There are a few greenhouse foundation options for Growing Spaces® Growing Dome greenhouses. Essentially, the structure is very light; the ground loading is 30-50 lbs/square foot. The purpose of creating a greenhouse foundation is basically to secure the solar greenhouse to the ground and anchor it. The water tank of the Growing Dome is bolted to the foundation wall, which also helps in the anchoring process.
Obviously, a complex greenhouse foundation will significantly add to the overall cost of your project, therefore the simpler greenhouse foundation options are recommended unless there are other important deciding factors to be considered. The following factors need to be taken into consideration when deciding on the type of greenhouse foundation:
Greenhouse building codes: Because Growing Dome greenhouses are structures designed and used for agricultural purposes, as well as for easy assembling and disassembling, some building departments waive the requirements for permits and permanent foundations for Growing Dome greenhouses, while others are more stringent. This is obviously an important factor if choosing to consult with your building department when installing any greenhouse. In remote areas, some owners of green houses have simply proceeded and built their Growing Dome Kits. For more information, see our building department page.
Termites: When considering a greenhouse foundation in Southern climates, the presence of termites can make it necessary to have a concrete foundation with a termite barrier. We also provide a pressure treated lumber bottom plate and Pro-Wood siding for our Growing Dome greenhouses, both of which are impervious to termites.
Severe winds and/or snow loads: In areas of exceptionally heavy snowfall or extreme wind conditions, the structure of our solar greenhouses, although very strong in original design, would benefit from a concrete greenhouse foundation.
Greenhouse frost damage: In areas of severe frost penetration, Growing Domes installed on a low cost greenhouse foundation may experience movement due to the frost / thawing process. Because our green house kits are such rigid structures, this does not normally create a problem. Also important to remember for Growing Dome greenhouses: the foundation has an insulated frost barrier and the soil is heated inside the green house. Very rarely with our geodesic green house kits have we encountered serious problems due to frost damage.
The following are the greenhouse foundation options we recommend:
- Low cost greenhouse foundation: In this option, the Growing Dome greenhouse sits on a circular ring of compacted gravel. The blue board undersoil insulation is installed horizontally on the outside of the Growing Dome as a skirt that goes against the bottom of the greenhouse wall, and then it is covered with gravel. All Growing Spaces solar greenhouses have their own foundation wall as part of the kit.
- Intermediate cost greenhouse foundation: This Growing Dome greenhouse 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. For our Growing Dome greenhouses, this is an excellent foundation for very soft soil conditions.
- Higher cost greenhouse foundation: A formed and poured concrete greenhouse foundation is one option; an insulated concrete form type greenhouse foundation is yet another option. Both options for our Growing Dome greenhouses make a strong yet well insulated foundation. Insulated forms consist of an inner and outer layer of polystyrene foam board with connectors. The greenhouse foundation blocks are cut to the corner angles and fastened together. Re-bar is placed inside the greenhouse foundation forms for added stability. The foundation for the Growing Dome green house kit is then poured with concrete.
Greenhouse Foundation Layout drawings are available to committed buyers of Growing Spaces Growing Domes. We can also send you preliminary drawings for you to take to your building department.