Namako-kabe (なまこ壁) is a wall design used widely on a vernacular houses, particularly on storehouses. This wall finishing protected buildings from fire and water damage. They are easily distinguished by their white grid pattern on black slate.

The white clay joints, a few centimeters wide with rounded tops, reminded people of the Namako sea cucumber. They quickly became known as Namako-kabe due to this resemblance.

— History

Namako walls were introduced during the late-Edo and Meiji periods when many Western ideas were being inegrated into Japanese society. It can be seen as to resemble Western bricks-and-mortar techiniques.

They are most common on the Western side of Japan, prominently in the San'in and Sanyō regions. During the 19th century, to the east, they became more common in the Izu region.