The basic structure of tatami is simple: it consists of three main parts—the Filling (Toko), the Surface (Omote), and the Border (Heri).
While this is a straightforward overview, tatami craftsmanship involves many detailed techniques and material choices.
Today, newer materials also exist, but the core concept has remained unchanged for centuries.
Glossary
- Filling (Toko) :
- The core/base of a tatami.
- Surface (Omote) :
- The woven top layer.
- Border (Heri) :
- The fabric edge.
- Igusa (Rush) :
- Natural rush used to Warp yarns (threads) the surface.
From here on, this page uses the shorter forms: Filling / Omote / Border / Igusa.
1 Tatami-toko(filling)
Traditionally, the Filling was made as Wara-toko—a core composed of many layers of 100% natural rice straw. Today, depending on the purpose and installation needs, Filling can also be made with lightweight building materials, such as polystyrene foam combined with boards.
Wara-toko (Natural straw filling)
Natural straw Filling is the classic option and has been used for centuries. A thick stack—starting at around 40 cm—can be compressed under extremely high pressure to roughly 5 cm.
Key benefits include excellent humidity control, fire resistance, thermal insulation, durability, and resilience. It also offers a distinctive, comfortable feel underfoot.
For example, the Hōjō at Daitoku-ji Temple (a National Treasure) has 112 tatami with inscriptions dating back to 1673, illustrating how well-made tatami can last for generations.
More about Wara-tokoSandwich filling (Polystyrene Foam)
This type of Filling uses polystyrene foam sandwiched between layers of straw. It feels closer to natural straw than fully synthetic options and is lighter than a fully natural base. It also tends to perform well in humid conditions.
Because Filling grades vary, the straw materials used also differ. Sandwich Filling typically uses crushed straw, while higher-grade natural Filling uses longer straw fibers, which improves strength and overall quality.
Kenzai-toko (Building-Material Filling / Non-Natural)
There are several types of non-natural Filling, including compressed wood-chip boards (insulation boards), board-and-foam combinations, and all-board constructions.
These options are generally more affordable and lightweight, with good insulation and moisture resistance. They also tend to be less attractive to mites and insects. On the other hand, they usually feel firmer underfoot and may be less durable than natural straw Filling.
2 Tatami-omote(surface)
Omote is graded. The highest grade of omote is generally found in scared places like shrines and temples, wealthy homes, and important spaces.
To gain a premium grade the omote has to be made from igusa of a certain length, quality and Warp yarns. High quality omote has four hemp strings, two at each Warp yarns, binding the igusa together, and is generally made of two mats weaved together in the centre; this forms a thick, strong mat. High quality Igusa used in these mats is only harvested once a year.
The most commonly used omote in Japanese homes and for international clients is the high to mid grades; this omote is still a premium product but is more readily available. The lower grades vary. There are still good products at this level. These mats do tend to have a shorter life span. This omote is good for areas of high use, where mats will need to be resurfaced more regularly. While omote vary in quality and look, the lowest grade Japanese omote is much higher quality than any other overseas product.
Effect of Igusa
Tatami made with Igusa can contribute to a more comfortable indoor environment—supporting factors such as humidity balance, acoustics, and thermal insulation. As seasons change, Omote can absorb and release moisture, helping regulate humidity and temperature in the space. These qualities support a calm, healthy living environment.
Imported Products and Japanese-Made
In recent years, imported Omote has become more widely available, mainly because it is easier to source and less costly to produce. While imported products can meet certain needs, there are important differences compared with Japanese-made tatami.
- Harvest timing: Imported Igusa is often harvested earlier. In Japan, Igusa is typically harvested at full maturity, which supports long-term durability.
- Drying methods: Japanese-made tatami commonly uses Igusa that is slowly dried at lower temperatures, preserving natural resilience and a smooth surface. Faster, higher-temperature drying can reduce elasticity and change texture.
- Selection and grading: In Japan, Igusa is carefully selected and graded at the farm level for consistent color and quality. Imported products may vary more, and some may use color adjustment treatments that can affect fragrance and how the material ages.
Imported products continue to improve. However, Japanese-made tatami remains valued for mature materials, careful processing, and long-term performance—qualities rooted in traditional craftsmanship.
(Lower) Imported Omote
Warp yarns (threads)
Igusa is woven using warp yarns (the lengthwise threads), typically made from hemp or cotton.
The choice of warp yarn affects durability: stronger yarns allow for a tighter weave, which increases thickness and strength and also influences the feel underfoot.
Hemp is generally the strongest option.
Bingo (top quality) double hemp
Bingo (second grade – still classifies above other omote) Cotton and hemp
Yume-omote / cotton and linen
Asa-biki / single hemp
Imported / double cotton
Imported / single cotton
Range of Omote
There are various kinds of omote for different needs: Meseki-omote, woven finer than usual; Ryukyu-omote, made from stronger igusa called Shitto-i; omote made of chemical fiber or paper, along with others.
※(Left picture) Ryuku-I (Shitto-i)
3 Tatami-heri(border)
In the past, Border was often made from cotton or hemp, but synthetic fibers are common today. Synthetic materials are generally more affordable and durable, while natural fibers tend to offer a more refined look and feel. High-grade Border often uses hemp.
Border can be a simple solid color or feature a wide variety of patterns, including styles used for temples and tokonoma (alcove).
More about Heri(border)About Kamachi
The shorter sides of a tatami mat are called kamachi. If the Filling is simply wrapped without proper reinforcement, the corners can become damaged and may swell over time.
Historically, a wooden kamachi-ita (kamachi board) was hand-sewn into place. Today it can also be sewn by machine, but some still prefer traditional hand-sewn wooden kamachi for its finish and perceived quality.
(kamachi board)
Materials available: wood, plastic (standard), and paper.
