Metrication Update

Two examples of metrication crossed my desk recently, demonstrating opposing approaches to implementing metric units in the building products industry.

1. One of my clients is converting its sales literature from inch-pound to metric (with inch-pound units also shown in parentheses).

#11 1-3/8" dia.
2. The Concrete Reinforcing Steel Institute (CRSI), reversing its decade-old endorsement of a soft-conversion to metric, now urges its members to use inch-denominated size markings.

The various approaches represent the different market conditions confronting each organization.

In the first instance, the US-based firm is aggressively moving into international markets and needs to speak the lingua franca used for most of the world's construction. The change will not harm domestic sales, since the company uses digital-fabrication to make bespoke parts without regard for the designer's system of measurement.

CRSI, on the other hand, focuses on regional and national promotion. As a commodity product, little quantities of rebar is exported. The industry began marking its product in nominal metric sizes when it looked like the Federal government was serious about enforcing a 1991 Presidential Executive Order mandating metrication. However, the Federal Highway Administration (FWA) retracted the requirement in 2008, and most building construction in the US remains firmly inch-pound. (The primary exceptions Government agencies such as the Department of Defense.)

Traditional rebar diameters are stated in 1/8 inch increments; #3 = 3/8 in. diameter, #12 = 12/8 in. = 1.5 in. These units just make sense when constructing a 1 ft. thick wall with 3/4 inch concrete coverage over rebar that must be spaced to allow passage of 1-1/2 in. dia. coarse aggregate. In CRSI's soft conversion, these correspond to #10 (9.525 mm) and #40 (38.1 mm) respectively. Soft conversion reduce the cost of producers, but frustrated everyone else. Builders using inch-pound had to convert sizes to traditional nomenclature to calculate positioning. And fractions of a millimeter confounded those used to using real metric sizes, where #30 bars have 30 mm dia.

Many US industry sectors are now firmly metricated. (When was the last time you bought a fifth of whiskey?) Yet it is unlikely that there will be a comprehensive countrywide construction conversion anytime in the foreseeable future.

Until then, each building product manufacturer will have to "weigh and measure" whether and when to embrace metric based on their unique marketing "metrics."

By the way:

"Metrication" is term for adopting metric measurements.
"Metrification" is term for using poetic meter.