Building a Cold Frame

Mar. 29, 2011

If you’ve started indoors from seed, you might be feeling as CROWDED as I am this time of year. Been planning on building a cold frame since winter, and now its time to work things out. It’ll be nice to give the plants room to breathe!

building a cold frame with shelving

Cold frames dont need to be pretty, expensive or even sturdy for that matter. I started with no cold frame designs or plans,  just a stack of 12″ shelving salvaged from a closed down foot locker and a handful of screws that were already in my pocket! They should disassemble easily to clear them out when the weather gets nice.

How to Build A Cold Frame:

My cold frames were as simple as screwing 4 boards together to construct the frame. Cold frames need a cover, so you could use old windows or plastic. Here I just used boards.

These cold frames need only to be functional, serving a very simple purpose. Keeping wind out and warm air in on cold nights.

building a cold frame

building a coldframe

Yep, its just a box. Covered with boards and an old blanket to keep the heat in. In the next week, I’ll be experimenting to figure out the best way to keep the heat in so that my overcrowded plants can be transplanted into pots as soon as possible and have a cozy place to stay until the weather is warm enough.

building a cold frame thermometerI threw the $2 thermometer in there and will be checking often against the outside temperature to see what makes the biggest difference on these crisp spring nights.


I have learned from trial and error, well many errors, that a coldframe with no buffer doesnt to much to retain heat. It worked well however to keep shield tender plants from wind and sunscald, which can be devastating to new plants trying to harden off. I did have to wait until the weather tamed to put all of the plants out. It was a safe bet when the overnight temperatures were consistently 45 degrees. And I built hoops with pvc and straps and used an old bedsheet from the resale shop. I like white bed sheets because they seem to let just the right amount of light in without having to shell out a lot of cash for shade cloth. I surely will be trying this again next year.

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3 Responses to “Building a Cold Frame”

  1. MamaNavyBrat says:

    We like to use old glass windows for the top and to build them at a 45 degree angle facing south so that the plants get maximum sun and heat. Like a miniature green house. We are debating adding removable old windows to some square foot gardening beds so we can skip the transplanting.

    • Trisha says:

      I did update the coldframe since this post, just not the website, haha. Yes, glass or plastic works so much better! We had the same idea for propagating new plants in our nursery. Actually the idea was in an old propagation book, they called it the ‘sun house’ and they propagated new plants right into the ground. Covered it with a hoop house (plastic and pvc) to keep the humidity levels high. I cant wait to try it. I believe windows would work just as well over your square foot garden. Ive seen them built with hinges and something to prop the window open. Have you ever tried clotches (clear 2 liter bottles) over single plants. I tried it with my tomatoes to keep them humid and protected from the wind. the plants looks amazing.

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