The thing is, wire gagues, pipe sizes, 2x4's, and other nominal sizes don't change in metric construction.
Instead of 24" or 18" stud spacing, you have 600mm or 400mm stud spacing, and instead of 4x8 drywall or plywood, you have 1200x2400mm plywood (so that it fits nicely on your 600mm or 400mm stud spacing), of the same thickness. The modular stuff is about the only thing that actually has to change size.
And its easier in many ways too - "For example, which has the greater thermal capacity, a 22 million Btu/hr boiler or a 1000 ton chiller? Using metric units, you can tell instantly: the boiler is 6.4MW and the chiller is 3.5MW."
http://www.nibs.org/poster2.PDFI know, I'm just being a curmudgeon.
P.S. Sorry to read where you had to grow up. :-)