Having worked in the building industry for a number of decades as a quantity
surveyor/cost consultant, much (but far from all) of it SI in both Canada
and the UK, millimetres makes the most sense. The centimetre is too big to
be used without having to use decimals of a centimere - in which case you
are down to the millimetre level. And when EVERYTHING on a drawing is in
millimetres, you don't need to express the units.
Does it make sense, you ask? Indeed it does. You very quickly get used to
expressing a dimension - even a large one - as something like "twenty six
five sixty two" , meaning 26 562 [mm], which can also be visualised as
26.562 m. If you hear construction workers on site, you will only ever hear
them talking like this - "just another 34 towards you" when positioning a
beam, say.
As for expressing slopes, these would be expressed as a ratio (1 in 50) or
as a percentage (2%). No units are shown, nor are they necessary.
As much as I quite like using centimetres for 'everyday' and sometimes
colloquial use of the metric system, centimetres in the construction
industry would be a disaster. The Brits, Canadians, South Africans and
Australians got it right when they elected to use ONLY the millimetre in
their respective construction industries. Does America have the sense to do
the same?
John F-L
----- Original Message -----
From: <a-bruie...@lycos.com>
To: "U.S. Metric Association" <usma@colostate.edu>
Sent: Friday, December 10, 2010 11:54 AM
Subject: [USMA:49114] Construction SI
First, is there an archive of this forum?
Second, I still do not get why the building industry choose to favor
millimeters vs. using centimeters. As a toolmaker, of course, millimeter
and micrometer is mostly used in the blueprints but millimeters in
construction? When a quarter inch is refereed to most often, as in a slope
of 1/4" to 12", in metric would simply be 2 cm to 1 m or 2%. Or using
8.25 cm vs. 82.5 mm for 3 1/4". When building homes and skyscrapers, mm,
do not make sense, to me.
I do not get their reasoning.
Id put my money on the sun and solar energy. What a source of power! I
hope we dont have to wait til oil and coal run out before we tackle that.
I wish I had a few more years left. -- Thomas Edison♽☯♑
