Why bury posts beneath the frost line?

Burying posts beneath the frost line is essential to prevent movement caused by frost heave, which occurs when soil freezes and expands. If posts are not placed below this line, they can shift or crack as the ground freezes and thaws, compromising the stability of structures like fences and decks. This practice ensures a more durable and long-lasting installation, reducing the need for frequent repairs or adjustments. Proper depth varies by region, depending on local climate conditions.