The most common mistakes on buildings are not calculating out live and dead loads of buildings.
Lets look a living room, it has a large rug, 1 large couch, 1 love seat, 2 chairs an old style piano as well as some tables lamps books etc. the items listed is called live load because it can move into different parts of the house.
Lets look at the floor, it consists of oak wood floor, and under this floor is a sub floor. These to floors are called dead load they cannot move.
The room size is 144 sq. feet with a total live working load of 5760# we have over 2200# of furnishings lets say its Christmas and time for pictures 20 Light weight people have just overload the floor system.
But that was just for a couple of minutes well lets look at the dining room for 2 hours you have overload the floor system in there.
Lets look at the office paper is a lot heaver than people, a small 2 draw filing cabinet can hold up 960# of paper + he cabinet.
Most people have a few large filing cabinets as well as desks and chairs, printers, copiers.
The minimum for home construction is 40 live load, and for an office is 150# live load so by putting an office on a wood floor system is wool fully over taxing flooring system.
Look a baby grand piano it ways over 1000# setting on 3 points on the floor than add people around the piano and again you over taxed the floor.
Now your loads and what you are going to use the rooms for before building house.