Building a Cold Frame With Metal Bars

Large cold frame greenhouse

Building a cold frame greenhouse with metal bars is a project with spectacular benefits. Cold frames allow a gardener to get a head start on the spring growing season. Your metal frame will ensure this basic greenhouse will provide you season after season of gardening bliss. Your frame will be built with readily available electrical tools and supplies. You can build your cold frame greenhouse quickly, and correctly, on your first try.

Things You'll Need

• Metal conduit bender
• 20 feet metal conduit
• 6 Mil plastic

Instructions

1. Choose a location. A sunny area will provide the most benefit for your cold frame. Ideally, the grading should be nearly flat and close by. A part-shade location can be used if your yard does not benefit from full sun.

2. Bend the metal bars. Using a thin-walled metal conduit bender and thin-walled metal conduit, both available wherever electrical supplies are sold, bend the conduit bars into a large U shape. When complete, the ends of the conduit should be about 3 feet apart. The length of the bars will depend on how large you want the greenhouse to be. A 5-foot length will create an average-sized cold frame.

3. Insert metal bars into the ground. At your chosen location, push both ends of your bent conduit about 6 inches into the ground. Each successive set of pipes should be about 2 feet apart. You can construct a short 6- or 8-foot frame, or a lengthy 20-foot frame, depending on your needs and availability of supplies.

4. Wrap the metal bars with plastic. Carefully drape the plastic around the frame so there is sufficient excess plastic on all 4 sides. The plastic should be taut, but perfection is not necessary. Cover the excess plastic on all sides with rocks, bricks or any other heavy item.

Tips & Warnings

• Thin-walled conduit is commonly called electrical metallic tubing or EMT.

• Remove the plastic from the cold frame after danger of frost has passed.

• A more common version is made out of thin PVC piping---its cheaper and does not require bending tools.

• You can build a transportable cold frame by building a base out of 2x4s and drilling holes for the bars to slide into.

• If you build a cold frame in a full-shade area, it will not function as these greenhouses rely on solar energy.

References

• "EC&M": The Basics of Steel Conduit
• University of Missouri Extension: Building and Using Hotbeds and Coldframes

Resources

• "EC&M": The Basics of Bending Conduit