Kui no Hi — Foundation Pile Day

What Is Kui no Hi (Foundation Pile Day)?

September 1st is "Kui no Hi," or Foundation Pile Day, in Japan. The date comes from a pun on the numbers 9 ("ku") and 1 ("i"), which together sound like "kui" (杭), the Japanese word for a foundation pile. It was established in 1993 by the East Japan Foundation Engineering Cooperative Association, a group of foundation construction contractors — named for the piles that anchor buildings, unrelated to the similarly-pronounced word for "eating."

Why Does a "Pile" Need Its Own Day?

Buildings, bridges, and other structures are supported by piles driven deep underground. Though invisible to the eye, this work forms the very foundation of a structure's safety. Pile-driving work often involves heavy machinery and elevated platforms, carrying real risk of workplace accidents — which is exactly why this anniversary also serves to raise safety awareness across the industry.

• Remembrance: honoring workers who lost their lives on foundation construction sites
• Safety promotion: promoting safe working practices in foundation engineering
• Safety convention: since 1997, a "Safety Convention" has been held alongside the annual memorial service

The Prayers Behind This Anniversary

Every September 1st since the day's founding, a memorial service has been held at Koyasan Tokyo Betsuin temple in Tokyo, where a Buddhist priest leads a moment of silence for workers who died on the job, and construction professionals renew their commitment to safety. It's an industry-specific anniversary that shines a light on work that usually happens entirely out of public view — underground.

Tips for Marking This Day

• Take a moment to imagine the foundation piles supporting the buildings you pass on your commute
• If you know someone in the construction industry, thank them for their everyday work
• Come up with your own pun playing on the double meaning of "kui"
• Read up on safety measures used at modern construction sites

To the People Who Support Our Lives From Unseen Places

The buildings and bridges we use every day without a second thought stand on countless piles driven deep into the earth — and on the skill and safety diligence of the people who put them there. Kui no Hi, on September 1st, is a day to turn our gratitude toward these unsung foundations of everyday life.