This May we finished constructing our 30'x48' hoop house. Our goal is to use it to get heat loving crops like tomatoes, cucumbers, okra, melons, etc. started earlier, and to extend our season by growing hardy greens like spinach, kale, and arugula later through the winter. There were a lot of decisions to make concerning greenhouse construction: manufacturer, end wall construction, orientation, location, and many more. We spoke with friends and fellow farmers who have greenhouses, and we also found it helpful to search the web and see pictures of how others have done things. Here's how we chose to build ours.
We went with the Ledgewood frame, with a few Rimol accessories (such as wiggle wirelock to secure poly to the frame). In order to maximize solar energy in the winter, we went with an east/west orientation with a double layer of poly over the house. We left the eastern endwall in poly, but for added ruggedness we decided to build a solid western facing endwall (our predominant winds come from the northwest). We used some salvaged tongue and groove cedar we had on hand for the endwall and doors, and it came out looking great. With the ground posts sunken two feet into our heavy clay soil and with a solid endwall, we're confident this house isn't going anywhere.
Once the house was built, our next decision was to figure out how we wanted to grow inside the thing. Our first decision was to install a french drain system inside the house to keep our growing area dry. Again, with clay soil the key is giving the water somewhere to go. Breaking sod in the spring with our soil is no easy task, and all through construction there was pooling water throughout the house. But once the poly was up, and I started giving the water a place to go, drying finally started. I dug 2' wide ditches that were about 2' deep inside each baseboard, and ran the ditch past the western endwall into the existing drainage ditch we have for our garden. With clay soil, hand digging is never easy. Then, I layered a few inches of crushed stone at the base of the ditch, followed by perforated pipe, and topped it off with more stone. Our first rain storm quickly followed the completion of the ditching, and much to our delight the water was running out of the drain pipe and our growing area stayed dry.
Now it was onto the beds themselves. Because we're used to working with unforgiving clay soil, we decided to build permanent raised beds. Its more work up front, but it relieves us of the tiresome task of trying to till a hardpan each growing cycle. Not to mention we felt like it would maximize our small greenhouse's growing capacity. We used 1" wide rough hemlock for the frames of the beds, reinforced from the exterior with 24" masonry stakes. To fill our beds we mixed some of our own compost, along with some additional purchased compost, with the soil raked from the walkways. We gained close to 12" of growing depth above the walkways. We won't be able to get equipment like the tractor or tiller into the greenhouse, but we shouldn't need to. Only periodic compost amendments with the wheelbarrow will be all we should need.
Of course, the whole greenhouse construction plan was pushed back by several weeks due to uncooperative weather. We were a couple weeks later than we would have hoped getting our tomatoes into the raised beds so they were a bit leggy. We used 1" conduit the lengths of the beds to attach trellis lines to, and it wasn't long before the tomatoes began to take off. Out tomatoes, okra, eggplants, and peppers loved growing in the house so much we're going to build another one!