Choosing the correct foundation for your greenhouse is critical. Consult with your greenhouse manufacturer, builder, and local planning authority before selecting your foundation type. A greenhouse expert at Solar Innovations, Inc. would be happy to guide you through the process.
While Solar Innovations, Inc. does not provide labor or materials for foundations, we do make recommendations based on the greenhouse’s use and structure type. Please consult your local code official.
Pressure-treated lumber can be bolted together to form a foundation for greenhouses under 200 square feet, commonly referred to as “hobby-sized.” Greenhouses less than 6’ x 8’ can be constructed on a foundation of one tier of lumber. A 10’ x 12’ structure will require two tiers of lumber to create a solid foundation. Two-foot sections of rebar should be inserted into the ground and fastened to the lumber base for added strength.
A stronger foundation is necessary with a greenhouse larger than 200 square feet. Options include: a concrete slab, a continuous concrete footing, or a concrete block footing. Footings should extend below the frost line to prevent frost heave. A concrete block footing should extend a minimum of 6” above grade to form a knee wall. Tying a greenhouse to a foundation or footing can be achieved by embedding anchor bolts into concrete. It is recommended that a water proof compound be applied as a moisture barrier and surround the foundation with insulation panels.
Knee walls (sometimes referred to as “base” or “pony” walls) are commonly featured in the construction of greenhouses. Applying a stone or brick veneer directly to a concrete knee wall is a cost-efficient way to achieve a classic aesthetic. Solar Innovations, Inc. recommends insulating the knee wall to optimize heating and cooling. Knee walls are typically between 30” and 36” tall. Storage pieces, furnishings, and garden tools can be hidden from external view when walls are formed.
Selecting flooring is a very important decision in the design of your greenhouse. The floor needs to be comfortable for the gardener, allow drainage, and be sterile. All floor systems need proper drainage and slope to remove excess water. One option is to install a French drain into the foundation as it is poured. Solar Innovations, Inc. does not supply materials or labor for flooring, but we do make suggestions based on the greenhouse’s primary function.
Concrete is an economical selection for a greenhouse. Simply use your foundation as the floor. Concrete can increase thermal mass storage and does not harbor mold or disease; however, it will require regular cleaning due to soil build up.
Using a paver floor is another economical choice. Pavers are typically used on smaller scale greenhouses that do not require concrete foundations. Pavers are placed directly upon the soil in a pattern which adds character to the structure.
Tile is durable and easy to clean. There are many color and pattern options to achieve a specific design. Use slip resistant or textured tile to help prevent falls.
Gravel is the most economical choice and easy to install. It reduces the spread of mud and dust. However, gravel may need to be replaced more frequently than other options. Depending on the gravel’s density, weeds may sprout.