traction has not recovered, involve the flooring supplier or a qualified slip tester.
Practical scrubbing settings for good traction
The table below summarizes choices that keep slip resistance stable. Use the pad selector for floor-specific pad guidance.
| Setting or choice | Goal | Good practice | What to avoid |
|---|---|---|---|
| Chemical dilution | No residue | Measure every fill, or use a dosing system | "A splash extra" per tank |
| Chemical type | Clean, not coat | Neutral cleaner daily; degreaser where grease exists | Cleaner-plus-gloss products on textured tile |
| Rinse | Remove build-up | Clear-water pass weekly, or after every degreaser clean | Never rinsing |
| Pad or brush | Clean texture | Brushes on textured tile; red or blue pad on smooth floors | White pads or burnishing on slip-resistant surfaces |
| Solution flow | Enough to clean, all recoverable | Medium; lower in tight spaces | Flooding beyond what the squeegee can lift |
| Down pressure | Clean texture without polishing | Medium | Max pressure with fine pads on smooth floors |
| Squeegee | Dry floor behind the machine | Rotate or replace edges on schedule | Worn blades leaving trails |
| Speed | Full recovery | Normal pace; slow on turns | Fast turns that throw water past the squeegee |
Squeegee blades and vacuum performance are covered in squeegees and vacuum motors and water recovery.
Worked example: the cost of a "splash extra"
A custodial team fills a 20 gal (about 76 L) walk-behind tank with a neutral cleaner labeled at 1 oz per gallon (about 7.8 mL per liter), so the correct dose is 20 oz. In practice, operators are pouring about 30 oz. That is 50 percent over label. Over six fills a week that is an extra 60 oz of concentrate; most leaves in recovery water, but a fraction stays as film, and in our estimate a few weeks of this often shows up in the cloth test. The fix is a marked measuring cup or wall dispenser plus a weekly rinse. Chemical spending also drops by roughly a third. See water and chemical use for broader context.
Wet floor procedures during scrubbing
Even a good auto scrubber leaves the floor briefly damp. Build these into every shift:
- Place wet floor signs at both ends of the area being scrubbed before starting, and move them with the work.
- Scrub in sections so a dry path stays open for foot traffic, or schedule scrubbing when traffic is lowest.
- Never leave a double-scrub (no pickup) area unattended.
- Remove signs once the floor is dry, or people learn to ignore them.
- Stop and pick up immediately if the machine starts leaving water. Do not finish the route first.
- Keep entrance matting clean and in place in wet weather, since rain and snow carry-in quickly overwhelms a clean floor.
Habits are the main variable, so operator training should include dilution, sign placement, and a squeegee check.
Frequently asked questions
What DCOF value is considered slip resistant?
ANSI A326.3 is commonly associated with a minimum wet DCOF of 0.42 for level interior floors expected to be walked on when wet. That figure is a flooring specification guideline measured under test conditions, not a guarantee of safety for a floor in service.
Does OSHA set a minimum coefficient of friction?
No. OSHA's walking-working surfaces rule at 29 CFR 1910.22 requires floors to be kept clean, orderly and, so far as practicable, dry and free of hazards, but it does not set a numerical friction value.
Why is my floor more slippery after it was scrubbed?
The most common cause is residue from overdosed or unsuitable chemical, followed by water left behind by a worn squeegee or clogged vacuum. Run clear-water rinse passes, measure the dilution, and inspect the squeegee.
Is an auto scrubber safer than a mop for slip risk?
Generally yes, because an auto scrubber recovers solution in the same pass and leaves the floor nearly dry. A mop leaves a wet film that takes minutes to dry and spreads dissolved soil around.
How often should I rinse a floor with clear water?
Many facilities run a clear-water pass weekly, and after every degreaser or heavy-duty clean. If the cloth residue test shows film, rinse more often and cut the chemical dose.