Winter Gardening Series #6 – Cold Frame Construction

Here at Stoney Acres we have three cold frames.  Each is 4 foot by 8 foot.  The plan I used came from “Four Seasons Harvest” by Elliot Coleman.  Although I did adapt the plans a little to my use and the tools I had to build them.

After the first snow of the year all my plants are snug and warm

Construction takes a while but is not overly complicated.  I used Douglas Fir to build my frames.  One of my frames is 4 years old, the other two are 3 years old and all seem to be holding up well.  I chose Douglas Fir mainly for cost.  Cedar and Redwood would both last a lot longer but cost about 4 times as much.  I hope the frames themselves will last 5 to 7 years and the lids much longer, we’ll see.  I would never use pressure treated wood because the chemicals used to treat the wood can leech out of the wood into the soil and contaminate my organic soil.

The frame box is just a simple box with a stretcher for stability

The wood itself represents only about 20% of the cost.  In 2012 dollars about $30.00 should cover it if you’re using the Douglas Fir.  The biggest cost is for the plexi glass I used.  Each 4×2 sheet costs about $25.00 and I needed four sheets.  So the total cost for each frame was about $130.00.  If you chose not to use plexi glass and instead just used 6 mil plastic your cost would be a lot less but you would also lose a lot of heat retention.

The sides of the box angle from 12″ down to 8″

 

The box itself is made up of one 2×12 and one 2×8 with another 2×12 cut in half and then cut at an angle from 12 inches to 8 inches.  The angled boards are the sides of the box and add the slope to the box.  I also added a stretcher to add stability and the stretcher also makes moving the box much easier.

The stretcher adds stability and is great for lifting the box

 

Some people paint or stain the wood but for me that just adds one more thing to have to take care of (repainting) and it also adds another chemical source to my organic garden.

This wood strip helps protect the box from soil rot

I did add a strip of 1×2 to the bottom of all my boxes.  This wood is super cheap only about $4.00 per frame.  It puts a layer of wood between the actual frames and the soil.  This will greatly increase the life of the frames.  When it gets old and rotten you can simply pull it off and add some fresh wood, in this way the wood on the bottom of your frame rots a lot slower.

The “lights” are each 2’x4′ and there are four on each box

The lids (or lights as they are called) are made out of 2×2’s.  I cut a small slot in the long sides of the boards to allow the glass to slip in and hold.  I then added some screws to each end to hold the glass in place.  My cold frames sit in a part of my yard that is protected from most winds.  Only once in 4 years have my lights actually blown off or even moved in the wind.  If you don’t have a similar spot in your yard you may also want to add some kind of hook or other latch to keep the lids from blowing off in the wind.

A slot cut with a table saw hold the glass in place

Over all each box took me about 3 hours to build.  I have built several frames for neighbors as well and now I’m quite the pro and I could probably get one done in two hours or so with a little help from my son.

The finished cold frame is ready to be placed on the beds

Now with all this said you don’t really need to go to this much work.  My cold frames are kind of the “Cadillac” version.  Many people will use an old storm door or window on top of a wooden frame.  I have even seen people have success with the box being formed by straw bales and the top just being 6 mil plastic.  The point is to protect your plants from the cold wind and freezing temps.  My design works well and looks good but it is not the only way to protect your crops.

 

Next time we will look at hoop houses.

10 Comments

  1. kitsapFG September 23, 2011 7:28 am Reply

    Wow that is really well done! Wish you were my neighbor… I would commission you to make a few for me. 😀

    http://www.modernvictorygarden.com/apps/blog

  2. 1stMan November 15, 2011 1:08 pm Reply

    What great instructions! Thanks for the valuable info. I can’t do it this year but I definitely see some cold frames in our future. Or at least that’s what I tell myself on the blog, ha. Thanks gain for sharing!!

    http://twomenandalittlefarm.blogspot.com/

  3. Jenny August 3, 2012 8:38 pm Reply

    Very nice work on the coldframe! We’ll be adding hoophouse this fall for winter garden and hope that it helps keep greens around longer.

    http://simplegardenmadeeasy.blogspot.com/

  4. Jody August 3, 2012 9:54 pm Reply

    I’m with you on the cold frame thing. This year’s labor (our first year with cold frames) has taught me that that glass is much, much better than plastic. But both of my glass lids were broken, either by storm or accident. They were recycled windows. So now I’m stuck with custom sizes. Do you go to widow manufacturers for your glass? Since I built mine to fit the custom size, I’m now required to ask for custom fittings. Will that cost me more? Hmmm. Maybe turning them into hoop houses this fall is the answer. I look forward to your post about them!

  5. Christie June 21, 2014 8:39 am Reply

    Do you have an estimate on how much it cost you to put them together? I want to build my own this year but am not sure what kind of investment it will be.

    • Mr. Stoney June 21, 2014 3:11 pm Reply

      Great question Christie, the most expensive part of the cold frames in the plexi-glass. When I built mine the cost for the glass at a home improvement store was about $20 a sheet, but that has gone up!! I think they are closer to $28 a sheet now. The type of wood you use will also affect the price. I used Douglas Fir which should last around 5 years, cedar or redwood would last longer but can be 2 or 3 times the price. So after all that, I would expect the 4 plexi-glass lids to cost around $115 and the wood and hardware another $35. So about $150 using Douglas fir. You could try to find the plexi glass at a commercial company and that could save you a few dollars a sheet.

  6. Pat October 18, 2017 8:51 am Reply

    Adding the 1×2 strips on the bottom is a wonderful idea! Not only for preventing rot on the actual frame but I have a major problems with moles and voles and those strips are my answer as t how to attach hardwear cloth to the bottom of my frames.

    http://facebook

    • Mr. Stoney October 18, 2017 9:10 am Reply

      Great idea! I hadn’t even thought of that. Of course Moles and Voles aren’t a real issue in our area. Glad I could help!

Leave a Reply