Choosing a Foundation for your
DIY Greenhouse

One of the first steps after deciding you want to build a greenhouse or conservatory is choosing a foundation/flooring material. Keep in mind that most of the low cost DIY greenhouse kits do not include flooring. Each type of foundation has its own price tag and take different amounts of work and time to build. Whatever type of flooring you decide to install, with a little knowledge, you should be able to do it yourself!

Depending on the size of the greenhouse/conservatory you are going to build, you may need a foundation or not. Small hobby greenhouses usually don't require a foundation at all because they are easy to heat. Larger greenhouses and conservatories need a foundation to absorb heat during the day and use it to keep the greenhouse warm at night.

If you decide your greenhouse needs a foundation, there are a few things that it should provide:

1. Drainage - There must be a way for water to drain out of the greenhouse. Should you spill water or use a misting system, proper water drainage is key. If water doesn't drain, it will collect on the floor and in flower pots. Stagnant water promotes many types of algae and insect growth. The high humidity and moist growing atmosphere provide a perfect breeding area for several types of gnats, flies and worms. They can breed in virtually any accumulation of standing water that remains in place for several days. I can't stress enough the importance of proper water drainage in your greenhouse.
2. Anchorage - To prevent your DIY greenhouse from blowing away in the wind, anchoring it to the ground is important. Most of the DIY greenhouse kits are built using light materials such as PVC and polycarbonate sheets. Because of the greenhouse's low weight, wind gusts can move or turn over a greenhouse.
3. Weed Barrier - Weeds will do their best to creep into your greenhouse so it's important to take appropriate measures to prevent it from happening. You may not realize the importance of controlling weeds in and around your greenhouse. As well as being an eyesore, weeds can harbor insects, viruses, bacteria which can be transferred to your greenhouse plants. It's important to lay down weed block fabrics or plastic sheeting before your foundation. I've heard to never use mulch or straw because it can become a nest for bugs and pests.
4. Frost Protection - Most small to medium size DIY greenhouses do not need cement footers that extend below the frostline. However, foundations for glass covered greenhouses 12" x 16" or larger should. This does not apply to the typical DIY greenhouse.

There are many types of greenhouse/conservatory foundations to choose from. The size, budget, and look of your greenhouse will help you decide which flooring to install in your DIY greenhouse. Here are a few types of greenhouse foundation/flooring:

• Dirt - A dirt floor is the most inexpensive flooring option because in the majority greenhouse installations, the dirt is already there. The advantage of having a dirt floor is that the water will absorb easily and you can benefit from the natural heat as well. The disadvantage of have a dirt foundation is it can be a mess. Too much water mixes with the dirt and you can begin making mud pies! Maybe you could use a little gravel to help with the messy dirt & mud.
• Treated Wood - A dirt floor is also an inexpensive foundation option because you can usually pick it up pretty cheaply at your local hardware store. The important thing to know about laying wood as your greenhouse foundation is making sure it is pretreated and that you continue to treat the wood. If you fail to maintain your wood flooring, it will not hold up to the moisture and water used in your greenhouse gardening. Be sure to ask about the different grades of treated wood as some can corrupt common steel, aluminum, and low-grade galvanized hardware.
• Concrete - A concrete floor is common among large greenhouses and ideal for areas with hard winter freezes. When considering to use concrete as the foundation/flooring in a large greenhouse, you may need to contact a professional to lay the concrete with water drains. Concrete floors also a great for storing heat and easy to clean and maintain. The downside of having a concrete foundation is that it is permanent.
• Brick/Stone - A brick or stone floor is also a common foundation choice. Adding adequate spacing between the bricks/stones will allow water to drain and easily absorb into the ground. Bricks and stones also hold heat very well and are a nice choice if cold weather is going to be an issue for your greenhouse.

After you have decided on the proper greenhouse foundation/flooring, it's important to take your time and install it properly. Be sure to remove any sod, grass, weeds, etc... as your first step. Then, always, always, always start with a packed and leveled dirt floor. By building your foundation as square and solid as possible, your greenhouse should bring years of enjoyment to you.

By Tiffany McCann