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Friday, October 1, 2010

Building a backyard greenhouse for $110

Our backyard greenhouse is finally finished - it took a few weeks -we spread it out.  Figuring out something from scratch like this can be frustrating and we found that when something went wrong (which it did) and needed to be redone (of course, it did) it was best for us to walk away for a few days or a week before starting again.  Better that than start bickering at each other, which happened a bit anyway.  Ah well, that's life!  :-)  But now, it's finished, and we are SO STINKIN' PROUD of ourselves!!!!!! 

Now you can learn from our mistakes and frustrations - here it is!  Directions to build your own unheated greenhouse - technically called a "hoophouse".  These directions will build a 20 foot long by 12 foot wide, and 6 foot tall greenhouse.  (20'x12'x6').  

I decided to build the frame out of low- cost PVC plumbing pipe.  It will also require some wood, hardware, and plastic sheeting.  You'll need a hacksaw for cutting and a good power screwdriver (we used a cordless drill with a screwdriver bit), a long measuring tape, and some sort of flags or markers you can push into the ground.  Here are the "ingredients":

  • 11 PVC pipes, measuring 3/4" wide and 10' long
  • 1 PVC pipe measuring 1 1/4" wide by 10' long
  • Plastic sheeting: 2 packages 6 mil thick 10'x25', 1 package 4 mil thick 8'x25' (you'll only use a small bit of the 4 mil package)
  • Wood: 2 pieces 2x2, 6 pieces 1x2 firring strips
  • Hardware: 3 packs mending plates, 1 package corner brackets, 1 package of 2 hinges, 2 packs 3/4" steel pipe strap
  • Duct tape, one large roll
To start, you'll need to plot out the spot where you want to put the hoophouse.  I placed mine over a portion of my already existing garden.  Look for the ground to be fairly level and somewhat sheltered from wind (the rear of mine backs up to a bush row, and there is a tree directly to the left and another about 30 feet to the right).  Now, most importantly, since this greenhouse is unheated, we need to get the most sunshine possible to hit it.  So, really, this greenhouse will be passive solar heated.  To do this, you want to orient the hoophouse so that the long side is facing the south.  In the winter, the sun is lower in the Southern sky, and you want the sun to hit the greenhouse for as much time each day as possible (of course, here in my area there is a lot of cloudiness in winter!).  If there are trees partially shading the greenhouse, remember that the leaves will not be on the trees in the winter, so there will be less shade and it will probably be alright, just so long as it will only be shaded for a small portion of the day.

After you've picked the spot, get the tape measure and wire flags.  You'll want to plot this out.  Decide where the door-side of the house will be and place a corner flag there.  Then measure 12' exactly across from this flag and place another.  This is where the first "hoop" of your hoophouse will go.  Keep measuring out until you've plotted out the entire 20 foot long house, or 5 hoops.

Next, I connected and glued together 2 PVC pipes using a tee-connector.  Then I pushed the ends of the PVC pipe into the ground where the flags were (you may need to dig a hole and water the ground where the pipe will go, to make it easier to push into the ground).  This seemed to work great until we bent & installed the hoops.
 But then a few days later, after we had put the plastic on, 2 of the joints popped out.  You can see them below, in the middle.  They came out of the tee-connector on one end. 

Back to the drawing  board.  We brainstormed at the local hardware store, and my husband came up with a very simple solution: buying a larger PVC pipe that could slide over the thinner ones.  We bought a 1 1/4" PC pipe and cut it into 5 pieces, each about 18" long.  Remember that the pipes came apart in the middle?  So we now have 2 pipes sticking out of the ground, no longer connected in the middle (no longer making a hoop).  Over one of these pipes we slid the newly made 1 1/4" PVC connector piece.  Next we took the two PVC pipes that were already in the ground but had come apart (Use 2 people for this!):  , standing on a ladder, and held them together while the other person quickly taped them together using duct tape.  Then we quickly slid the 1 1/4" pvc connector piece over the joint of duct tape.  Then we duct taped over it all, just for good measure - why not?   Like the first three hoops you see here:

Next, we added some stability by attaching wood to the sides.  I also wanted the wood as a place I could staple the plastic to, but that would allow me to roll up the plastic a few feet on the sides (meaning the plastic is not permanently attached to the ground, and can be lifted up until this piece of wood, so I could vent the hoophouse when it gets too hot in late spring or early fall.  We attached the wood to the pvc using 3/4" galvanized steel pipe straps.  It's basically a half-circle of metal with two screwholes on each side. These were connected on the inside of the hoophouse. We attached each piece of wood to the next piece using mending plates, on the outside of the wood.

Next came the plastic sheeting.  This was the most expensive part of this project.  For high wind and heavy snow areas, 6 mil plastic is recommended.  This is super thick and heavy duty, but also not cheap.  It cost us about $22 for a 10x25' roll, and we used 2 rolls.  We had to splice it together with duct tape.  Next time, I'm splurging on a huge roll so we don't need to use tape.

Before we attached the plastic, I made my rows and planted the fall seed.  I tied up the remaining tomatoes to make room for more seeds on the left side as well.

Next we put the plastic up, and my 2 older sons helped to water them with our new backpack sprayer.  This was purchased for use in watering seedlings on the farm garden, as I have no water access there.  But we decided to break it open and use it here at home.  It reminded me of the Ghostbusters backpacks...

Next, my husband tried making a door, but the 1x2" wood was splitting on him & causing him a lot of frustration.  I finally got him to nix the idea.

I remembered that we had a bunch of old storm windows in the attic.  One of the first projects we did on our old house when we bought it almost 10 years ago was to take off the old storm windows and replace them with storm/screen combinations.  The old storm windows were so beautiful I didn't want to part with them.  I'm glad I kept them - it made a perfect door.

My husband build the frame around the storm window, and attached it with hinges.  Next, we spliced even more plastic wrap over the frame so it would reach the ground (I used the cheaper 4 mil on this part), and I stapled it tightly to the frame.

I used a utility knife and cut off the excess.

For winter, I plan on using straw bales along the outside base, to sit on top of the plastic edge and also supply a bit of ground-level insulation.
Viola!  There you have it.  A homemade hoophouse.

It's toasty warm inside!

1 day after finishing the plastic installation, the outside temp was 75 degrees, and the inside temp was 94.5!

The cost of the hoophouse was just under $110.  The most expensive single item was the plastic sheeting, at almost $50.  The pvc frame cost $20, the wood was $12, the hardware & duct tape was $25.

A very similar hoophouse in a growers catalog that I receive sells for $1000.  Theirs is the exact same size, except it uses steel hoops.  So we built ours for 90% cheaper than ordering the kit.  Now you can see why we're so proud.  I love it when something comes together like this.

I'll have to keep an eye on heavy snow loads on top, maybe brushing off heavy snow if needed (even the tall steel hoophouses have been known to collapse under heavy, wet snow).  My goal is to keep the cold-tolerant crops from freezing.  I will be using row cover and possibly and interior layer of plastic over the crops as well.  My goal for this first year is to keep spinach growing all winter.  I'm in a zone 5 , right on the border with zone 4.   Think I can do it?  It will be fun trying!

Thanks for visiting the All Natural Mama blog, home to Wishful Acres Organic Farm!

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