Project Guide

How to Build a Cold Frame

1
Measure and Cut Wood
Measure and Cut Wood

Begin by measuring and cutting 2″ x 6″ x 8′ wood to three pieces at 24″ and three pieces at 33″. These will be the sides of the cold frame. Cut 1 x 4 x 10 to three pieces at 36″ each and four pieces at 24″.

2
Secure the Wood with Screws
Secure the Wood with Screws

Use 3″ screws to make base of cold frame. Be sure to attach sides to front and back.

3
Cut Wood into Wedges
Cut Wood into Wedges

Diagonally cut a 2′ long piece of 2 x 6′ redwood. This will make your wedge on both sides.

4
Attach the Wedges
Attach the Wedges

Screw wedges to the top sides of the cold frame base using the 3″ screws.

5
Make the Top of the Cold Frame
Make the Top of the Cold Frame

To make the top of the cold frame, layout four of the 24″ 1 x 4 wood pieces and mark the places where you would make “halflap joints”. This is the part where a table saw would come in handy. Now glue the 36″ pieces to the 24″ long for the vertical pieces. This will make a nice flush cover for the cold frame.

6
Fasten Windows in Place
Fasten Windows in Place

Using the plastic screen clips attach all the 8″ x 10″ Lexan pieces underneath so you have a window. Attach hinges to top first and, when placed on the cold frame, screw the hinges to the cold frame base.

7
Add a Handle and Enjoy
Add a Handle and Enjoy

Screw on handle and place where your cold frame will get all-day sun. This is usually the south-facing side of your yard.


The finished cold frame will measure 36″ at the back, 24″ on each side, and 33″ on the front.

TIPS FOR USING THE COLD FRAME:

  • Raise the lid on your cold frame when the temperature hits 40 degrees F or above, so the heat doesn’t build up and cook your plants. Close it in the afternoon to trap warmth overnight. Use a stick to prop the lid open for ventilation on warm, sunny days. Cut notches in the stick so you can control how high to raise the lid. If needed, use a shade cloth to lower the temperature.
  • Don’t use glass if your area gets snow or ice. The built-up could break the glass.
  • Automatic vents aren’t recommended where snow and ice may keep the vent from operating.
  • Angle the cold frame so that the back is higher than the front. This helps capture more light and lets rain run off the roof.
  • For extra protection, position the cold frame next to a building.
  • For additional insulation, dig 6-8″ into the soil and build your cold frame partly below ground. If you’re concerned about flooding, add a layer of gravel underneath.
  • When the temperatures plunge to 20 degrees F or below, protect the cold frame by layering old blankets on top or use electrical heating cables.