The distinctive and pleasant smell of a Japanese room comes from the tatami. These rectangular padded straw-and-rush mats are used for flooring, providing a soft surface on which to sit on cushions and sleep on Japanese futons. Tatami come in an aspect ratio of 2 to 1 and have varying sizes depending on the region in which they are made: Tokyo tatami mats are smaller than those in Kyoto for example. They continue to be popular in modern Japanese homes, where one room or more may be covered in tatami, and room sizes are often still quoted in terms of the number of tatami mats that would cover the floor.
As mentioned Tatami mats are made from rush and cloth. The rush is woven in, and cloth is used to cover the woven ends. A traditional Japanese room, or washitsu (和室), always uses tatami as flooring. New tatami mats are green, but as they grow older, they yellow. Tatami mats are made to fit the room, not the other way round. So while there is a standard size, this is not the only option. There are 4 standard sizes; Kyouma (京間), Chuukyouma (中京間), Edoma (江戸間), and Danchima (団地間).
Kumamoto, Hiroshima, Okayama, Fukuoka, and Kouchi are famous for growing the rush, or igusa (イグサ) the mats are woven from. To make one tatami mat, 4000 to 7000 pieces of rush are used. Today, machines can complete the weaving process in about a hour and half.
There are two ways of placing tatami mats (see illustration above). Shyugi Shiki (祝儀敷き) is the most popular way done in normal households. The Tatami mats are placed in a way that the 4 corners of the Tatami don’t gather in one spot.
Fushyugi Shiki (不祝儀敷き) is used for unlucky events such as funerals. It is a custom in order to avoid the bad luck.
It is customary to remove your shoes in Japan when entering a room with hardwood flooring or tatami mats. Shoes are a big no-no for tatami mats, since they damage the woven rush.
In a tatami sitting room, there are certain ways to sit that are considered good manners, for example when guests are visiting. Cross-legged is considered more casual. Seiza (正座) is the most formal way to sit on tatami mats. You bend your legs and sit on them, with your feet crossed under your bottom.