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Re: Levelness Specification

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An F-number specification isn't applicable because the standard test method for measuring flatness and levelness (ASTM E1155) requires the minimum area for the test section to be 320 sq ft. ACI 117 also requires the measurement to be made within 72 hours after completion of finishing. The flatness and levelness may change after that as mentioned previously.

Is the chiller manufacturer actually interested in flatness, as opposed to levelness? The floor requirements for a CT scanner installation typically require a maximum gap of 1/8 in. under a 10-ft straightedge resting on high points within the area where the leveling pads are positioned. They sometimes call this a levelness measurement, but it's actually flatness that's being measured.

See Section 4.8.6 of ACI 117-06 for a straightedge measurement protocol. That document says the straightedge measurement method is not sufficiently precise to evaluate floors to a gap less than 1/4 in. in 10 ft, But for the small area you've described it's probably precise enough and would be the simplest way to specify flatness. It doesn't measure levelness, however.

Ward R. Malisch



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