What Happens to a Casket Underground?

It’s a question many people wonder about privately but rarely ask out loud: what actually happens to a casket once it’s underground?

Why do cemeteries require a vault or liner?

Many cemeteries require an outer burial container, a vault or a liner, around the casket. Its purpose is often misunderstood - it’s not primarily about preserving the body. The Federal Trade Commission says the purpose of a vault or liner is to prevent the ground from caving in as the casket deteriorates over time. A cemetery with hundreds or thousands of graves needs a level, mowable surface over the long term. The Louisiana Cemetery Board says the same: a container helps keep the ground from settling after a burial and makes mowing and maintenance easier.

Does the law require a vault or liner?

No. The FTC says outer burial containers are not required by state law anywhere in the U.S., though many cemeteries require them, and funeral providers may not tell you otherwise. A funeral home must give you a written price list for the containers it sells. Not all cemeteries have the requirement, so ask the cemetery, and see our guide on green and natural burial for options without one.

Does a vault stop decomposition?

No. The FTC says neither grave liners nor burial vaults are designed to prevent the eventual decomposition of human remains. Decomposition is a natural, expected part of burial - over time, both the casket and its contents gradually break down, regardless of the vault surrounding them.

How long does a casket typically last underground?

We did not find authoritative timelines, and the right answer is that it varies with the casket’s materials, the soil, and moisture. What the FTC does say is that no process or product has been devised to preserve a body in the grave indefinitely, and that no casket, regardless of its qualities or cost, will preserve a body forever. Some advertisements for caskets or containers claim they will delay decomposition for a long time. The FTC says no casket or container can do that and that the Funeral Rule prohibits claims that it can, so be skeptical of such claims when comparing prices.

Is this something families should feel uneasy about?

This isn’t something cemeteries or funeral homes treat as unusual or unsettling - it’s simply a matter-of-fact part of how burial works. Many families never think to ask, not because the answer is upsetting, but because it simply doesn’t occur to them as a question. Understanding it as an ordinary, expected process can make it easier to ask directly if it’s something you’re curious about. The same is true of the skeleton specifically, which lasts far longer than the casket itself - see our guide on what actually happens to your bones after burial for that fuller timeline.

Specific timelines vary by material, soil conditions, and vault type - a funeral home or cemetery can offer more specific guidance.