DIY cold frames

this little green laughs at the frost!

Ha! Mache laughs at frost!

Our past couple of Mondays have been beautifully blue-sky clear and cold; waaay too nice to work indoors at a keyboard. Last week I got a wild hair to construct me some good old fashioned cold frames. After the spring of 2008 – which was more like a double dose of winter – I want the extra insurance against cold rain, bitter winds and late frost…and I’m talking last May!!!

I consider myself fairly resourceful. I also consider myself, uh, retentive. It’s not like I save string and nurture a giant rubber band ball, I’m just loathe to throw out something that might come in useful at some point in the next say, 50 years. I might be able to see the floor in our garage if it didn’t work out for the best so very often. Let’s just say if they ever have a household-repair Survivor series, I will NEVER get voted off the island. I even have a name for my disposition. I (proudly) refer to it as “Urban Hillbilly Chic”, and I’m sure it’s only a matter of time before I get my own line of lifestyle books, TV show, and attendant product line. Well, maybe not.


Anyway, as often happens when I get an itch to build something I start looking through our garage, carport and the scary, cobwebby room we blithely refer to as the “garden room”. Some of you may recognize the pieces of my cold frames as components of IKEA shelving units. Yep! It was like a cold frame kit once visualized with the right eyes. The old saying goes, the hardest piece to write is a set of instructions, but I’ll give it a go.

I made 2 frames but here are the directions for a single:


Position the  3 foot corner shelf pieces so that their longest side is down with the slanted end facing forward.  Screw two corner shelf pieces at right angles, horizontally to two 4 foot lengths of upright supports at the back of the frame to provide a brace at top and bottom.  Screw another 4 foot length across the front of the box to join the front edges of the frame.  See?


Things were going along so well I was moved to paint (!!!) the boxes which will help them withstand contact with moisture and soil.  Although frankly, these things have been in the “garden room”, believe me they’ve seen moisture and dirt.  I think they look quite dapper in barn red.


I know what you’re thinking…this is the draftiest cold frame in the history of cultivated gardening.  At this stage these frames would actually make good shade structures to protect young seedlings in the high heat of summer.  Yes, we do get heat in July and August, which is when I should be seeding fall crops.  Without cooling shade the tender sprouts and their shallow roots are destined to fry.

styro-insulationHowever, the heat of summer is a loooong ways off which is why I purchased rigid sheets of styrofoam insulation at the hardware store.  I had to break down and visit the big orange box store because our last sheet of insulation was turned into a Sumerian temple about 5 years ago…note to self: spray paint dissolves styrofoam!

I cut the 4×3 foot sheet into pieces to line the frame.  I choose to cut them a little on the large side so when I wedged them into place they would hold securely.  A little duct tape on the raw edges and to finish the corners and ta-da!  A fully insulated cold frame.  I cut 4.5 mil plastic sheeting to the width of the frame and long enough to fully cover and extend beyond the front.  Given our wierd artic weather pattern this year and the fact that I want to plant sooner rather than later, I doubled the plastic for extra protection.  My thinking is this will trap the greatest amount of heat and quickly warm the soil.  Once the season is underway I may have to make a second top with only a single thickness to allow more light to enter the frame.  (but I doubt that I will)

I reinforced the edges of the plastic with duct tape and stapled it to another 4 foot length.  This rests along the back of the frame.  The plastic can be rolled out to cover the box, partially removed to vent the inside or completely rolled up and secured at the back of the box for maximum exposure.

all tucked in and snug

all tucked in and snug

Top rolled back and a cushy bed of rich soil just begging for seeds

Top rolled back and a cushy bed of rich soil just begging for seeds

I was supremely excited to discover that these sturdy, light-weight boxes can also be stacked to form double height frames to house my peppers and basil this summer; it really is quite ridiculous how cold it can remain around here until the 4th of July!

Given that winter is intent on impressing us this year – we had spitting snow again yesterday – I’m thinking I’ll get a lot of use out of these babies.  I love it that they were almost FREE to construct; about $4 for the insulation and about $3 worth of plastic.   I know my shivering plants will appreciate their snug new clubhouse!

Cold Frame:  Consisting of a glass or clear plastic window hinged to an opaque bottomless box, a cold frame is placed directly over a part of the garden in effect creating an area of milder temperatures within.  The hinged lid opens to allow you to work with your plants and provides ventilation as well as protects against cold when closed.

Amend the soil within the cold frame with compost and plenty of organic material to boost fertility and provide drainage.  A cold frame is primarily in use during the fall, winter and early spring when the sun is at a lower angle.  To capture the available light and heat, site the frame where it will receive full sun between 9am and 3pm with the long axis of the structure oriented east-west.

The addition of a 6 to 8 inch layer of horse, chicken or rabbit manure turns the cold frame into a “hotbed” warming the soil considerable as the manure ages, a boon in cold climates.  Carefully monitor conditions within the cold frame to regulate temperature and humidity and water the plants as needed.

– From Growing Your Own Vegetables, Sasquatch Books, May 2009

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20 Responses to “DIY cold frames”

  1. Melanthia January 29, 2009 at 2:54 pm #

    That’s an impressive cold frame. My goal is just to make a simpel cloche by raiding my husband’s garage. Thanks for the tutorial!

  2. Rita Wright April 7, 2009 at 5:18 pm #

    Cool cold framing! Looks very nice also! Did you see my sis-n-law’s cold frames @ She uses windows, but seems to do very well with them.

    Thanks so much for the tutorial. You did a nice job. Would love to have you submit photo’s/blurb for my 52 states of gardens.

  3. Katxena April 7, 2009 at 5:41 pm #

    This is fantastic. Thank you for the instructions and pictures.

  4. August 17, 2009 at 1:33 pm #

    I too have a garden room. My room is in an unheated garage. It works great for tomatoes and peppers. I built a cold frame a couple years back and love it. The only thing I’m going to work on is temp control, thats my only problem. Any ideas?

  5. admin August 17, 2009 at 2:41 pm #

    are you trying to keep it warmer or cooler? For warmth you might consider putting in a plastic milk jug filled with water to act as a heat sink. The water absorbs the heat of the day and slowly releases it over the night to keep things a tiny bit warmer. To cool off, you just need to provide ventilation, prop the lid open or even poke holes in the plastic top. My experience, capturing the warmth is the most challenging. Good Luck!

  6. September 10, 2009 at 12:07 pm #

    I used water jugs on my smaller cold frame and it worked quite well. Right now I’m working on my large 8ft x 12ft cold frame / short green house. I’m thinking about running black plastic pipe under the soil and on the south facing wall and running a small pump. This would help me raise the temperature of my soil in the spring. I’m still planning on paper just waiting for my peppers to stop producing.

  7. November 10, 2009 at 7:29 pm #

    Right now I’m working on a floating cold frame, well that’s what I’m calling it. Its a cold frame that is extra deep and I lined it with plastic and filled it with water. I then use a plastic tote that floats on top of the water. I’m testing it now, I’ll keep you posted. Love the blog.

  8. Gavin November 26, 2009 at 9:47 pm #

    That’s a great idea to use styrofoam. It’s so versatile and can be cut into almost any shape really easily. That looks like a well-constructed cold frame. I’m working with styrofoam now to make a vertical garden. It’s the best material I think.
    .-= Gavin´s last blog ..Vertical Gardens from Green Over Grey =-.

  9. June Curts July 9, 2010 at 7:23 pm #

    I only grow plants and trees. I don’t know if it’s better to close the cold frame up completely around the fourth of July or not. It seems to be to hot , but if I leave it open it wants to dry out; and if I water it am I watering too much or too little. It’s in some sun. Would you be willing to give me some advice? Thank you for your time. Have a Blessed Day.

  10. lorene July 27, 2010 at 4:24 pm #

    Dear June… I’m embarrassingly late in replying! Forgive my lapse. I would definitely vent the coldframe on warm days – plants can quickly COOK – trust me, I’ve done it again and again. Anything you can do to raise the humidity inside the frame will slow down evaporation. Saturate the ground thoroughly when watering (I guess I should ask if you’re growing plants in the ground on in containers covered by a cold frame) I have the best luck with plants directly in the ground – then I simply transplant them when they are ready to move to their final garden position – either that or I simply remove the frame. If you are growing in containers – pot up your plants to the next largest size so they don’t dry out so fast. All my 4″ tomatoes went into gallon size pots and spent several weeks in the frame before being planted out in the garden. During that time, they were easier to keep watered and grew to a larger size than they would have in their little pots – worked great! Good luck!

  11. Margaret May 13, 2011 at 11:13 pm #

    I just built this coldframe this afternoon for my peppers and tomatoes. So excited! I’m enjoying the blog; thanks for all the useful information and entertaining stories!

  12. Lorene June 1, 2011 at 12:52 pm #

    Congrats on the coldframe and thank you for your kind words.

  13. Paul January 22, 2012 at 5:23 pm #

    really like the design of your coldframe, any ideas of something better for the environment and the possible contamination of the soil, other than styrofoam

  14. Lorene January 23, 2012 at 4:16 pm #

    The rigid insulation panel is effective and easy to source. You could also repurpose bubble wrap – any material that would insulate from the weather. Take a look at what you already have around the house and put it to use.


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