How the standby generator is mounted is an important aspect of the installation process. The generator must be protected from any moisture that may come up from the ground. It also must be provided with a solid and level surface. In addition, installers of standby generators must consider local building codes in their plans. Installers are expected to comply with the National Electrical Code, which is implemented by the local authority that has jurisdiction over the installation of the generator. It is this group that ultimately has to approve the installation.

Therefore, there are a variety of base designs on which a generator can rest. They include:

• Pre-Cast Concrete
• Concrete Pad Made On Site
• Custom Pedestal
• Compacted Soil Or Gravel Bed

All but one design uses concrete in some form. The only design that doesn’t is the compacted soil or gravel bed.

Pre-Cast Concrete Pad

Generally, the generator’s manufacturer, the company doing the installation, or a local company that specializes in creating concrete manufactures the base off-site of where the generator is being installed. Simply put, the concrete is mixed and then poured into a form where it hardens. Curing commonly takes up to a week to assure that the base or pad is of full strength. If the generator manufacturer is supplying the pad, then it is purchased along with the generator and shipped.

Prepping for an installation of a generator includes leveling the soil. This may include an installer removing a rectangular patch of grass and soil and the addition of sand and gravel that is then compacted. The pre-cast concrete pad is then placed over the prepared surface. The pad is commonly 3-inches to 4-inches thick depending on the weight of the generator. It is up to the installer to ensure that the pad is stable before he can mount the generator on it.

Advantages of pre-cast concrete include its lower cost, its thinnest, longer span lengths and low maintenance.

Concrete Pad Made On Site

There are conditions that call for the concrete foundation to be a part of the soil. Under certain circumstances this offers a more stable surface that is less likely to sink or move. In addition, local building codes may require this type of pad over other pad designs.

In this case, the installer is required to remove soil and then compact the area. Sand and gravel may be added into the dug out space that is compacted to offer proper drainage and a stable surface for the concrete. Wood is used to create sides that offer a frame. The installer mixes the concrete, pours it into the space, and levels and textures it. In addition, some installers have been known to round the edges.

It takes several days for the concrete to harden properly. Only when the base is fully cured will the generator be placed on top.

Although this form of pad is more expensive than other alternatives and takes more time to construct, it does offer better stability and its depth easily adjusts to the weight of the generator.

Custom Pedestal

In some cases, it may turn out that the best location for a standby generator is subject to flooding. This is when the custom pedestal base design is used. The pedestal is raised and therefore protects the generator from the water. There is one requirement that must be satisfied in this particular design. The pedestal cannot be too high because it could cause a problem for technicians in maintaining the generator.

The construction of this base includes a concrete foundation, which secures the pedestal, and wood forms that create its sides. The interior of the pedestal is hollow, which can be filled with sand or gravel after the wood forms are removed.

Although a custom pedestal may be necessary in areas that are susceptible to flooding, keep in mind that it is more expensive than both the pre-cast or made-on-site alternatives.

Compacted Soil Or Gravel Bed

This base design meets the minimum requirements for most air-cooled, home standby generators if the soil conditions are right. However, it should be noted that overtime the soil might move leaving the generator tilted. This base design is not suggested for areas that experience heavy rains or flooding. Moreover, the installation of this design must avoid grass that could grow right up to the generator. This can cause problems with airflow or cause the collection of debris.

Construction of this type of base include the removal of grass and 3-inches of topsoil. A layer of compacted gravel may be added to stabilize the site and offer good drainage. A composite pad is laid over and the generator sits on the pad.