From the JList newsletter.... http://www.jlist.com
When talking about the sizes of rooms in Japan, you never use square meters, but instead refer to the number of tatami mats the room contains (or would contain, if it were a tatami room). Tatami mats are standard-sized rectangular mats made of straw, that are supposed to be the correct space for one adult to sleep. A 6-jo room ("jo" is the Chinese pronunciation for the "tatami" character) is average sized; poor college students have to live in a 4-jo-han (or a small apartment that's just 4 1/2 tatami mats in size). When you buy land, you measure it in "tsubo," an area of measurement that's conveniently equal to two tatami mats. Thus if you have 50 "tsubo" of land you can picture it as 100 tatami mats in size. When you've been in Japan as long as I have, it becomes quite easy to do.
Ah so. I like reading snippets from this newsletter. In Japan nobody would even think of purchasing a used house to live in. It seems it's the cutom to purchase a house for the land, knock the house down and build a new one.