3" TYPICAL

Posted: 05-08-08 (MrHawk)

A few weeks out of the C.R.S.I. training course, this was 1983, I was working on one of the first few projects that the fabricator I worked for had entrusted to me. Only a couple of weeks before, I learned what rebar is. I was as lost as anyone could be in this strange, or should I say alien, industry. On this project, as a conscientious trainee, I was concerned because the engineer only provided one note about clearances. (Where my memory serves me, I'll defer. When it does not, I'll embellish.)

At the bottom of a grade beam section was a dimension, which denoted 3" CLR, TYPICAL. Of course, this clearance indicated the distance from the bottom of the grade beam to the bottom of the beam stirrup. But, what about the clearance to the sides and top of the stirrup? For that matter, what about the clearances to the rebar in the slab on grade? What to do?

My employer had a few experienced detailers; two with years under their belt, and one with months under his. I happened to ask Mr. Months.

With the hopes of clarifying things, I asked Mr. Months, who, without malice and with only the best of intentions responded, "It says typical." Essentially, 3" clear typical, meant 3" clear everywhere.!

You know where I'm going here--yes, I dutifully used 3" cover everywhere on the foundation. Back then, as is (most of the time) the case today, the 30 day approval process supplied me with a stamped, "APPROVED AS NOTED" drawing. There was a couple of red marks, neither of which addressed clearances. I fixed what the engineer noted, generated a material list, which was done manually at the time, and reinforcing steel was fabricated. A few day reprieve passed between the fabbing and delivery--then, ring, ring... The phone calls began. I'll spare you the details, for I'm sure you can figure out where things went from that point.

My ego was damaged beyond repair, my employer ate the cost of fixing the errors, the job was delayed, and I wondered if I was right for rebar detailing. Mr. Months was unscathed, and I learned a valuable lesson about what 'typical' really means in the construction industry.

TYPICAL = Conforming to the context of the note -- except where otherwise might be conscrued as different from the note; usually applying in conditions where no reference to typicality is explicit -- or as generally determined by the contractor, and or, the engineer.

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