Dome Greenhouse Foundation Options

There are a number of foundation options for the Growing Dome. Essentially, the structure is very light; the ground loading is 30-50 lbs/square foot. The purpose of a Growing Dome foundation is basically to secure the Dome to the ground and anchor it. The water tank, being bolted to the foundation wall, also helps in the anchoring process.

Obviously, a complex foundation will significantly add to the overall cost of the Dome, therefore the simpler foundation options are recommended unless there are other important deciding factors. The following factors need to be taken into consideration when deciding on the type of foundation:

BUILDING CODES: Because the Dome is a structure designed and used for agricultural purposes, as well as easy assembling and dissassembling, some building departments waive the requirements for permits and permanent foundations, while others are more stringent. This is obviously an important factor if you choose to consult with them when installing your Dome. In remote areas, some Dome owners have proceeded simply and built their Domes. For more information, see our building department page.

TERMITES: In Southern climates, the presence of termites can make it more necessary to have a concrete foundation with a termite barrier. We also provide a pressure treated lumber bottom plate and fiber-cement siding, both of which are impervious to termites. 

SEVERE WINDS AND/OR SNOW LOADS: In areas of exceptionally heavy snowfall or extreme wind conditions, the Dome structure, although very strong in original design, would benefit from a concrete foundation.

FROST DAMAGE: In areas of severe frost penetration, a Dome on a low cost foundation may experience movement due to the frost / thawing process. Because the Dome is such a rigid structure, this does not create a problem, except occasionally at the doorway. Also important to remember: the foundation has an insulated frost barrier and the soil is heated inside the Dome. Very rarely have we encountered serious problems due to frost damage.

The following are the foundation options we recommend:

• Low cost: The Dome sits on a circular ring of compacted gravel. The blue board undersoil insulation is installed horizontally, as a skirt, touching the bottom of the dome wall, outside the Dome, then covered with gravel. All domes have their own foundation walls as part of the kit.
   
• Intermediate cost: This foundation has concrete sonotube piers at each of the vertices of the foundation (15 or 20) with landscape timbers or compacted gravel in between, and the foundation wall fixed to the piers. This is an excellent foundation for very soft soil conditions.
   
• Higher cost: A plywood formed and poured concrete foundation is one option; an insulated concrete form type foundation is yet another option. Both options makes a strong yet well insulated foundation. Insulated forms consist of an inner and outer layer of polystyrene foam board with connectors. The foundation blocks are cut to the corner angles and fastened together. Re-bar is placed inside the forms. The foundation is then poured with concrete.

Foundation Layout drawings are available to committed buyers. We can also send preliminary drawings to your building department.