4 We might as well get this out of the way. Here is the most important tip I can give you about greenhouse foundations: Your greenhouse foundation MUST be level and square to properly anchor the greenhouse. The greenhouse is manufactured true and square and must be installed this way. What if it is not level, you might be asking yourself? If your greenhouse foundation is not level, you might experience: *  the frame and panels will not align and you will think you have to cut into something and you don’t, it’s the foundation *  the framing for the door will be very tough to install and then the greenhouse door will not hang properly Okay moving along to the types of foundations… The most common foundations for hobby greenhouses are wood or concrete. Wood is the most popular choice because it is easy to work with and easy on the pocketbook. The other benefit is that wood can be easily adjusted down the line if you decide to move or extend your greenhouse. p !