Build a Simple Cold Frame

comments (5) August 14th, 2008

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Download the plan, a materials list, and instructions for building this cold frame.
This cold frame can give you a 12-month growing season.
A layer of 2x2s atttached to the bottom keeps the cold frame itself out of contact with the soil.
Download the plan, a materials list, and instructions for building this cold frame.Click To Enlarge

Download the plan, a materials list, and instructions for building this cold frame.

Photo: Vince Babak

My cold frame, consisting of a bottomless box and glass frames, called lights, is simple to build and designed to last for years. Use rot-resistant wood such as cedar, cypress, or red­wood.

The waste strips along the bottom keep the frame off the soil. When the waste strips decay, you replace the strips instead of the entire frame.

  Download the project plan.
  Cold Frame Gardening
Learn what you can grow and when to plant it, then enjoy fresh food all winter long.
The lights have small wood stops at both ends. The stops keep the glass from sliding and enable water to run off freely, preventing ice build-up and rot.

To make a light, you’ll need a tablesaw for cutting grooves and ripping stock lengthwise. Glazed with glass, each light will weigh around 35 lb., heavy enough to stay in place by itself, but too heavy to be raised by an automatic venting arm. Glazed with a lightweight, insulated glass substitute like Polygal or Lexan, each light can be lifted with a venting arm (such as the Univent control from Charley’s Greenhouse & Garden), but will also need to be secured with hinges to keep it from blowing off in a wind.

Materials list
Each 8-ft. x 4-ft. frame requires:

• 2 8-ft. x 12-in. boards
• 1 8-ft. x 8-in. board
• 1 4-ft. 2x2 for the brace
• 3 8-ft. 2x2s for the waste strips around the bottom
• 3-in. galvanized drywall screws
• 2-1⁄2-in. drywall screws or 8d nails for attaching the waste strips
• 4 2-ft. x 4-ft. lights

Each light requires:

• 2 4-ft. 2x2s for sides
• 2 21-3⁄4-in. 2x2s to rip for crosspieces
• 2 scraps for making the stops
• 3-in. galvanized screws
• 1-in. galvanized screws
• 1 46-1⁄2-in. x 22-3⁄4-in. sheet of glazing material (double-strength plate glass or polycarbonate glazing

by Eliot Coleman
August 1996
from issue #4 

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posted in: Projects, fall garden, cold frame

Comments (5)

Crocheeraablo writes: Lovely!!!!!
Posted: 5:45 am on May 11th
yatesinc writes: I'm not to knowledgable on the subject but I do know that plants, mainly trees do expel tiny amounts of heat. So I am wondering if there are any cold hardy plants that tend to expel more heat then others. So including some in your cold box may add a little more warmth. Just a thought.
Posted: 11:19 pm on May 3rd
yatesinc writes: I live in Maine and in the Winter at times it can reach 20 below zero. A trick I thought of involves a mylar survival blanket.

Line your box with the mylar, rather then the bare wood absorbing heat and expelling it to the cold air outside, the mylar will keep the heat and the suns infrared rays bouncing around inside your box.

If you wanted to go further you could dig out your box about 12" and then line the hole with mylar, put your soil back in over the mylar, this will keep more of the cold from the ground out and more heat in. If it's a raised bed it's much easier.

It can save you a few degrees.
Posted: 11:16 pm on May 3rd
teteapotre writes: look in to hotbeds--they are cold frames with electric heating blankets underneath the soil/based.

there are also passive solar heating options, with things like black barrels to retain the heat of the day...
Posted: 3:36 pm on August 7th
dulcimer05 writes: I live in Central Georgia and experimented with a cold frame two winters ago. My "cold-frame was a three foot tall, six feet long 2x2 box with visqueen plastic sheeting for a covering. I used a 100-watt trouble light to provide heat since the winter temps were well below freezing for a month or more. I put all my yard flowers and bushes in it and managed to save about half of them. Has anyone ever tried plugging in an electric blanket around the plants to increase the ambient air temperature in a small cold-frame?
Posted: 8:31 pm on August 3rd
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