Tatami: The Rush-Grass Floor That Measures Every Room in Japan

Slide open the door of a traditional inn room in Japan and the first thing to arrive is a smell, faintly sweet and grassy, like a field after the cutting. The floor gives slightly underfoot, and the light falling across it looks warm and even. That surface is tatami, the woven rush-grass flooring that has shaped Japanese rooms, Japanese furniture and even the Japanese way of measuring space.

This guide explains what a tatami mat is made of, why room sizes in Japan are still counted in mats (jo), how the mats grew from a seat for nobles into a whole-floor covering, and the manners that go with them. It also covers what to expect in a ryokan (traditional inn), how mats are refreshed and repaired, and a short checklist for visitors who are about to step onto one.

What a Tatami Mat Is Made Of

A traditional tatami mat has three parts. The surface, called omote, is a tight weave of igusa (soft rush), a slender grass grown in flooded fields, stretched over a warp of hemp or cotton thread. The core, called doko, was historically made of rice straw sewn and pressed into a firm slab. Many modern mats use compressed wood chip board or foam layers instead, sometimes combined with straw. Along the two long sides runs a strip of cloth called heri (edging), which protects the woven ends and can be plain or patterned.

Making the surface takes a great deal of plant material. One industry source estimates that a single mat uses roughly 4,000 to 7,000 individual rush stems. Yatsushiro, in Kumamoto Prefecture on the island of Kyushu, is Japan's best known growing region for igusa, and its fields supply the large majority of the rush grown in the country. Fresh mats are pale green and carry a grassy fragrance. Both fade over a few weeks, and the colour mellows into a light golden brown that deepens with age. Many households treat that slow change as part of the pleasure of the material.

Counting Rooms in Jo

Ask how big a room is in Japan and the answer is often given in mats. The counter word is jo, so a six-mat room is rokujo and an eight-mat room is hachijo. Common sizes include 4.5 mats, 6 mats and 8 mats, and apartment listings, inn descriptions and tea houses all use these figures. The measure is a reminder that the mat came first and the room was designed around it, not the other way around.

A mat is not the same size everywhere. It is built on the old units of ken and shaku, and the length of those units varied by region. The Kyoto size (kyoma) measures about 1.91 by 0.955 metres, the Nagoya size (chukyoma) about 1.82 by 0.91 metres, and the Tokyo or Kanto size (edoma) about 1.76 by 0.88 metres. A mat is twice as long as it is wide, so two mats make a square, a unit called a tsubo of about 3.3 square metres. Because sizes differ, a six-mat room can be larger in Kyoto than in Tokyo, so check the dimensions if space matters to you.

For a sense of scale, a 4.5-mat room on the Nagoya standard is about 2.7 metres square. A six-mat room is about 3.6 by 2.7 metres, and an eight-mat room is about 3.6 metres square. Those proportions explain why even a modest tatami room feels calm: the grid of the mats gives the eye an easy rhythm to follow.

From Noble Seat to Whole-Floor Covering

The word tatami comes from the verb tatamu, meaning to fold or pile up, a clue that early mats were thin and could be put away. In the Heian period (794 to 1185), the palaces of the aristocracy had mostly wooden floors, and mats were laid out as seats or sleeping places for the highest ranking people rather than as a fitted floor.

During the Kamakura and Muromachi periods, a style of residence called shoin-zukuri developed for samurai and priests. In it, mats began to cover entire rooms, starting with small ones, and a fully matted room was known as a zashiki (a room spread out for sitting). Rules about who sat where shaped how the mats were arranged. Tatami reached ordinary households toward the end of the 17th century, and it then became a familiar feature of Japanese homes.

Today many new homes have just one tatami room, often kept as a multipurpose space for guests, naps or play, with wood or vinyl flooring elsewhere. Even so, the six-mat room remains a mental yardstick for what a comfortable room feels like.

Layouts and Lucky Patterns

Mats are rarely dropped into a room at random. In the arrangement called shugijiki (the auspicious layout), the corners where mats meet form a T shape and never a cross. This is the normal modern layout, and it often calls for a half mat, called hanjo, to make the pattern work around the edges of a room.

The older grid arrangement, where four mats meet at a single point in a plus shape, is called fushugijiki. In the Edo period (1603 to 1868) mats were rearranged depending on the occasion, and the grid layout was kept for certain solemn events. Today it is widely considered unlucky and avoided, so a floor laid in a T pattern will look familiar and settled to a Japanese guest.

Tea rooms follow their own logic. A chashitsu (tea room) is frequently a 4.5-mat space, and tea hosts sometimes use a three-quarter-size mat called daimedatami within it. The layout of the mats helps decide where the host kneels, where the guest of honour sits and how the utensils are carried in.

How to Behave on Tatami

The first rule is shoes. Footwear comes off at the genkan (entrance hall) of any Japanese home or inn, whether or not the room has tatami. Slippers go a step further: they are taken off before stepping onto the mats, because slippers wear down the rush. Socks or clean bare feet are the norm, and in a formal setting socks are the better choice.

Do not step on the heri. The cloth edges are easily damaged, and in some homes they carry family crests, so treading on them is considered rude. In the same spirit, the shikii (the wooden threshold rail between a corridor and a room) is not stepped on either. Walk across the mats and, once you reach your seat, sit on the zabuton (floor cushion). Avoid dragging cushions closer or standing on them with your feet.

At formal occasions you may be asked to kneel in seiza, with your seat resting on your heels, until the host invites everyone to relax. After that, folding your legs to one side or sitting cross-legged is usually welcome. Lift luggage and heavy objects rather than dragging them, since the weave scuffs more easily than a wooden floor.

Tatami in Ryokan Rooms

Tatami floors and futon bedding are two of the standard features of a ryokan, according to the Japan National Tourism Organization. Guests take off their shoes at the entrance, change into a yukata (a light cotton robe) if they wish, and step onto mats that are often described by their size, such as an eight-mat room. A low table and floor cushions usually stand in the middle of the room, and many rooms include a tokonoma, an alcove where a hanging scroll or a seasonal flower arrangement is displayed.

Because the mats are padded and slightly springy, bedding can go straight onto them. At many inns, staff lay out the futon in the evening, often while guests are at dinner, and fold them away in the morning so the room returns to its daytime shape. That quick change from sitting room to bedroom is one of the practical gifts of the tatami floor: no fixed furniture means the same space can serve many purposes.

Care, Repair and Renewal

Tatami is meant to be renewed, not replaced all at once. Specialists describe three levels of repair. In ura-gaeshi, the surface is flipped over and reattached to the same core with a new border, which is possible only while the other side is still in good condition and is commonly done a few years after installation. In omote-gae, the woven surface is replaced on the same core, often some years after the flip. A whole new mat is needed when the core has lost its bounce or has suffered damage from damp or insects, and the interval can be a decade or two depending on use.

Daily care is simple. Sweep or vacuum along the grain of the weave, wipe up spills at once with a dry cloth, and let air reach the mats. Avoid leaving heavy furniture or rugs in the same place for long periods, because the weave dents and the rush cannot breathe. Good ventilation matters in Japan's humid summers, which is why sliding doors and windows are often opened to air a tatami room.

Tips for Visitors

Before you step on any mat, check whether others have taken off their slippers. Carry a clean pair of socks in your bag, because many temples, inns and restaurants with raised tatami seating expect them. Place your shoes pointing toward the door or on the shelf provided, and put bags on a stool or in the alcove-side space the host suggests, not on the heri.

If kneeling is uncomfortable, ask politely for a low chair or a cushion, as hosts are used to guests of all ages and abilities. Stay away from the edges of the mats when you walk, lift your suitcase over the threshold, and keep drinks away from the weave. For visits to a ryokan, check the official site of the inn for check-in times and room types, and ask staff if you would like to see how the bedding is laid out.

Further Reading

Tatami on Wikipedia