The engineer estimates the decrease in floor flatness with time, then specifies an initial FF that later drops to the value needed by the floorcovering installer. Making the estimate is not easy because the amount of curling varies with the concrete properties and service environment. Also, the higher the initial specified FF, the greater the percentage loss in floor flatness for a given amount of curling. Thus, the concrete contractor might be paid more to produce an initially flatter floor that does not benefit the floorcovering installer because the amount of curling exceeds that anticipated by the engineer.
