DIY Mini Greenhouse (Coldframe)

3 Materials
2 Hours

Put old windows to good use with this DIY mini greenhouse/coldframe, and extend your garden season!
diy mini greenhouse coldframe
Your first step is to attach the windows to the 1×4 board that will be the top of your coldframe. To do this, lay your windows on the ground with the 1×4 (cut to window length). Place hinges on windows and board, so you’re sure to have enough space for the windows to move once the hinges are screwed in. Mark screw holes in hinges with a pencil on wood. Once you’ve determined where each hinge will be, attach hinges with included hardware. 
diy mini greenhouse coldframe
Now stand your windows up (bottom edge resting on the ground) to determine how large of a “box” you want your frame resting on. If you want the coldframe to accommodate taller plants, you’ll want a box with less width. If you’re not worried about height, but would like a wider box to fit in more small plants, then spread your windows further apart. The idea is to play around with your attached windows and figure out what size space you’d like covered by your coldframe. (We settled on a taller frame, so I could use it for a variety of plants.) Once you’ve determined how you want your windows situated, measure the distance between the corners of the windows for your box width. Your box length will be the length of the window.
diy mini greenhouse coldframe
Using the width and length measurements you’ve taken, use the 1×6 cedar boards and create your “box.” Once you have your 4 sides (2 width wide boards, 2 length wise boards) attach them using L-shaped connectors. (This simple box you’re created would also be an easy way to make a raised garden bed.)
diy mini greenhouse coldframe
Using your 2×2’s you’ll now create the frames for the ends of your box. These will hold up your windows and 1×4 connector piece. First, cut pieces to attach to the ends of your 1×4 connector board. These pieces will have angled ends, so your windows will have a place to rest and not collapse in. Our pieces were 5 inches on the top and 6 1/2 inches across the bottom. Cut four pieces this size; you’ll use two now and two later. Once you have your pieces cut, screw one onto each end of the 1×4 board that’s attached to your windows. 
diy mini greenhouse coldframe
Now you’ll create the edges of your end pieces. (The end pieces of your cold frame are essentially triangles with flat tops. You’ve just attached the flat tops to your 1×4 connector, now you’re making the sides of the triangle.) For this, we cut 2×2 boards into 21 1/4 inch pieces with angled ends. You’ll need 4 of these pieces, two for each end of the frame. Since the 2×2 pieces will sit at an angle, you’ll need to cut the ends slightly, so they will fit flush against your top piece and your box at the bottom. Once you know the pieces fit against both the top board and bottom box, screw them into place. 
diy mini greenhouse coldframe
Because of the size and weight of the windows we were using, we also added pieces of 2×2 to the middle of the end frames. We cut two 22-inch pieces and attached one at each end of the frame, between the side pieces we’d just attached. (These pieces screwed into the 1×4 at the top and into the inside of the box end. (See above image.)
diy mini greenhouse coldframe
Almost done! For smaller windows, this next step won’t be necessary, but for additional support, we added angled 2×2 pieces to give the 1×4 connector extra strength. You cut these pieces earlier in Step Four. Take those two angled pieces you cut, and fit them between the 2×2 at the center of your end piece and the underside of the 1×4. Once you have them in place, screw them in. 
diy mini greenhouse coldframe
As a final step, attach handles to the bottoms of your window frames. This will give you an easy way to open your coldframe. And you’re done!
diy mini greenhouse coldframe
Your coldframe will be the perfect place to grow veggies and herbs and to start seedlings in the early spring!

Suggested materials:

  • Cedar  (Lowe's)
  • Galvanized screws  (Lowe's)
  • Sheet metal  (Lowe's)
The Kitchen Garten

Want more details about this and other DIY projects? Check out my blog post!


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