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RE: Floor Flatness

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	Robert Rollo wrote: 
> we have a client who desires to evaluate the flatness of an existing 
> concrete slab on grade floor and to measure any variations 
> periodically 
> i have seen reports that provided "micro-elevation" study that 
> provides a contour type mapping 
> for any evaluation it seems the tolerance should be tighter than 
> conventional survey practice 
> i am looking for information and equipment required regarding how to 
> conduct a slab elevation study with close tolerances. I am of the 
> understanding that a data collector is available that meets this 
> description. 

For at least the past ten years, floor flatness has been specified using
F-numbers, and compliance has been monitored using an electronic
dipstick device.  Both the F-number system and the dipsticks were
developed by the Face Companies of Norfolk, Virginia (757-624-2121 or  This technology is industry standard:  see ACI 117,
ACI 302.1R-89, ASTM E1155-87, and CAN/CSA A23.1-M90.  We have used it
repeatedly since 1990 with excellent results, both to evaluate the
adequacy of construction and to monitor movements over time.  Dipsticks
aren't cheap (more than $10,000).  However, as a structural engineer,
you shouldn't need to purchase them.  Just call your local construction
materials testing & inspection agency for this service.
Best regards,
Stan R. Caldwell, P.E.
Dallas, Texas
If it turns out to be a Cuban cigar,
then he should be impeached!