Slip Resistance for Concrete Flooring

In the interest of developing a scientific way to determine how slippery a surface is, measurements of slip resistance have been developed. In the United States, slip resistance is determined by measuring the static coefficient of friction (SCOF) of a surface. SCOF is defined as the force required to start relative motion between an object and the surface it is resting on. Europe and Australia have used measurements of the dynamic coefficient of friction — the force required to keep a sliding object in motion once sliding has begun — but these measurements have not gained acceptance in this country.

SCOF can be measured using a variety of instruments, each of which may cost thousands of dollars, and no single one is universally accepted among experts. This controversy poses a difficulty for the flooring contractor that just wants to lay safe flooring. Each contractor is well advised to research the methods before choosing an instrument to invest in or a test lab to use.

In the United States, the most widely accepted and best-known evaluator of slip resistance measurement methods is the American Society for Testing and Materials (ASTM). The society publishes standards describing each instrument for determining SCOF, how it is to be used, and the results of scientific testing to determine how valid it is. ASTM has indicated that most methods can be used only for dry surfaces because liquid sandwiched between two resting surfaces interferes with accurate measurement by opposing the force needed to initiate motion. This is unfortunate, because most slips occur on wet surfaces, which are usually more slippery than dry surfaces.