Bank vault

A bank vault is a secure room used by banks to store and protect valuables, cash, and important documents. Modern bank vaults are typically made of reinforced concrete and steel, with complex locking mechanisms and security systems. This article covers the design, construction, and security features of bank vaults.

Unlike safes, vaults are an integral part of the building within which they are built, using armored walls and a tightly fashioned door closed with a complex lock.

Historically, strongrooms were built in the basements of banks where the ceilings were vaulted, hence the name. Modern bank vaults typically contain many safe deposit boxes, as well as places for teller cash drawers and other valuable assets of the bank or its customers. They are also common in other buildings where valuables are kept such as post offices, grand hotels, rare book libraries and certain government ministries.

Vault technology developed in a type of arms race with bank robbers. As burglars came up with new ways to break into vaults, vault makers found new ways to foil them. Modern vaults may be armed with a wide array of alarms and anti-theft devices. Some 19th and early 20th century vaults were built so well that today they are difficult to destroy, even with specialized demolition equipment. These older vaults were typically made with steel-reinforced concrete. The walls were usually at least 1 ft (0.3 m) thick, and the door itself was typically 3.5 ft (1.1 m) thick. Total weight ran into the hundreds of tons . Today vaults are made with thinner, lighter materials that, while still secure, are easier to dismantle than their earlier counterparts.^{[citation needed]}

Bank vaults are custom-designed and are usually one of the first elements considered when planning a new bank building. The vault manufacturer works with the bank to determine specifications like size, shape, and security features. Modern vaults are typically constructed using steel-reinforced modular concrete panels engineered for maximum strength and crush resistance. A 3-inch thick panel of specialized concrete can be up to 10 times stronger than an 18-inch panel of standard concrete.

Bank vaults are typically made with steel-reinforced concrete. This material was not substantially different from that used in construction work. It relies on its immense thickness for strength. An ordinary vault from the middle of the 20th century might have been 18 in (45.72 cm) thick and was quite heavy and difficult to remove or remodel around. Modern bank vaults are now typically made of modular concrete panels using a special proprietary blend of concrete and additives for extreme strength. The concrete has been engineered for maximum crush resistance. A panel of this material, though only 3 in (7.62 cm) thick, may be up to 10 times as strong as an 18 in-thick (45.72-cm) panel of regular formula concreted.

There are at least two public examples of vaults withstanding a nuclear blast. The most famous is the Teikoku Bank in Hiroshima whose two Mosler Safe Company vaults survived the atomic blast with all contents intact. The bank manager wrote a congratulatory note to Mosler. A second is a vault at the Nevada National Security Site (formerly the Nevada Test Site) in which an above ground Mosler vault was one of many structures specifically constructed to be exposed to an atomic blast in Operation Plumb Bob - Project 30.4:Response of Protective Vaults to Blast Loading.

The wall panels are molded first using a special reinforced concrete mix. In addition to the usual cement powder, stone, etc., additional materials such as metal shavings or abrasive materials may be added to resist drilling penetration of the slab. Unlike regular concrete used in construction, the concrete for bank vaults is so thick that it cannot be poured. The consistency of concrete is measured by its "slump". Vault concrete has zero slump. It also sets very quickly, curing in only six to 12 hours, instead of the three to four days needed for most concrete.