Their 'Blueprints' (aka: construction drawings) and buildings all had to be in whole numbers. And in my 45 years in Drafting and Engineering, and 41 years in the Commercial Construction 'bidness', I've never seen it.
Granted expecting something to actually be constructed to an 1/8" of inch is a bit much in 'the real world', but none the less that's how Architects and Structural Engineers have it on their design drawings (Blueprints).
And believe it or not, but sometimes - and getting more common now - us in the construction trades fight over 1/2" of space above the ceiling to install our work.
'Way back when' we joked that 'it wasn't Rocket Science'. Well... the tolerances are getting there as the taller a building is per floor height, the more it costs the owner. And those costs now are 'HUGH'.
The Romans also used a lot of concrete. For that matter, I agree with those who say the Egyptians used yet another form of concrete to build the Giza pyramids.
http://www.freerepublic.com/tag/davidovits/index