I think this is an interesting question but I'm struggling with how to make it fit the SE format, other than to ask for a reference that lists common dimensional lumber sizes in various countries. Does anyone have other ideas?
I guess the question I was really trying to ask was whether the metric universe had standardized a set of common off-the-shelf dimensions across countries that would serve as an equivalent of the American sizes for purposes of plan dimensions -- if an American shed is mostly 2x4's on 16" centers with 1/4" 4'x8' sheathing (some of those being real measurements and some nominal), is there a well-accepted set of metric dimensions would replace those elsewhere to build the equivalent shed, and are those subject to the same kind of inconsistency?
An answer of "almost; there are three such systems battling for dominance and they are..." or "not really, everyone has their own set of numbers influenced by their own historical construction practices" or "actually, there IS an international standard known as..." would then qualify as a clearly acceptable answer.
As I say, the real question is whether we can translate something between metric and American in any reasonable way, or if we just have to count on everyone making their own adjustments.
(Let's see, in stones/furlongs/fortnights that would be...)