Underneath the surface mat is the inner core of the tatami. It's about 5.5 centimetres thick. Traditionally, this is made entirely from rice straw, which offers the perfect degree of firmness, while allowing the air to pass through it.
畳表の下にあるのが畳床です。厚さはおよそ5.5センチメートル。伝統的にはすべて稲藁で作られており、適度な強度と通気性を兼ね備えています。