Basic vault concepts
Vaults are functional enclosures that should be constructed by a licensed contractor as there are many considerations that need to be addressed in order to design/build them correctly. A basic, but important, consideration is soil. For example, various soil types will play a factor in the design and size of the footing required for a vault wall, whether it is being built above or below grade. Further, the type of reinforcement bar required in the construction of the wall and footing will vary according to the wall’s thickness and what building and finishing materials are being used (e.g. stone veneer). Contractors will have experience working with different soils as well as local building codes; therefore, they should have a good idea of what footing design is required for any given design.

Another important consideration is drainage, especially for vaults designed below grade. These vaults require the installation of a drainage system that can not only handle environmental water (e.g. rain and melting snow), but also splash out from the hot tub or swim spa. This is a crucial design element in swim spa vaults as more water is pushed out of these spas during swimming and exercise. Ideally, vault drain systems should be tied into an existing landscaping drain. For projects using a gravel base, a ‘French drain’ (i.e. weeping tile) system can be employed, and depending on soil conditions, these drains are effective at handling excess water. Another option is to install a pump system that ties into exiting drains or evacuates water from the vault to another location. These pump systems use floats, which activate automatically once the water has reached a certain level. These pumps will keep the vault dry in rainstorms and during heavy usage.
Adequate access is also important to the design. The equipment in most hot tubs and swim spas are typically located in one area; therefore, it is a good idea to make this area accessible for routine maintenance and/or repair. Further, as hot tubs and swim spas need to be drained and filled frequently, drain outlets should also be easy to get to. In some cases, contractors can install a simple ball valve that can be easily reached when the hot tub is inside a vault. Water is then emptied right into the vault’s drain system, making this maintenance routine easier to perform. If the exterior cabinet of the hot tub or swim spa will also need maintenance, this should be considered in the design as well.
Finally, another form of access that should be well thought out is ingress and egress. Obviously, a set of integrated steps make above-grade vaults safer to use; however, they can become part of the integrated design by simply incorporating materials, which have been used throughout the backyard landscape, e.g. matching other steps or walls in the yard.
Vault styles can vary

Hot tub and swim spa installations are limitless in style and design. And, thanks to vaults, depending on the homeowner’s preferences and the design theme of their backyard, they can also be installed in a variety of configurations. Many vaults are identified by how much of the product is either hidden or revealed. While these are almost infinite, the following will discuss some of the more typical styles and/or configurations being used today.
Above grade
Above-grade (i.e. on-grade) vaults are one of the most popular styles as they do not require a large excavation. They do still require a footing; however, so some digging is necessary.

These full-vault structures are designed and built on grade to cover all sides of the hot tub. Its walls can comprise poured concrete, brick, or concrete masonry unit (CMU) blocks, and then finished in any one of a variety of hardscaping materials.

A full-height, on-grade vault is one which fully encloses the hot tub or swim spa and extends to the top of the unit. These vaults also typically include a maintenance access hatch in the front where the equipment is located. Often times, steps are built into the sides of the vault walls not only to promote ingress and egress, but to also create visual interest.

A full-height, three-wall vault is another popular option as this design creates more of an alcove by leaving one side of the hot tub exposed. These vaults can be built in a variety of heights depending on what the homeowner wants. For example, a vault can be built to cover only half of the hot tub or swim spa (i.e. a 50-50 installation). In some cases, this is more cost effective (since there is less to build); however, it still helps to blend the hot tub or swim spa into the landscape.
On-grade vaults can easily become the focal point of a backyard as the sides of the vault act as a canvas for the homeowner to decorate as they desire.