One of the requirements to protect the casket after burial is the outer burial container or sometimes called the burial vault. Vaults come in many different materials, the prevalent one being concrete. Other materials include steel and now even plastic vaults are available. The material I am most familiar with is concrete, so for the purposes of discussion I will only be covering vaults made of concrete.
Pricing of concrete burial vaults is largely determined by the materials of which they are made The thickness of the concrete, the addition of plastic being bonded to the concrete on the inside, and then a metal being bonded to the plastic present a multi-layered protection with each layer adding more cost to the product. Fortunately the consumer can purchase vaults with various levels of protection.
Over the years the burial vault has evolved into two basic types: one that seals at the bottom, or one that seals at the top. The one that seals at the bottom, sometimes called an air seal or a bottom seal, has a bottom placed into the grave and the casket is lowered onto it and then a box is lowered over the casket, keeps the casket dry by working on the same principle as when you turn a cup over and place it under water. An air bubble is formed and as long as the air is trapped there, water will not rush in. The vault that seals at the top has has a bottom box shaped piece that is lowered into the grave prior to the casket being lowered into it. Once the top is placed on the vault, a sealing agent adheres the two parts together.
The selection of which burial vault to use is a largely personal decision. Both varieties are designed to keep the elements from the casket inside, and to keep the cemetery grounds level. In all states it is not a law that a vault must be used. Most cemeteries require their use to maintain the beauty of the burial grounds.
Top Seal Vault Photo Courtesy: The Tribute Companies http://www.tributeinc.com