• Measure the width of the widest part of the crop to be protected and add roughly four inches to each side in order to keep the crop from coming into contact with the film later. For newly planted crops or seedlings in early spring, you will need to estimate how large the plants will be in two or three weeks or the estimated amount of time it will take for the weather to turn warm.

• Measure the tallest plants to be saved or grown and as above, add roughly four inches to this height.
   

• Now take these measurements and transfer them to 3/4" chip board (like the kind used for sub-flooring in home construction) or plywood. Provided your widest measurement is not over four feet wide and four feet tall, you will be able to get two pieces out of a 4 x 8 foot sheet. These will become the rigid ends and partitions for your cloche and we'll discus these more in a moment. Now along one of the straight edges of the chip board, measure out and mark the width of your cloche and make a mark halfway between these two points. From this center point, measure up a distance equal to the height of your crop and make another mark for the apex (top) of the cloche. Now either free hand or using a string, nail and pencil for a make-shift compass, draw a "half-circle" arc. You now have the outline of one end. (see figure 1)

• Using an electric Jigsaw, cut out this end following the line you just drew.
   

• Use this cut out end as a template to draw the outline for the other end and any inner partitions and cut these out the same way as the first.
   

• Now measure from one corner of the end partition across the top to the opposite corner of the board. This will give you the length of the hoop ribs you will cut later. (see figure 2)

• In the center of the top of the arch and 3/8" from the edge of the arch, drill a 3/4" hole through the partition for the center beam to be installed later. For ease of drilling the holes in the same locations on all of the pieces, clamp the partitions together and drill all partitions at one time. You should end up with a hole that is slightly breaking through the top edge of the boards. (see figure 2)
   

• Measure down approximately 3" from the top of the arch plus half the diameter of the vent hole you plan to make and in the center of the board width-wise (this will give you the center of the hole), cut out a 6" to 8" diameter hole for ventilation. The larger your cloche is, the larger this hole should be and for a 48 inch x 48 inch cloche I would probably go as large as 10 to 12 inches diameter for the ventilation. For ease of cutting all holes in the same place, clamp all of the partitions together and saw all holes at one time. Cover the holes of the two end pieces with hinged, flap-type covers or doors later (end partitions only). (see figure 2)

• Cut out two "doors" (vent covers) to cover the two end ventilation holes. For this you will need a fairly thin material (whatever is handy) such as 1/4" plywood, pressed hardboard from an old drawer bottom, etc. Cut these pieces two inches wider in all directions than your vent holes (e.g. - a 6" hole will need two pieces 10" square, an 8" hole will need two pieces 12" square, etc.). (see figure 3)
   
• Now take all of your wood pieces and paint them thoroughly with a good house paint. For new wood, use a paint primer first. That way the paint will adhere better and the pieces will last longer. I generally like to use two or three coats of paint, allowing each coat to dry between coats.
   
• Measure the total length of row to be covered (in inches) and divide that number by 12" to 18" (spacing between hoops spaced evenly) to arrive at the total number of hoops needed and subtract two (for the two ends).
   
• Now using 1/2" PVC pipe or 1/2" PVC electrical conduit (both available at a hardware store or home center), cut the correct number of hoops to length. A PVC pipe cutter works very well (also available where you get your pipe) or a simple hack saw or hand saw will also do the job nicely. Note that PVC pipe does not bend a tighter radius than about 2 feet without being heated or it will bend and kink the pipe, which 24" should the narrowest cloche of this type you will probably make or that I suggest.

• Cut a piece of galvanized, metal electrical conduit (called EMT or Electrical Metallic Tubing in the trade) to the length of your row (also available where you get your pipe) with a hacksaw or metal tubing cutter. Conduit comes in 10 foot lengths, so if your row is longer than 10 feet, you will need additional pieces of conduit and use conduit couplers (set-screw type if possible, also available where you get your conduit) to connect the pieces together when assembling the cloche. 1/2" galvanized water pipe will work even better, but it is a little harder to work with, it's heavier, more expensive and you will need to adjust the size of the holes you drill in the partitions. However, it comes in 20 foot lengths (actually, it is normally 21 feet if bought from a plumbing supply house), is much stronger and will require fewer pieces if your row is long. Drill a 1/4" hole through each end 3/8" back from each end for a screw to attach each end to end board. Also drill a hole in the location of each inner partition you plan to install. Do not plan on spanning more than 10 feet unsupported with this beam or the beam will sag and possibly collapse in adverse weather.
   
• When your paint is thoroughly dry, take the two end caps (vent flaps) and attach two small hinges (galvanized or other rust resistant material such as brass) to one edge of the flap and then attach these to the two boards that will be the two ends of your cloche. Make sure that the flaps are centered over the holes and swing freely. (see figure 3)

• Now slide the conduit through the 3/4" holes in the tops of the partitions and making sure that each end (and any inner partitions) is setting flat on the ground, secure the conduit to the partitions with a wood screw approximately 1 1/2" long to form the main sub-assembly. It helps to have a second person for this if possible. (see figure 3)
   
• Set the sub-assembly in place over your crop or row and center it as evenly as possible and drive one or two stakes into the ground beside each partition and screw the partitions to the stakes. Make your stakes approximately 24" long and drive 12" of the stakes in the ground. I prefer to use 1x2 stakes that I cut out of pressure treated lumber for longer life. (see figure 4)
   
• Now stretch a line along each side of the sub-assembly to guide the placement of stakes you will drive in the ground to hold your plastic ribs. (see figure 4)

• Now cut stakes (hoop pins) 18" long out of 1/2" concrete reinforcing bar (most hardware stores and home centers will cut the bar for you at little or no cost if you are buying it from them). The number you will need will be two per hoop you are installing.
   
• Following the lines you just stretched on both sides of your sub-assembly, drive the stakes 12" into the ground at the spacing you previously figured. You will be left with 6" of stake left above ground, over which you will slide one end of the hoops. (see figure 4)
   
• Now take the hoops you have previously cut and slide one end over one of the stakes you just installed. Gently bend the hoop over the sub frame and slide the other end over the corresponding stake on the opposite side. Adjust the hoops up or down until they just touch the conduit center beam of the sub-assembly. Continue this procedure until all of the hoops are installed.

• Using twine or wire, secure the hoops to the center beam of the sub-assembly.
   
• Apply hook and loop tape (Velcro - available at hardware stores and home centers in a tape form) to each side of the two ends. (see figure 5) The side attached to the wood will probably need to be stapled (using copper or other rust resistant staples) to hold the tape securely. Leave a space of about 12" along top to permanently attach the film later, however there is no reason why you can not apply hook and loop tape over the entire surface. Do not remove the tape backing on the side that will be next to the plastic at this time.
   
• Unroll the film you are going to use as the covering and cut it approximately 6" to 8" longer than the length of the cloche (divide this length equally on both ends). When you choose the width of your film, make sure that it will be wide enough to go completely across the cloche and have approximately 6" to 10" on the ground on each side as excess. You will use this excess as a place to weigh down the sides when the film is installed.

• With the help of a friend, drape the film across the cloche frame and center it in all directions.
   
• Stretch the film straight and somewhat tight across the top. Where the plastic crosses the top of each partition, staple the film to the partitions (reinforce the plastic with cardboard or heavy duty tape before stapling).
   
• Now remove the tape backing from the hook and loop tape on each end and press the film onto the tape to secure the film to the tape. Use care here to keep the film straight before you stick it down or you may tear the film trying to reposition it. Make sure to press the film down firmly on the tape for good adhesion.
   
• Now straighten the excess along the ground and weigh it down with bricks or other suitable weighs about every 12" to secure it. Theses edges can be attached to lengths of pipe to allow the sides to be rolled up like blinds if you like, but they should still be weighted down.
   
• Make suitable props of your choice to prop the vents open on each end during warm weather (be as creative or as simple as you like here). Check the cloche often during sunny or warm weather and lift the side (away from the wind) if needed to keep the temperature from becoming excessive. Make sure to close the cloche back up tight each evening to retain heat.
   
• For convenience and increased usefulness:
  • Purchase an inexpensive dial-type thermometer and carefully seal the face edges of the dial face with silicone and insert it through the top on the film in the center of the cloche. This will allow you to easily monitor the internal temperature.
  • Cover the soil for approximately 3 feet on each side of the row with black plastic to absorb heat (do this before you install the cloche).
  • Paint plastic gallon milk jugs with flat black paint. Fill with water and place every 1 to 3 feet inside cloche to absorb heat and re-radiate it at night.
  • For greater strength and durability, place a partition every 6 to 10 feet of length. Flap covers should be left off of interior partitions for better air circulation.

With these measures, it may be possible to raise many cold weather crops all winter long in many areas that could not do so otherwise. Yes, you can build a much less involved and less expensive cloche than this one, but I have found that these lighter units can be pretty flimsy in a heavy snow, wind or rain and will occasionally collapse or sail away in a high wind unless you're very careful about securing it.

If you have access to many old windows of the same size, these can quite easily be transformed into a build-where-needed A-frame greenhouse/cloche of sorts. But access to the plants and ventilation will be much more difficult.

Good luck and good gardening!