A small greenhouse is a wonderful addition to the landscape for any home gardener, but good quality greenhouse kits run into the thousands of dollars. Less expensive, tent-like greenhouses are not sturdy. The good news is that it is perfectly reasonable to design and build your own, high-quality greenhouse for a fraction of the cost of purchasing a good-quality kit, and designing your own means it will be perfect for you.
Finding Affordable Materials
You may build a walk-in greenhouse for the least amount of money by recycling materials in your home and visiting garage sales. There is also the option of "dumpster diving," although many are too squeamish to consider this option. For anything you need that you cannot find, shopping at the lumber yard and the home and garden store will still save you much money over purchasing a ready-made greenhouse. Materials you will likely need include lumber, PVC pipe, greenhouse sheeting and concrete blocks.
A cold frame is simply a raised bed with a greenhouse lid, and is one type of mini-greenhouse. If you already have raised beds in your garden, it is easy to convert them into cold frames. An old shower door laid over a raised bed creates a cold frame for short crops, such as strawberries, salad greens and bush varieties of vegetables. You may also use old windows that fit over the raised bed, but glass can break, so this is less safe.
You may also convert raised garden beds into more versatile mini-greenhouses by constructing an arch over the raised bed. Push a straight PVC pipe into each corner of the raised bed about one foot down. With additional PVC pipes, build arches across the raised bed. Finish with plastic greenhouse sheeting to create a mini-greenhouse. Depending upon the length of your raised bed, you may need to build additional arches along the length of the greenhouse.
Build a walk-in greenhouse on a shoestring budget by employing some of the same techniques as above, but on a larger scale. Level the ground where the greenhouse will sit and dig post holes at each corner. When your posts are set, build a base with 2 by 6-inch boards around the posts and set concrete blocks in the corners for added security. When building a large hoop-house with PVC pipe, include straight pipe supports at the top from hoop to hoop. Take down the plastic sheeting when the season is over if you get snow in your area.