Should You Build a Greenhouse Foundation?

Large greenhouse in a field of snow
  • 4-40 hours
  • Intermediate
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Gardeners have plenty to consider when thinking about building a greenhouse foundation. Greenhouse construction is a primary consideration while selecting the style of greenhouse frame. It is necessary to take a number of different things into consideration before making a final decision.

Is a Foundation Necessary?

The simple answer is no. A greenhouse foundation is not necessary. Many professionally built greenhouses of different sizes do not have any foundations at all. A greenhouse can be readily installed as a free-standing unit without having a detrimental effect on a garden or the plants that are growing within the garden.

However, while a foundation is not a necessity, it may be desirable in some circumstances--particularly in earthquake zones or where permanency is required.


cement foundation

A greenhouse foundation can be made from an assortment of materials. For instance, many small greenhouses have simple wooden 4x4 foundations. Other greenhouse foundations are made from poured cement. Concrete wall foundations may be another option. While it is possible to build a wooden foundation by yourself, it may be necessary to hire a professional builder to install a concrete foundation.

Building Codes

It is important to check with your local officials before installing the foundation for a greenhouse. You may need to get a permit or there may be a zoning law that states foundations cannot be used. Alternatively, there may be a rule that states that only a certain type of foundation can be used.

If it is not possible to put down a foundation, there is an alternative. Consider using landscaping fabric or another type of walkway in the greenhouse. Rocks or bricks could be used. Bricks will require digging so their tops sit flush with the ground.

Another problem that some gardeners might face is that zoning laws may require professional installation of the greenhouse foundation.

Building Costs

person making calculations

An affordable choice for a wood foundation is 4x4 pieces of lumber. Cement options are invariably more expensive. If hiring a professional builder becomes necessary, labor costs can drive foundation prices up significantly. It may be necessary to set a budget for the entire greenhouse project. Determine the budget before you begin and stick to it.

Other Considerations

When using cement as a foundation for a greenhouse, it will become necessary to level the ground on the site after removing sod and plants. If the area where the foundation will be laid is in a cold climate, the foundation and frame should be put deeper into the ground. Warmer climates only require a few inches of foundation depth due to the depth of the frost line.

It may also be necessary to insulate the foundation. If you use foam to insulate, install it to the depth of the frost line.

The frame will need to be secured to the foundation so consider how this will be accomplished in relation to the type of materials used for the foundation.