There are two considerations owners, architects and engineers should bear in mind when they prepare plans and specifications for concrete floors:

  1. The present American Concrete Institute standard tolerances for floor flatness are too tight for most jobs and are usually not attainable on those jobs.
  2. For many years contractors have been literally forced to bid on specifications that include tolerances that cannot be attained by practices that are justifiable for the job.

Small flatness tolerances are needed in relatively few situations. Examples are:

  1. Narrow-aisle, high-bay warehouses that require use of high-stacking forklift trucks.
  2. Specific limited areas within building where special material handling equipment requires close tolerances.
  3. On elevated slabs where close-dimensioned prefabricated building units will be used. For such jobs the specifications should call for a so-called superflat floor.

Specifications should hold the contractor or concrete subcontractor responsible for meeting the flatness tolerances only at the time the floor has been placed and finished, not when it is turned over to the owner.