Weekend DIY Project: How to Build a Cold Frame

Use these step-by-step instructions to build a cold frame and extend your growing season.

| September 28, 2011

Release your inner DIY spirit with the full array of projects designed to help you increase your self-sufficiency in the book DIY Projects for the Self-Sufficient Homeownerby Betsy Matheson Symanietz (Creative Publishing International, 2011). After building the cold frame described in this article, look at the other plans in the book for implementing a composting system, setting up a root cellar, and building a beehive, among others. Each comes with photos to guide you through the complete procedure, making this a great place for beginning DIYers to get started. The following excerpt comes from Chapter Six, “Building a Cold Frame.”  

An inexpensive foray into greenhouse gardening, a cold frame is practical for starting plants six to eight weeks earlier in the growingseason and for hardening off seedlings. Basically, a cold frame is abox set on the ground and topped with glass or plastic. Althoughmechanized models with thermostatically controlled atmospheresand sash that automatically open and close are available, you can easily build a basic cold frame yourself from materials you probably already have around the house.  

The back of the frame should be about twice as tall as the front so the lid slopes to a favorable angle for capturing sunrays. Build the frame tall enough to accommodate the maximum height of the plants before they are removed. The frame can be made of brick, block, plastic, wood, or just about any material you have on hand. It should be built to keep drafts out and soil in. 

If the frame is permanently sited, position it facing south to receive maximum light during winter and spring and to offer protection from wind. Partially burying it takes advantage of the insulation from the earth, but it also can cause water to collect and the direct soil contact will shorten the lifespan of the wood frame parts. Locating your frame near a wall, rock, or building adds additional insulation and protection from the elements.  

TIP: The ideal temperature inside is 65 to 75 degrees Fahrenheit during the day and 55 to 65 degrees at night. Keep an inexpensive thermometer in a shaded spot inside the frame for quick reference. A bright spring day can heat a cold frame to as warm as 100 degrees, so prop up or remove the cover as necessary to prevent overheating. And remember, the more you vent, the more you should water. On cold nights, especially when frost is predicted, cover the box with burlap, old quilts, or leaves to keep it warm inside. 

Cold Frame Project Steps 

Find the complete list of tools and materials and a detailed diagram in the DIY Cold Frame Plans

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