Types of Footing for an Outdoor Greenhouse

Updated March 23, 2017

When adding a greenhouse to your garden or landscape, you will need to make sure you have a level area to install or construct your structure. Footings, or foundations, for your greenhouse should share a few simple characteristics: the foundation should be anchored to the ground, it should be well-drained and it should be relatively free from gaps where weeds or grasses might enter.


A wood foundation provides an inexpensive foundation and is relatively simple to build. The design consists of a wood foundation with an aluminium frame. Choose woods that resist decay and mould, such as cedar or redwood. If you're using a pressure-treated wood, be sure to include a barrier material between the wood and aluminium greenhouse frame, as the chemicals in pressure-treated wood are corrosive to aluminium. A wood footing will also require a ground cover or weed barrier, which you can purchase at your local home and garden store. Avoid using tarp, as it is not designed to allow for drainage.

Concrete Slab

A concrete slab foundation sits atop the ground, generally over a moisture barrier and layer of compacted gravel. The slab should be longer and wider than the greenhouse itself by at least 1 inch on all sides. The depth of the slab, or thickness, should be 3 inches for a greenhouse. To ensure proper drainage, a concrete slab will need a centre drain system with piping that leads well outside the footing of the structure. A concrete slab is poured directly into a wood frame and allowed to set. Once the concrete is dry, the wood framing is removed and the structure is built on top of the slab.

Concrete Wall

A concrete wall foundation has a footing that sits below the frost line, thus creating a stronger and more substantial foundation than the wood or slab types. In most cases, this type of footing will require a building permit, as you will need to dig a trench and place forms in the ground. Once the trenches are completed, concrete is poured in to form a below-grade foundation. The structure is then attached with bolts. This is a more permanent option and works well for larger greenhouses, particularly those with all glass walls and ceilings.

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About the Author

Augustus Clipper began writing professionally online in 2009. His areas of expertise include home gardening, landscape architecture and interior design. He received his Bachelor of Arts from the University of California and his Master of Arts in English literature from New York University.