Build A Window Sash Cold Frame

Protect your garden by building this simple, yet effective window sash cold frame.

| September 2018

  • window sash cold frame
    Window sash cold frame. Old window sashes are ready-made tops for this style of cold frame. If you don’t have any spare sashes, you can frequently find overstock for sale at your local lumber store.
    Photo by John Gruen
  • window sash cold frame corner close up
    With a cold frame, the danger of heat and dehydration is far greater than the danger of cold, even during the early spring and late fall when you will be using your cold frame the most.
    Photo by John Gruen
  • window sash cold frame illustration
    Using a cold frame can extend your growing season four to six weeks on each end, here is a good model that is straightforward to build.
    Photo by Michael Gellatly
  • woodcutting diagram
    Woodcutting diagram for building the window sash cold frame.
    Photo by Michael Gellatly
  • book cover
    “The Vegetable Gardener’s Book of Building Projects” by the editors of Storey Publishing is a guide for readers that includes 39 building projects for aiding in planting, growing, preserving and relaxing in gardens at a reasonable cost for beginners and experienced woodworkers.
    Cover courtesy Storey Publishing

  • window sash cold frame
  • window sash cold frame corner close up
  • window sash cold frame illustration
  • woodcutting diagram
  • book cover

The Vegetable Gardener's Book of Building Projects (Storey Publishing, 2010) by the editors of Storey Publishing is a collection of 39 building projects designed to help transform a modest vegetable garden into a model for comfort and efficiency that is still affordable. Whether you are an experienced builder or just starting out there are projects for every level which lead to functional and attractive projects that will encourage your vegetables to thrive and grow long after the season ends.

You can purchase this book from the Heirloom Gardener store: The Vegetable Gardener's Book of Building Projects.

Using a cold frame can extend your growing season four to six weeks on each end. Here is a good model that is straightforward to build, small enough to reach into easily yet large enough to help in your gardening, and a great use for any spare window sashes you may have on hand.

Materials

Lumber

  • 2"×4" cedar (10' length)
  • 1"×6" cedar (12' length and 16' length)
  • 1"×8" cedar (6' length)
  • 1"×10" cedar (8' length)
  • Two tomato stakes (27" lengths)
  • Two 30"×29" window sashes

Supplies

  • Two pairs of 3-1/2" ×2-1/2" exterior hinges and screws to go with them
  • 2" exterior wood screws (70 or so)
  • Two 1-5/8" exterior wood screws
  • Tools
  • Tape measure
  • Pencil
  • Carpenter's square
  • Wood saw
  • Power drill
  • 5/32" twist drill bit
  • Driver bit to match screws

Temperature

With a cold frame, the danger of heat and dehydration is far greater than the danger of cold, even during the early spring and late fall when you will be using your cold frame the most. Remember that even on the coldest winter day, the bright sun can quickly push the temperature in the cold frame up to above 75 degrees–80 degrees Fahrenheit (24 degrees–27 degrees Celsius), which should be the maximum. Provide a system of props so that, if there is a chance of overheating, the sash can be raised. Unless prevailing winds blow directly into the cold frame, there is little danger of damaging plants through chilling them.



Cutting the lumber.

  1. From the 2"×4", cut three 19-1/2" lengths A and three 12-1/2" lengths B for the upright posts.
  2. From the 1"×6", cut three 59-1/2" lengths for the lower front and back boards C and five 25-1/2" lengths for the side and center boards D.
  3. From the 1"×8", cut one 59-1/2" length for the upper front E.
  4. From the 1"×10", cut boards for the upper back f and angled upper sides g as specified in the cutting diagram at right.

Constructing the cold frame.

  1. To start, build the side panels using the taller upright posts A for the back corners and the shorter upright posts B for the front corners. The angled upper sides G will create a sloped top that both permits rainfall to run off the cold frame and allows for maximum sunlight to reach the plants inside.
  2. Screw the front boards C & E and back boards C & f to the ends of the side boards D & G to create a box. Then attach the center posts A & b to the inner box and screw the ends of the center board D to them.
  3. Position the window sashes on the frame so that the tops are flush with the back wall (they will overhang the sides and front of the frame a bit), and mount the hinges.
  4. To provide ventilation, use the 15/8" screws to attach the bottoms of the tomato stakes to the inner front corners of the frame, as shown. The screws should be loose enough to allow the sticks to pivot forward when you want to prop the frame open.

Builder's Tip

The dimensions for this style of cold frame revolve around the window sashes you use. If yours are a different size than the 30"×29" ones specified here, you'll have to modify the frame accordingly. Either way, attaching the sashes with hinges that have loose pins will allow you to remove the windows easily if needed.






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