Build Your Own Polyfilm Hoop House Greenhouse
There are a lot of reasons to build your own polyfilm greenhouse rather than buying a kit. You may have a special feature or size that you cannot find in a kit. Maybe you have some materials you can recycle. Or, you may just enjoy letting your creative juices flow and making your greenhouse from your own hands with your own design. There are a few basic steps you should follow making decisions regarding your greenhouse whether you are using a kit or building your own design.
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You should pick the proper location for your greenhouse. This should be a clear, sunny spot on a nice level location. The ends of the greenhouse should be situated facing north and south.
This is always a major decision when getting a greenhouse. The rule of thumb is – go one size larger than you think you will need. We are, after all collectors and experimenters. We may see the perfect plant at a sale that we just can’t resist. Or, we may find our next best go to variety of tomato or other vegetable that we just have to grow this year. Try to either mark out on your land how you think your plants will be arranged, or do this on a piece of paper. Consider whether you will be having raised beds, containers or hydroponic systems.
Will you build your frame using pvc pipe or galvanized pipe?
If you are using pvc pipe you should use schedule 40 pipe. The simple way to do this is to place a 3′ piece of rebar (sticking out of the ground 12″) where the ends of the hoops will be. Two people are needed for the next step. Place each end of the pipe over the rebar and make your hoop. Your hoops should be placed 4′ to 6′ apart. You will need to use purlins for your frame as well. These are what hold the pvc hoops together. If you skip the purlins you will just have a row of hoops with a cover over them. There is not much structure to this. A minimum of 3 runs of purlins should be used running from one end of the greenhouse to the other. Usually you have one right in the center of the greenhouse with one run along each side where the greenhouse is starting to “bow”. You can use special pvc fittings to tie these together. Most people will use treated lumber to run along the bottom of the long sides of the frames. You can frame out your ends with pvc or with wood. You can build your own door using pvc for framing, or use a purchased (or recycled) wood door. Please note: This style of greenhouse should not be used in high snow load areas. There is a tendency for this type of structure to collapse under heavy snow loads.
Galvanized Pipe –
There are pipe benders available to make specific width of greenhouse bows. Choose the appropriate one for your needs. You will install ground pipe 2′ into the ground with 2′ above the ground. Install your hoops at 4′ or 6′ increments. Install your purlins. You can use a board at the bottom of the sidewalls. The process is basically the same as with the pvc pipe, just different materials. The end walls can be framed out of wood. Although this structure will obviously not have any snow or wind rating, it will be stronger than the pvc frame.
Choosing Your Cover :
There are several different types of covers. The worst choice you could make is going to the box store and buying a roll of film off the shelf. This is great film, but it is just not designed to be used for a greenhouse. There is no UV protection on it. The sun is what breaks down the material. You will be lucky to get one year out of this type of covering. The most commonly used material is a 6 mil, 4 year greenhouse polyfilm. This means that the film is 6 mil thick with a UV covering rated for 4 years. There is also a reinforced polyfilm covering. It has a rip stop feature that will stop a tear once it hits the reinforced cording.
Single vs Double Cover:
You can use either one layer of polyfilm, or a double layer of polyfilm. For the double polyfilm a blower will add air between the layers increasing the insulation factor of the covering. Most people even say that they feel that this makes the film more resistant to tears because it makes it tighter.
Fastening Your Cover:
There are several ways to fasten your cover to the greenhouse. The piece over the top should go from ground to ground.
You can use batten tape to fasten the film to the bottom boards. You will place the batten tape over top of the cover and staple through the tape and the cover. Be sure to have your film tight, but not to taught. An overstretched cover has a tendency to tear.
This is a 2 part system consisting of a metal base (kind of like a c configuration) with a w wire or wiggle wire. You can fasten the base to your side boards. The base will also bend enough that you can fasten it to your end walls. Pull the cover over top of the base and work the “w” wire in with a wiggle motion. This is a good secure fastening system and will work well with a double polyfilm covering.
Don’t forget to address ventilation. Most people will frame out an opening in the front walls and back walls for exhaust fans or intake shutters. The exhaust fan should go up high in the back wall with the intake shutters down low on the opposite walls. These are usually wired to one thermostat so that they come on at the same time. You may choose to go more low tech and use a roll up curtain along both side walls.These are also available as solar powered systems which require no electricity.
There are times when a heater is not necessary for a hoop house. It depends on the type of crops you are growing and what time of year you are trying to grow them. Cole crops can be grown in hoop houses in the winter often without any supplemental heat at all. On the other hand, if you are trying to grow tomatoes or peppers in the winter you will need supplemental heating.
Building your own polyfilm greenhouse will be a rewarding experience not only while you are building it, but also while you are using it to grow your own crops.