It's not uncommon for us to use 1:15, 1:20, 1:30, 1:40, 1:50, 1:60, 1:80,
1:100, 1:150, 1:200, 1:300, etc... & some of our old drawing that were done
by hand are 1:25. 1:150 is a multiple of 1:30 (think engineering &
surveying using decimal feet). On the other hand I've never heard of a floor
plan done to that scale.