Build A $15 DIY Garden Cold Frame

November 19, 2024|The Rusted Garden|

A garden cold frame will extend your growing season later into the fall and allow you to start growing sooner, come spring. In some gardens, they even extend the growing season through winter. Cold frames can be expensive like the one shown next to the DIY cold frame. That polycarbonate frame cost well over $200 but the DIY version only cost $10-$20 to build.

Materials

Materials needed to build this DIY garden cold frame are pretty basic. Greenhouse plastic that has a thickness of 3 mil+. You can find greenhouse plastic on-line with mil thickness ratings. A thicker painters tarp (from any store) can be used a substitute to decrease costs. Six post and some rope to create the frame and bricks or similar to weight the sides down, finishes off the materials list. Post heights will vary based on your design. Keep in mind they should be sunk into the ground a good 12 in/30 cm.

  • Option 1: Greenhouse Plastic 3 mil (or more)
  • Option 2: Thick Painters Tarp
  • Stakes or Posts (6) Sized to Your Design
  • Rope
  • Duct Tape to Cover Sharp Post Points

General Build

The skeleton of the cold frame can be designed with variable heights, widths, and lengths to meet your gardening needs. The measurements of this bed are 48 in/122 cm long, 33 in/84 cm wide, and 18 in/46 cm tall, at its center point. The frame is shaped like a standard housing roof. The center green metal post is the highest point, at 18 in/46 cm. The peak allows water to run off the ‘roof’. The wooden stakes are 12 in/30 cm high and are spaced about 16 in/40 cm from the center post.

Tying them together with rope creates the frame to hold the plastic. If water doesn’t run off and pools, place a small hole in the roof where it pools to allow drainage. Duct tape or a cover should be placed on any sharp posts so the plastic is not punctured.

Measuring the Plastic

The most important part of this DIY design is to measure the plastic correctly. I used 3 mil greenhouse plastic. Notice the 3 arrows. The width of the plastic needs to include 24 in/60 cm at the base to overlap the ground and create a place for the plastic to be weighted down. Measure up the small post and from the top of the smaller post to the top of the center post. Measure both sides. Double your measurement and you have the width of the plastic.

The length of the plastic also needs to include 24 in/60 cm of ground overlap and the height of the center post. This is needed for both sides. Again, double the measurement. These measurement will provide ample coverage for the frame and plenty of ground overlap to secure the plastic down. The cost for this project will vary based on the size of the cold frame and from where you source your materials.

Garden Cold Frame Uses

One question to ask is ‘what will I be using the garden cold frame for?’ As the answer will dictate the build design. A cold frame that is lower to the ground stays warmer longer and more efficiently manages temperatures. A cold frame works by both keeping in the warmth of the day and by using the warmth of the earth at night. The higher the top of the cold frame, the less efficient it is in keeping the space warm during the freezing nights. Notice I mulched the bed of the frame, as I will be growing plants in containers and flats.

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My goal is, a form of winter sowing, to grow perennial plants and seeds starts for the following year. I’ve already seeded up about 100 containers. If I were growing food directly in the ground, I would not put down mulch. Open soil is best for direct seeding. Prepare the earth as needed for growing. The height of the cold frame would depend on what type of crops are being grown. Crops like radishes, spinach and lettuces would do well with a lower ceiling. If I wanted to grow kale, collards, or other taller brassicas, I would need a higher ceiling.

You can find the video for this cold frame build on my YouTube Channel: The Rusted Garden. I have over 2,000 garden videos on just about every subject.

Another subject and video that may interest you is How to Grow Grocery Store Garlic in Containers. Part of my simplified budget gardening series for new gardeners.


Good Luck in Your Gardens,

Gary – Please Follow Me on YouTube: The Rusted Garden