Building a greenhouse

EXPERT GARDENING ADVICE

I almost bought a greenhouse kit before deciding to build my own. The greenhouse kit I was looking at did not appear strong enough to withstand a heavy snowfall and I thought I could do it better. With that said, I started the greenhouse project which came together nicely and will last much longer than a greenhouse kit.

Design

I designed my greenhouse to accommodate 14 – 1040 flats and a center walkway that could be used for potted plants. I put together several different designs gauging what materials I had on hand and what I wanted to spend. The final decision was a 7X7 greenhouse, roughly 50sq. feet. I also wanted a door on each end for ventilation.

Materials used:

  • 20 pieces 1-inch galvanized electrical conduit pipe
  • 8 pieces 5/4 x 6-inch X 8-foot pressure treated decking
  • 1 greenhouse tubing kit to join pipes together (can be bought on eBay)
  • 1 roll of 12X50 6mil greenhouse plastic
  • 1 50X4 roll of plastic greenhouse floor
  • Assorted hardware: hinges, screws, latches

The above material cost approximately $350

Constructing the Frame

I had purchased a pipe bending jig on eBay in order to bend the pipes. Once I figured out the pattern, it took about 1 hour to bend the pipe. Each rib used about 20 feet of pipe. I purchased a greenhouse tubing connector kit (see picture) to help connect the pipe. The idea behind using these connectors is the greenhouse can easily be moved. The doorways are welded, and all the connectors have a spot weld in addition to screws to make it rigid. Wooden decking is placed around the base to provide an anchor to attach the plastic.

Attaching Plastic

Attaching the plastic can be tricky and best done with several people. First step is to attach the base of one of the sides and pull it over tight to the other side. Attach to base by first stapling it and then pinch it between a strip of wood and the base. You should pull it both ways to ensure there are no wrinkles and make sure it is centered so that you can wrap around the ends into the doorway. A wooden frame was constructed on the inside of the doorways bolted to the steel frame with self-threading screes. The plastic was then wrapped around the doorways and a thin wood strip was used to pinch the plastic in place. Regular T-55 staples are enough to hold the plastic in place before pinching it with wooden strips.

Building Doors

I measured the door opening and built my door from wood deck boards. I ripped them down to 3-inchs and assembled the doors with screws and steel braces purchased in the hardware store. On the inside of the door opening, I used a very heavy screen which made the doors rigid and plastic on the outside for starters. Since I have removed the plastic and replaced with removable windows to help with ventilation.

Conclusion

The result was a greenhouse, with proper care that will last a lifetime. It is anchored to the ground and can easily be moved (I have moved it 3 times) with minimum effort. I have many improvements over the past couple of years and overall very happy with the result.

Completed Greenhouse
Greenhouse frame construction