Below grade
When vault designs go into the ground, or below grade, they are typically classified by how deep they are set into the ground. For instance, just as its name suggests, half of a 50-50 vault is installed below grade, while the remaining half is above grade.
Vaults that are constructed below grade still provide the option of adding materials to the exterior portion of the walls to help incorporate the design with the adjacent landscaping. The lower height of below-grade walls can be less imposing, whereas the same size hot tub or swim spa feels and looks smaller and/or more integrated in a 50-50 below grade vault than it would in a 50-50 on-grade vault.
When designing and installing below-grade vaults it is important to design the walls and footings with enough retaining force to hold back the soil. Wall size and design will vary depending on soil conditions as well as the vault’s overall height. For example, if the vault is 0.76 m (2.5 ft) deep and has a 0.76-m exposed wall, the overall engineering and footing design will account for a 1.5-m (5-ft) wall. The wall’s thickness will also have a bearing on the footing design. A licensed contractor will be able to assist homeowners in designing these walls and footings; some hot tub manufacturers offer vault kits, which assist contractors when designing these structures to accommodate a new hot tub installation.
Similar to on-grade vaults, a 50-50 below-grade vault can be designed to leave half of the hot tub visible and not include any walls above grade. This variation involves excavating to the required depth and installing all retaining walls below grade, including the required foundation, drains, etc. For this style of design, it is still important to create an access hatch or area adjacent to the location of the pumps and/or equipment for maintenance repairs. The design (or height) variations are unlimited, thus allowing homeowners to select the style of vault that best suits their landscape and lifestyle.
Flush vaults
Just as the name suggests, a flush-vault design is one where the entire hot tub or swim spa, except for the bar top (the part the cover sits on), is recessed into the ground. This design is extremely popular; however, it requires a little more planning and engineering in some instances.
Drainage and maintenance access still need to be addressed; yet, when built correctly, flush vaults can provide the most integrated esthetic look when added into a landscape design. These vaults allow hot tubs to be installed at the same level as the homeowner’s inground swimming pool. Many flush-style vaults are designed with clearance access on all four sides, which is covered by a removable panel system constructed of a complementing material. For example, porcelain tile access panels installed adjacent to stamped concrete. This creates an attractive change in material on the ground and still allows for easy access to the vault.
In other designs, the surrounding materials can be installed flush with the edge of the vault, adding to the cohesive feel of the design by creating a seamless integration between the vaulted hot tub and the surrounding landscape. Only the equipment side of the hot tub or swim spa is made accessible with a removable panel.
When it comes to external views, these vaults provide a unique aspect for bathers. When inside the hot tub, bathers are at grade level with the surrounding landscaping, which enhances the feeling of privacy as well as the hot tub’s integration into the outdoor design.
Vault upkeep
Not only do vaults need to provide access to the hot tub or swim spa they house, but also to the items that might need to be maintained on the vault itself. This includes being able to remove dirt and debris from the vault and/or verify that it does not contain any standing water. Since most vaults have walls either above or below ground, odd items can become trapped inside. It is also a good idea to provide some form of lighting and/or power outlet as a convenient way to help in the maintenance process.
Incorporate a vault into the next project
While vault installations may not be the answer for every homeowner, if designed/installed correctly, they can become a feature item in the backyard. When constructing a hot tub or swim spa vault, one needs to consider the overall landscape design as well as local construction and building code regulations. Building a secure and safe vault will not only provide homeowners with years of use, but will add value and beauty to their backyard project.
Vic Walker is the product design and marketing manager for Custom Molded Products Inc., a manufacturer of plastic components for the swimming pool, hot tub, and bath industries in Newnan, Ga. He has almost 20 years’ experience as an industrial designer and more than 16 years’ experience in the pool and hot tub industry where he has been awarded more than 15 patents for his contributions. He can be reached via e-mail at vwalker@c-m-p.com.
