Why do I need a burial vault?
In most areas of the United States and Canada, a cemetery requires the casket to be enclosed within a burial vault or grave liner. There are vast differences in these two products. By definition a burial vault is a lined and sealed unit that is specifically engineered to support the weight of the earth above the grave as well as the heavy equipment that passes over it.
Concrete becomes stronger as it continues to cure after being placed in the ground; so a vault properly buried years ago could actually be stronger today.