Wednesday, November 20, 2013

Cold Frame How-to

Here is the plan drawing that we used for the four raised beds:

The basic raised bed is 7' x 4' and is constructed using 2 x 12 cedar boards with 4 x 4 cedar post in each corner (Note: Cedar is one of the best choices for wood that will be in contact with soil).

Pine sides fit into position like a jigsaw puzzle to transform the raised bed into a cold frame each fall. (Note: The cold frame box does not touch the soil and so we opted to build it with less expensive pine.)

Here you can see a photo showing all the sides in position without the obstructed view with the top in place: 

Because the sides fit together like a puzzle no nails are required to hold them in position. Any one of the side walls can be removed in a matter of minutes.

The final stage of the fall transformation from raised bed to cold frame 
involves the installation of three plexiglass doors.

1. Here you see the first completed cold frame door in position. We opted to use plexiglass for the doors rather than glass because it is not as breakable. Also for amateurs like us, plexiglass was a lot easier to work with! 

We were able to get readymade plexiglass panels (30" x 60") at the Home Depot which were almost the perfect size. We just had to shorten each plexiglass panel by 6 inches.

The door frames were made using four pieces of 1 x 2 Pine. To construct the door frames cut 2 x 54" lengths and 3 x 26.5" pieces (the competed door width will be 30").

2. The construction of the doors is very basic. Simply screw L-brackets into place at each corner of the door. The window's centre support bar is held in position with a metal T-bracket at each end. Then finishing nails are added at each corner for extra stability.

We designed the plexiglass panels to sit on top of each door frame rather than being inset (as in a standard window frame). We wanted any rainfall or snow to be able to slide cleanly off the surface of each door.

Now place your plexiglass panel on top of the frame and clamp it into position. You need to cut off the extra 6" overhang. Using a T-square and an Exacto knife score the plexiglass along the outside edge of the frame. Hubby carefully scored the line 6 times to ensure a good clean cut. 

4. Grab a scrap of wood and place it along the inside of your scored edge. Now press down on the overhang and it should snap cleanly free.

5. Attach the plexiglass to the frame with 3/4" #8 Robertson screws (3/4" Phillips will work just as well). We placed a screw approximately every 6.5".

 Just a couple more steps!

6. Now attach a handle to the centre front of each door. We used an inexpensive 5 3/4" handle.

7. On the back on the cold frame attach each door with two 3.5" T-hinges approximately 6" in from the sides of each door. These T-hinges are the one semi-permanent part of the cold frame that will have to be removed to dismantle the cold frame each spring.

Condensation on the inside of the plexiglass doors provides plants with moisture. 

The cold frame is not heated of course, and so during the winter it will get cold in there, but the enclosed structure will always be much warmer than the surrounding environment.


  1. Siento mucho lo de tus padres.Espero que pronto te encuentres mejor.
    Un fuerte abrazo.

  2. Beautiful are the garden and dog photos

  3. I'm envious, what a great resource to have in your garden. Sadly there is just no way we have room for a cold frame.

  4. Very nice! If we had a level area, I would put a raised bed garden....level and in full sun that is. Your directions make me want to give it a shot.

  5. Sorry for your loss. Thank you for sharing

  6. I am 73, so could i opt to leave the plexiglass as is and make my raised bed to fit it. Less measuring and cutting.
    Also, I have problems with groundhogs and mice during the summer. Wonder if they would discover my wasrm raised bed during the winter. Should I put a piece of wire cloth under the soil to keep them out?

    1. We made the plexiglass doors a size that would fit our pre-existing raised beds. You could do it in reverse and start with the sheets of plexiglass and make the raised beds the right size to fit the sheet of plexiglass.
      I don't have issues with groundhogs, but we do have mice and voles. So far no creature has made the cold frame a winter home. You could put a wire mesh under your raised bed, but I wouldn't put landscape cloth. Landscape cloth is not made with the most environmentally friendly materials, and presumably, you will be growing food in your cold frame so you don't want to use anything that can contaminate your soil.

  7. Is the plexiglass door frame attached to the raised bed or is it just laying on top of it? Beautiful cold frame, I'm interested in trying it for our garden.

    1. Hi Unknown, Please see picture 7 to find out how the plexiglass doors are attached to the frame. The three doors have to be unscrewed and removed each year.

  8. Thanks for the tutorial!

    If you used door hinges you could remove the pin to take them apart instead of undoing the screws. To fill an old screw hole, use a wooden match (the wood part) dipped in carpenter/white glue. After it dries, cut the excess off with an olfa knife. This will allow you to put a new screw securely in the same spot.

    1. Thanks for the suggestion. My husband worries that the door hinges would be too big, but it is worth looking into. Thanks also sharing your method for filling screw holes. My husband has used this trick too. A toothpick also works if you don't have a match.

  9. Do you have a template or approximate measurements for how you cut the sides to fit together? I can see some creative cuts in your photos and would love the chance to create one of these!

    1. I would love to have a plan drawn up, but that would mean hiring a draftsman. In the meantime, may I recommend the book Raised Bed Revolution by Tara Nolan. There is a plan for a cold frame with a plan, measurements, and a material list. I think you’ll find the project is very easy if you have basic carpentry skills


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