How to Build a DIY Cold Frame

Cold frames are small, portable, solar-powered greenhouses. They protect plants from adverse weather conditions like cold temperatures, excessive rainfall, and hail. Keep reading to learn how to build a DIY cold frame with simple, readily available materials.

Using a cold frame allows gardeners to conveniently start their cool-season crops earlier in the season. They’re also helpful for hardening off warm-season plants and extending the growing season later in the autumn. Cold frames are incredibly straightforward to build at home, primarily using repurposed materials.

How to Build a DIY Cold Frame

First, decide on the dimensions you want for your cold frame. Some gardeners use a cold frame to top raised beds in early spring. Others employ them as a free-standing mini-greenhouse that they can move around as needed. Customize your cold frame’s design and materials to suit your unique situation.

Materials

• Salvaged shower door or windows for lid (if unavailable, use polycarbonate or a sheet of greenhouse plastic)
• 2×6 lumber pieces for frame and walls (quantity and length depend on your intended size)
• 4 1×1 lumber pieces for corner posts
• 2 1×1 lumber pieces for lid supports
• Hinges (quantity depends on your intended size)
• 2 handles (optional)
• Screwdriver
• Wood screws
• Drill

Step 1: Build the Frame

To begin, cut your 2×6 pieces to match the dimensions of the cold frame’s lid. It’s helpful to design your cold frame so that the back is taller than the front to drain water and maximize sunlight hours.

Screw four 2×6 pieces together to make the bottom of your frame. Then, attach a vertical post at each corner.

Step 2: Build the Walls

Next, cut one of the 2×6 pieces diagonally to make two triangular pieces for the sloped sidewalls. Starting at the bottom, screw the sideboards to the corner posts, securing each 2×6 board with two wood screws.

For the triangular top panels, attach the narrow point to the board below with a vertically placed screw. Repeat at the front and back with more 2×6 boards to complete the box.

Step 3: Attach the Lid

Position your lid piece(s) on top of the sloped frame and mark where you want to place the hinges at the back. If you aren’t repurposing salvaged windows or a shower door, construct the framework for the lid and attach transparent or opaque greenhouse plastic or a sheet of polycarbonate.

For longer cold frames, use several hinges along the length of your cover to ensure that it’s secure. If you’re using repurposed windows that open to the sides, consider adding a horizontal support beam down the middle of your cold frame to support the lid pieces when they’re closed.

Step 4: Add the Lid Supports and Handles

Next, attach the lid support beams. First, place a 1×1 piece in the front corners on either side of the cold frame. Use small pieces of wood to create braces for holding the lid up at various heights.

Then, position one or two shorter supports in the middle or on either side on the front edge of the lid. These pieces keep the cold frame’s top just barely open enough for ventilation on colder days.

Attach the support pieces to the inside of the frame and lid with wood screws. Make sure that they’re just loose enough to move into position but tight enough to remain firmly in place when supporting the open lid.

If desired, add a horizontal handle to each end of your cold frame. Doing so makes moving it around your garden more manageable.

Build a DIY Cold Frame to Make Gardening Easier

Gardeners can accelerate their spring harvest by several weeks by using a cold frame. Similarly, cold frames can extend the growing season significantly in the fall and even throughout the winter in milder climates. You can design your cold frame to be mobile for use in various locations around the garden or build it as a permanent extension off of an existing wall or fence.

Do you have any suggestions or questions about making a DIY cold frame? Please share them in the comments! If you found this guide for building a cold frame helpful, please share this tutorial with your fellow gardening enthusiasts.