Height determining instrument for poured floors, and method

The present invention relates to a height-indicating instrument and method enabling the production of poured cementitious floors upon uneven sub flooring, the poured flooring having a flat, level top surface and a thickness not less than a predetermined minimum thickness. A height indicating instrument useful for preparing flat and level cementitious floors over an uneven sub floor. The instrument includes first and second rod assemblies, the first having a foot engagable with the surface of a sub floor and the second assembly operatively attached to and moveable axially with respect to the first assembly. The second assembly includes a height indicator to indicate the desired underlayment height, and carries a laser beam detector. A laser beam generator generates a horizontal laser beam detectable by the laser beam detector. Vertical movement of the second rod assembly with respect to the first rod assembly to horizontally align the detector with the generator simultaneously moves the height indicator to adjust elevation of the latter with respect to the foot. At a plurality of locations on the uneven sub floor, slurry is poured until the slurry rises into contact with the height indicator at each such location.