Most of tatami is used in washitsu in Japan. Obviously, the wood floor can also be used in Japan, but Bright Planet recommends Tatami
In traditional domestic architecture the Japanese characteristically use wooden panels and paper shutters as the chief building materials for the exterior, and fixed or sliding panels of wood and rice paper as dividers in the interior. Such dividers offer the convenience of flexibility in the arrangement of interior spaces. This miniature room is the zashiki, or main room, of the traditional Japanese home, and also the adjoining room customarily used by the mistress of the house. Essential elements of the main room are the two recessed areas at the back. The alcove to the left houses artistically arranged wall cabinets and shelves for art objects. The alcove to the right is traditionally used to display a single work of art—a scroll or vase—chosen to be enjoyed for a day from a stock of such treasures kept in a fireproof storeroom. The floor of the main room is always covered with tatami, or straw mats, each of which measures about three by six feet and is bound with cotton borders.