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An Inexpensive Easy-to-Build Greenhouse

A greenhouse is very useful in the gardener’s set of tools. Being able to get plants started in a controlled environment is one of many benefits. Greenhouses come in many shapes and forms, from simple to very elaborate. I have contemplated building a greenhouse from time to time, but the cost of a more permanent structure has always been a deterrent. A few years ago I decided to give it a try without the big investment. One way to get started on a budget is to build a simple greenhouse out of low cost materials called a hoop house.

A hoop house is a round tunnel-shaped greenhouse made from PVC pipe, a small amount of lumber, and a plastic film covering. There are plenty of plans on the internet and some hoop houses can get pretty elaborate. Here’s a link for a much larger one on the Mother Earth News website. I built my first hoop house for less than $100 in materials. I figured it was worth a try. If I could keep the cost that low, I wasn’t risking much other than some time if the whole project turned out to be a failure. Here’s how I did it.

My ideal space was right next to the garden and workshop. Since I was a little concerned about how well it would stand up to high winds, I built it with one end attached to my workshop. The overall footprint is 9 feet wide by 12 feet long. The bottom of the structure is made up of a rectangular band of pressure-treated 2x6s in the same 9’x12’ dimensions. One end is attached directly to the side of the workshop building. The spine is constructed of PVC pipe. I used 1” schedule 20 PVC which is typically used for lower pressure applications like irrigation systems. The thicker schedule 40 is stronger and would be better for a larger hoop house. I found the thinner schedule 20 pipe was easier to bend to the necessary radius for my smaller design.

The PVC Spine Assembly

The PVC Spine Assembly

After constructing the 2×6 band, I assembled the PVC structure as shown in the drawing. I built it flat on the ground. It is important that the length of the center section is correct so make any adjustments by changing the length of the last 22.5” section before cutting and gluing it. The 20’ width was perfect for our 9’ wide structure once they were bent. When the cement dried completely, it was time to stand it up. This part takes at least two people and three is even better because you have to bend the pieces to fit while supporting the structure. We started on the end that attaches to the workshop. If yours is free-standing, you’ll want to start on one end. Get your screws, conduit clamps, and cordless screwdriver ready. Bend the two opposite ends of the first section of the spine to a half circle and hold against the outside of the 2×6 band. If you have a third person, have them hold the opposite end of the spine assembly up in the air so it is about level. If not, use something like a step ladder to support the end. Fasten the PVC pipe against the band with a clamp and 2 screws attached at the center of the 2×6 vertically to hold the PVC flat against the wood. Then do the other side. Keep working your way down the spine by attaching the next 2 pieces until they are all fastened. Make sure the spacing on the bands is the same as the spacing of the center spine so the curved pieces stay fairly vertical. Your ribs should be 24″ apart so make marks on the band at 24″ spacing to line it up.

PVC Attachment to the Band

PVC Attachment to the Band

Completed Spine Attached to Band

Completed Spine Attached to Band

The next step was to build the end structure for the door. As you can see in the picture, ours is fairly simple. I like to use the metal mending plates to hold the wood pieces together. The PVC on the end is fastening to the wood frame with some metal straps. The door is a simple rectangular structure with a diagonal cross-brace. I’m sure there are better ways to do this, but mine was quick to put together and has held up for four years so far.

The last step was to cover it. I used some 6 mil “clear” plastic from the local big box hardware store because I already had a box of it from other projects. Clear is a little misleading because it is somewhat opaque as you can see in the picture. I found it still allowed plenty of light through. It comes 20’ wide so it is a convenient width for our structure. I cut it to length leaving plenty extra to trim off later. The hardest part of my design was attaching it on the end by the workshop. A free standing hoop house would be much easier. I used the plastic conduit clamps and cut them to hold the PVC against the building but not cut into the plastic film. I pulled the plastic down over the first rib of the spine and against the building. The clamp is screwed to the wall through the plastic and holds the plastic tight along with the PVC which is held against the building by the clamp. On the other end by the door, I wrapped the plastic around the wood and fastened with screws and fender washers. The larger surface area of the fender washer reduces the chance of tearing the film. The door was covered with plastic the same way. It wasn’t pretty. It was bunched up in places, but it worked. Finally I secured the plastic along the sides with some scraps of wood approximately 6” square screwed over the plastic and into the band. The larger piece of wood reduces stress on the plastic and prevents tearing.

An optional addition I made was a pair of 2x6s running between the frame on the outer end and the workshop, attached on each end with joist hangers. This added rigidity and gave us some places to hang planters or herbs to dry. Finally when it was complete, I built plant benches on each side and the end from 2x6s and concrete blocks for supports. These are easily modified to suit various projects. For ventilation, I have a window in the wall of the workshop with a fan. I can open the door to the greenhouse and turn the fan on to circulate air. If you build yours freestanding, you could put a small door on the other end for ventilation.

Door and Inside

Door and Inside

Hoop House Covered

Hoop House Covered

I first built this in the fall of 2011. I learned that the cheap plastic film does not hold up well to sunlight and extreme heat. It started to fall apart after about 18 months. Since I don’t use it as much in the summer, I waited until the fall of 2013 to cover it a second time. Like clockwork, it fell apart after another 18 months. This past summer, I ordered some real greenhouse film that is supposed to last about 5 years. It was probably 3 times as expensive but that was an easy decision since it should last 3 times as long. I orderd a piece big enough to cut in half and cover the hoop house twice, so I have it covered until 2025 – pun intended!

I use it for starting seeds, propagating cuttings, raising black soldier fly larvae, and brewing compost tea. I even built my first small scale aquaponics system inside the hoop house. I store some of my tools in it so they are closer to the garden. It’s a lot more comfortable inside the hoop house on a cold sunny day in winter, not to mention the fact that I can work on plants and stay dry when it is raining. It isn’t a fancy greenhouse, but I use it all the time. Best of all, it was very easy and inexpensive to build.

Materials List:
16 10’ Schedule 20 1” PVC
2 Schedule 40 1” PVC Tee
5 Schedule 40 1” PVC Cross
14 1” metal conduit clamps
10 1” plastic conduit clamps
2 12’ pressure-treated 2x6s
2 10’ pressure-treated 2x6s
5 8’ pressure-treated 2x4s
1 box 1.25” coated deck strews
Misc metal straps
Plastic covering of your choice

Resources for this post:
Mother Earth News Hoop House Plans

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