Units of measure in specifications are of two types:
- Measurements, which can be exact or nominal
- Sizes, which, like shoe sizes, may sometimes have only the vaguest relationship to the actual measurements
Sizes are usually standardized in a reference document, usually the same document that standardizes other features of the relevant product.
The U.S. still uses inch-pound dimensional systems even though use of SI ("metric") has been mandated by the federal government for government projects for many years. The three documents listed are those that BSD recommends for standardization of units of measurement with international systems. These documents should be used in the order presented -- the first is the most fundamental, while the other two address the construction industry and construction documents in particular.
Both inch-pound and SI units are included in SpecLink, with a "switch" to change which is included, but if you add dimensional requirements and wish to have those swtich too, you'll need to make the conversions yourself.
IEEE/ASTM SI-10, Standard for Use of the International System of Units (SI): The Modern Metric System
From ASTM International, www.astm.org
This is a voluntary standard for the unified American National Standard for metric units, developed from previous ASTM E 380 and IEEE Std 268. It conforms to latest international standards. For those unfamiliar with SI, this is a valuable reference work.Metric Guide for Federal Construction
Published by the National Institute of Building Sciences (NIBS), www.nibs.org.
This document is the guide prepared for federal government agencies and, as such, is what those agencies expect their A/E contractors to follow. It defines preferred units and standard degrees of precision, in the principal design disciplines, along with drawing practices. There is not much on specs — it would need to be supplemented for many subjects.
NIBS also publishes several other guides to construction metrication.
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