Nominal

I got cylindrical forms for the post footings. It was recommended someplace I was reading (which doesn’t say much, because everything I read had slightly different recommendations, from how wide a hole to how deep to how high the concrete should come), and it made a certain amount of sense given our freeze-thaw cycle here.

The forms, which come in 4′ lengths, are measured by diameter. We got the “10 inch nominal” ones.

nominal \Nom”i*nal\, a.
[L. nominalis, fr. nomen, nominis, name.]
1. Of or pertaining to a name or names; having to do with the literal meaning of a word; verbal; as, a nominal definition.
2. Existing in name only; not real; as, a nominal difference.

I think this was meant as in defn. 2, since there was, in teeny-tiny print, the note “+/- 0.5 inches.” That means they could (and did) run from 9.5″ to 10.5,” which works out to 57 sq. in. to 87 sq. in. Or, in other words, the smaller tubes were 2/3 the area in cross-section of the larger tubes.

Which is why, I suppose, they could nest up to three 10″ (nominal) tubes inside of each other. And why some tubes were very difficult to fit into the 10″ (nominal) holes we bored, and why were way too easy.

As I noted later in the day, clearly this is not rocket science. Something useful to remember when sweating over the slightest variation.