Slip Resistance Testing of Coated Floors

Slip resistance testing evaluates how much friction a walking surface provides, so that the risk of slipping can be judged and compared. For coated floors, decks, ramps and stairs, results are usually reported as a coefficient of friction (COF) measured with a tribometer, or as a pendulum test value (PTV) measured with a swinging pendulum tester. Testing is used during product development, specification, commissioning and maintenance of anti-slip coatings and resinous floors.

Basic concepts

Coefficient of friction

The coefficient of friction is the ratio of the force needed to slide one surface over another to the force pressing them together. Two forms are discussed:

• Static COF is the force needed to start movement.
• Dynamic COF is the force needed to keep movement going.

Modern floor safety standards in North America focus on dynamic COF, especially when the surface is wet.

Wet versus dry testing

Most slips happen on contaminated surfaces. A floor that grips well when dry may be slippery when wet, oily or dusty. Testing under the contaminant conditions expected in service gives more meaningful results.

Common test methods

ANSI A326.3

ANSI A326.3 is a North American standard for measuring the wet dynamic coefficient of friction of hard surface flooring materials using a specified tribometer and test slider. It provides guidance on product use categories, such as interior level wet areas and exterior areas. It replaced older reliance on static COF methods for ceramic tile and is often applied by reference to other hard flooring.

Pendulum test

The pendulum tester swings a rubber slider across the surface and measures energy loss. It is standardized in BS 7976, EN 16165 and AS 4586, among others, and is widely used in the UK, Europe and Australia. Results are reported as PTV. The pendulum is portable and can be used on site in wet conditions.

Ramp tests

Ramp tests, such as DIN 51130 and DIN 51097, have a person walk on a sample mounted on a ramp whose angle increases until slipping occurs. They are laboratory tests that classify surfaces into R or A/B/C classes. They are common in Europe for product classification.

Withdrawn and older methods

Older static COF methods, such as ASTM C1028 and drag-sled tests, appear in historic specifications but have been withdrawn or are no longer recommended because of repeatability concerns. Some legacy guidance cited a COF of 0.5 as a benchmark; current practice is to use the thresholds and categories in the standard being applied rather than a single rule-of-thumb number.

Factors that influence slip resistance of coated floors

• Surface texture. Broadcast aggregate, texture additives, and the coating’s own profile provide grip. See broadcast flooring systems.
• Aggregate type and size. Aluminum oxide, silica sand, polymer beads and glass grit give different textures and wear behavior.
• Topcoat thickness. A heavy topcoat over broadcast aggregate can “drown” the texture and reduce grip.
• Wear. Traffic smooths texture over time. Periodic retesting shows whether grip is falling.
• Contaminants. Water, oils, food residues and dust all change friction.
• Cleaning practice. Some cleaners leave residues that reduce grip; others restore it.
• Footwear. Real slip risk depends on footwear as well as the floor.

Designing a slip-resistant coated floor

1. Identify the use and contaminants. A commercial kitchen, a pool deck and an office corridor need different textures.
2. Choose a system with test data. Ask the manufacturer for tested values on the actual system, with the method named.
3. Prepare sample boards. Build samples with the intended aggregate and topcoat thickness, then test or evaluate them.
4. Balance grip and cleanability. Very aggressive textures can be hard to clean and uncomfortable to walk on.
5. Plan for maintenance. Specify the cleaning method and retest schedule.

Avoid stating a slip rating for a coating system unless test data supports it for that system.

Testing on site

Site testing documents the as-installed condition. Good practice includes:

• Testing in representative locations, including wet areas, ramps and entrances.
• Recording the method, instrument, slider type, surface condition, contaminant and temperature.
• Calibrating instruments as the standard requires.
• Retesting after maintenance or when complaints arise.

Relationship to other coating tests

Slip resistance is related to, but distinct from, abrasion and hardness testing, which predicts how quickly texture wears away. Gloss and color measurement does not predict slip resistance; a matte floor is not necessarily grippy.

Key terms

• Coefficient of friction (COF). A dimensionless ratio of friction force to normal force between a shoe or slider and the surface.
• Static COF. The friction that must be overcome to start movement.
• Dynamic COF. The friction during sliding, which is the basis of ANSI A326.3 and many tribometer methods.
• Pendulum test value (PTV). The result of a pendulum test, widely used in the United Kingdom and Australia.
• Slider material. The rubber pad used in testing, which must match the standard because it strongly affects results.
• Contaminant. Water, oil or other material applied to simulate real conditions.

Frequently asked questions

Does a textured coating guarantee a safe floor?

No. Slip risk depends on texture, contaminants, footwear, maintenance and human factors. Testing reduces uncertainty but does not remove risk.

How often should floors be retested?

There is no single rule. High-traffic or wet areas benefit from regular checks, and testing after refinishing or changes in cleaning is sensible.

Can a slippery coated floor be fixed without recoating?

Sometimes. Deep cleaning to remove residues may help. Otherwise, a textured topcoat or anti-slip treatment applied according to the manufacturer’s instructions is typical.

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