In Japan, people still talk about rooms as “six-tatami rooms” or “eight-tatami rooms.”
Today, these expressions are mainly used to describe room size. But traditionally, tatami were not simply something laid on the floor. In some Japanese homes, the dimensions of the tatami themselves were used as a basis for designing the room.
One well-known method was called tatami-wari.
For example, a six-tatami room could be planned so that six mats fit neatly inside it, with the structural posts placed around that space.
Once the size and arrangement of the tatami were set, the length and width of the room followed from them. The positions of posts, walls, fusuma sliding doors, and shoji screens could then be coordinated with the same dimensions.
This way of planning can be seen clearly in traditional Kyoto machiya townhouses. Because tatami and fittings were made to relatively consistent dimensions, damaged pieces could be replaced more easily or sometimes reused elsewhere.
In other words, tatami were not only floor coverings. They could also serve as a basic reference for determining the dimensions of a room.
That way of thinking still survives in everyday Japanese conversation.
If a friend says they have moved, someone might ask, “What is the layout like?” The answer could be something like, “A 1K with a six-tatami room,” or “Two eight-tatami rooms, plus a kitchen.”
For Japanese people, “six tatami” or “eight tatami” is more than an abstract number. Hearing it is often enough to form a rough mental picture of how large the room is.
However, not every traditional Japanese room was designed around tatami dimensions.
Alongside tatami-wari, in which the tatami dimensions were established first and the posts were arranged around them, there was also a method called hashira-wari. In that system, the spacing between the posts was decided first, and the tatami were made to fit the resulting space.
Tatami sizes themselves also varied by region and historical period.
So it would be inaccurate to assume that one tatami was exactly the same size everywhere in Japan, or that every traditional Japanese room was designed from the tatami outward.
Even so, tatami played an important role in how Japanese residential spaces were planned.
They became more than a way to describe floor area. Tatami could also act as a kind of measuring system that helped determine the shape and balance of the room itself.
References
- Kyoto City, materials on the preservation and succession of traditional Kyoto machiya, section on standardized modules
- Shimizu Hiroshi, “The Emergence and Spread of Tatami-Based Planning and Column Spacing in Early Modern Residential Architecture,” Journal of Architectural History
