Extend Your Growing Season
We love  growing our own vegetables, and most important is that we   control the  quality of our food.  Our soil, the organic and  heirloom   seeds, and chemical-free vegetables we harvest is what we are  about.
After   gathering and canning all the peppers from the plants last  fall, I   noticed at the end of October that buds were  forming on several of the   pepper plants. What a shame that Mr. Frost  would soon take its toll on   these. There was not much I  could do at that point, but I could plan   for next year! Our goal was to extend  our spring and fall growing   season, but do so economically.
Low  tunnel, high tunnel, hoop   house, polytunnel... are similar terms. It   is a kind of greenhouse   that can be made into various sizes, depending upon the space available,   using some form of hoop, a plastic cover and whose source of heat and   light is the sun. It is comprised of a frame, end walls, side walls,  and  a cover.
Much  has been written and is available on the   internet, from those made of  PVC (polyvinyl chloride) to ones using a   steel metal frame. Here are plans for  constructing a 
Simple PVC High Tunnel from Kansas and Missouri authors and this from the 
University of Kentucky on High Tunnels.Our circumstances and considerations included:Location and space (geography):     limiting for us is level ground, coupled with a sunny southern   exposure in   an open area, so options were few and the decision was   made rather quickly. Coincidentally,   it was not far from our potting   shed. The space would allow a maximum   size, 12 feet x 20 feet, and we   would have to bring in a yard or two of   soil in order to make it   slightly more level. 
Height: for this project, the low tunnel was not an option since we wanted to walk upright.
Strength and durability:     occasional winter storms bring high winds from the coast, and with   our   extremely rocky soil, we would anchor all metal stubs in cement before    attaching the steel bows.
Planned usage: we decided upon in-ground plantings with two raised beds on   the west side to include salad greens, spinach, kale, broccoli,   cabbage, cauliflower... On the opposite side would be a raised work   table for seedlings and an area for planting a favorite heirloom tomato,   1 or 2 pepper plants, an eggplant, and anything else we might be able   to squeeze in.
Affordability: a large beautiful greenhouse would be wonderful, but too expensive. Keeping within a budget is always a priority.
Neither   my husband nor I have  any background in construction or engineering,   but we do possess common sense, logic, can read and follow directions   (most of the time),  and are patient (well, that is in degrees also...   ).  We  have seen examples of hoop houses, and with all the information   available from the internet, we knew we could do this. It might not be   perfect, but it would serve our purpose.
We bought the steel   anchoring stubs, the 17 gauge bent steel bows and greenhouse-grade   polyethylene from a  supplier, but everything else was purchased at our   local lumber and  hardware store.
The north end  wall was done in plywood, but the south end was framed and covered in poly. I wanted to be sure we had as much light as possible from the  southern exposure in order to compensate for our cloudy rainy days here in the Pacific Northwest.



Some   adjustments will have to be made as temperatures begin to warm and   stabilize. The fixed lower side  walls will be undone and replaced with    a roll-up device in order to  ventilate and regulate the temperature  of the summer months.
If  you are considering constructing a hoop  house of any kind, be sure to  sit down and discuss your needs, make a  plan, read and research before  you begin.

We gardeners are an  optimistic lot, always looking  forward and preparing for the next  spring, a new season of growth, and  doing what is best for the health  of our families.