The triple vault was the first vaulted structure built at CalEarth in the early 1990s. The walls, built 5-feet high, are all individual sandbags (unstabilized) and the vault slabs were poured in small 3-4 feet increments. The 14-foot wide vaults were made in three sections (to the size of the scaffolding, which was moved again and again) and include thick buttressing and "reptiling" (small earthen balls) outside.

This building was tested in 1995 and passed the full set of seismic tests required in the state of California. This design was later evolved into the Earth One design, which uses the same stacked vault layout to create flow between spaces without the need for hallways. The Triple Vault also features the first wind scoop built a CalEarth, a passive cooling system that brings in air and circulates it throughout the space without the need for an air conditioner. The Triple Vault is submerged 3 feet below grade, a design that is especially useful to combat the extreme temperatures in the Mojave desert. The hole dug to submerge the vault supplied the bag-filling and roof material.