Deciding On Your DIY Greenhouse Foundation
If you have questions on how to build a greenhouse, one of the first things you’ll need to do once you decide to install a greenhouse in your yard is choose a suitable foundation. Even though most modern greenhouse plans offer suggestions on which foundation is appropriate, you have options. The foundation is critical to the stability of the greenhouse and will be responsible for supporting the structure and anchoring it in place. You have several options with the materials you use for your greenhouse foundation and the one you finally choose is dependent on the size of your greenhouse, its location and your budget.
A Wide Range of Options for Your Greenhouse Plans
There are three main types of greenhouse foundations that are commonly used today and are either made from treated wood, a beam and pier construction or a concrete wall foundation. Each of these will work for most greenhouses but there are advantages to each type that can help you make your decision. The key thing to remember with any DIY greenhouse is that you’ll need to prepare the area well before starting your foundation and be sure to select an area with good drainage to avoid flooding and other problems over time with your greenhouse.
Wood Is a Very Common Choice
The simplest and most common type of foundation in use today is made from pressure treated wood. This is a great option for a smaller DIY greenhouse and is also the least expensive choice for most homes. With this type of foundation, the wood is placed directly on the ground and needs to be treated to help prevent it from suffering damage over time from wood rot. The wood also needs to be strong enough to support the weight of the greenhouse and provide a way to anchor the structure to the ground. Building this type of foundation is simply a matter of bolting together several large 4X4 posts into a square the same size as your greenhouse. The ground in the area of the greenhouse needs to be cleared of grass and plants and then leveled. These boards are then laid on the ground and anchored there with rebar that is attached to the frame and driven below the frost line. The preparation for a wood foundation is slightly easier than other choices and won’t involve the more extensive excavation of using concrete.
Beam and Post Is an Easy Alternative
A beam and post foundation is the next easiest choice for many greenhouse plans and is the only one that doesn’t rest the floor of the greenhouse directly on the ground. With this type of foundation you will be installing several concrete or wooden posts into the ground around the perimeter and possibly down the center of the greenhouse that will support its weight. Once these posts have been sunk into the ground, there will be beams attached to the top of them that form the frame for the floor. The greenhouse will be anchored to the edges of this structure to keep it in place. If you use this type of DIY greenhouse foundation in warmer climates, you can use a shallower post to support the structure since the chance of freezing is small. In colder climates the post will need to rest on a more substantial base that is located below the freeze line to prevent lifting of the greenhouse from the shifting ground beneath.
Concrete Will Stand the Test of Time
A concrete wall foundation is used for larger and more permanent greenhouse locations and will provide a very stable and secure base. Even though this type of foundation involves a little more work and planning, it will ensure your finished greenhouse will have the support it needs for decades. This type of foundation is also recommended for colder climates as it helps eliminate the effects of ground freeze on the greenhouse structure. Other less substantial foundations will tend to move in colder climates and may cause damage to the glass walls of greenhouses that are twisted by this movement.
Installing this type of foundation involves trenching around the perimeter of the DIY greenhouse to a depth below the frost line. Once this trench is completed, the bottom is covered with 2” of crushed stone and a wall form is installed that is then filled with concrete. For larger walls, rebar is also used to help prevent cracking of the concrete. Once the wall is finished, a treated wooden sill is attached to the top of the wall and the greenhouse is anchored to this sill.
Whichever type of DIY greenhouse foundation you decide to build be sure to follow any local building codes in your area. These codes can vary slightly and will be specific to your specific weather and ground conditions to make sure whatever structure you build is safe. You also need to remember that since the greenhouse is supported by this foundation, it’s important that you take your time to set this foundation properly to avoid problems later. You want whatever foundation you finally decide to build to last the life of your greenhouse.