All too often designers' specifications call for the same tolerances regardless of job conditions, the true and reasonable requirements of the job and the intended usage of the work. It seems obvious that a warehouse floor for cold storage does not demand the same accuracy as a hockey rink. What follows is a description of procedures developed by the author over the years, along with some suggestions of alternative ways of viewing tolerances so that our real work of construction can proceed on known and sound bases. Because of our work with ice rinks, examples and certain phrases will be specific to this usage; in general, the procedures and approach can be used for almost any situation. Hold a preconstruction meeting with all parties involved to review aspects of the work, such as access, equipment, temporary heat and labor. During this meeting, establish a durable bench mark in the field for all work and arrange for mandatory prior testing of design mix, materials, admixtures, and mixing plant equipment. Also establish with those present, and publish by follow-up meeting notes, exactly what step by step procedures will be followed for the installation of reinforcing, chairs, brine piping and inserts. During installation all of the procedures decided upon in the preconstruction conference are to be followed. After hardening of the concrete, a convenient grid is established, and survey shots of elevation recorded. It is recommended that the grid be not larger than 10 by 10 feet, and that a licensed independent surveyor perform the work. Moreover, readings should not be taken directly on the perimeter where irregularities may not be representative of the actual slab condition in the area. The standard deviation, S, of the normal curve calculated should then form the basis of determining compliance with the tolerances required. A slab requiring relatively low tolerance control might use, by specification, (1.0)S = one-eighth of an inch. This would mean that about two-thirds of all of the points have to be within the specified tolerance limits of one-eighth of an inch. A slab under high tolerance control might have specified (1.5)S = one-eighth inch, which would mean the 87 percent of all of the points would have to be within the specified tolerance of one-eighth of an inch.