Building your own cold frame: the ultimate DIY guide
- Difficultyeasy
- Cost81-99 €
- Duration2–3 hours hour
Introduction
Here in the UK, we can’t always depend on the sun showing up when it is supposed to. Come rain or wind or snow, that doesn’t have to stop us from getting our green fingers stuck into some gardening. If you want to start the gardening season earlier or under less-than-ideal weather conditions, a DIY cold frame is the perfect solution.
Making your own cold frame is actually pretty straightforward and requires minimal materials. In our step-by-step guide, we guide you through everything you need and how to put it all together.
For further information, check out our “Planning & Background Knowledge” section. Here you will find even more tips and tricks to help you get the most out of your cold frame greenhouse.
Let's go – step by step: Build your own cold frame
By following these instructions and the material list above, you will end up with a small and sturdy cold frame measuring 150 x 70 cm. These instructions are also suitable for large cold frames, simply adjust the size of the materials accordingly.
A tip from us before we begin: Drill all holes with a wood drill bit to prevent splintering. Our 18V Power For All battery system makes it easy to seamlessly switch between all the power tools you will need to build your own cold frame. Simply unplug the battery and plug it into any other device in our range, all are fully compatible.
Be sure to pay attention to occupational safety at all stages to protect yourself and prevent accidents. Discover more about DIY best practices in our safety precautions guide.
Sawing and preparing the wood
Start with a hand-held circular saw or jigsaw. If you are unsure how to best use this equipment, be sure to check out our sawing video tutorial first. Cut to the following measurements:
- Boards for the box: 5x 150 cm & 5x 70 cm
- Squared timbers as ground anchors: 2x 25 cm & 2x 35 cm
- Roof battens for the support frame of the cover: 2x 150 cm & 2x 70 cm
- Moulding for the window frame: 2x 150 cm & 4x 70 cm
Take one of the short boards and draw a diagonal line from the top right corner to the bottom left corner. Then saw the board into two pieces along this line. These will define the incline of the cold frame window. See how to cut a straight line with a jigsaw in our video tutorial.
If not using pressure-impregnated wood, you will need to paint each part with a wood preservative glaze (see our guide on staining wood). The quickest way to do this is with a paint spray system and our paint spray guide will show you how.
Build the front and back walls
Screw the shorter squared timbers to one of the longer boards using a cordless drill, ensuring approximately 5 cm is protruding from the base. These will form the feet, which are particularly important if designing a so-called ‘warm cold frame’ (see “Planning & Background Knowledge” for more information). Place the second board flush with the first and screw onto the squared timber. Add a third and final board to the back wall only.
Install the sidewalls
Now attach two of the shorter boards to the squared timbers at either side. Finally, attach the two triangular boards you cut earlier. Fix the short end to the below board with a screw from above.
Make the roof
Use the screw brackets and the shorter screws to screw the four roof battens together to form a support frame. Then place the twinwall sheet into the frame.
Place one long and two short mouldings atop the upper length and two short lengths of the twinwall sheet, leaving a slight overhang for the side strips. Screw to the sheet from above. For added stability, fix the three reaming moulding strips to the sides.
Install the roof
Now screw the hinges to the box and roof and attach the handle. To protect the roof against strong gusts of wind or to prevent it from being opened too wide, we recommend adding two ball chains to either side. A piece of wood can be used to prop your DIY cold frame open when necessary.
Finally, hooks and eyes can be added to either side of the handle to keep the roof securely closed when not in use.
Planning & background knowledge for the DIY cold frame
A cold frame is a simple box that is open at the bottom and covered with glass or plastic sheets at the top. The cold frame acts as an insulator, much like a greenhouse, creating a warmer environment that is also protected from the elements. This helps seeds to germinate and young plants to grow unencumbered.
A DIY cold frame can be used to grow plants and vegetables further out of season than would otherwise be possible. For example, you could start sowing vegetables like lettuce, radishes, carrots and spinach as early as the end of February.
Local herbs such as cress or chives also feel just as at home in a cold frame as they do in a herb bed.
Advantages of a cold frame at a glance:
- A variety of vegetables can be grown even in cooler climates.
- Harvest time can be brought forward by several weeks.
- Harvest yields tend to be better.
- Plants with a long cultivation period can be grown in the cold frame and planted later in a bed.
- Young plants from the cold frame are more resistant than plants grown indoors. In addition, they harden quickly.
- In summer, the cold frame can be used for heavy feeders such as tomatoes and peppers.
- In winter, you can plant lettuce. The cold frame box is also a good storage place for root vegetables such as beetroot, celeriac, radish or carrots.
- A cold frame is cheaper and easier to build than a greenhouse.
- Thanks to its compact size, a DIY cold frame will fit most gardens.
What is the best location for a cold frame?
It is best to place your cold frame in a sunny area of your garden, with the glass roof facing south to maximise light exposure.
The box can be placed against a wall, over a plant bed or freely positioned. Alternatively, a DIY cold frame could be the perfect addition to a raised plant bed. Check out our DIY instructions for a raised bed made of pallets or, if you’re looking to maximise space in your garden, our raised bed with storage space could be just the thing you need.
What materials are suitable for a DIY cold frame?
The box and the roof of your cold frame could be made from a few different materials:
|
Material for the box |
Advantages | Disadvantages |
| Plastic |
|
|
|
Wood |
|
Can rot quickly if not properly treated and requires care |
| Stone |
|
heavy, not flexible |
If you want to build your own cold frame that lasts as long as possible, pressure-impregnated boards made of larch are recommended. For the cover, glass, acrylic glass, polycarbonate sheets, or twinwall sheets are all suitable. Twinwall polycarbonate, in particular, boasts fantastic insulation properties.
More DIY project ideas:
More from our gardening knowledge page:
What is the difference between a cold frame and a hotbed?
Once you have your cold frame, it is time to decide how you are going to use it.
A traditional cold frame is used primarily to protect seedlings and young plants from the elements while providing additional warmth in the same way a greenhouse does.
However, should you wish to create an even warmer environment for a particular plant species, a DIY cold frame can also be used to create something called a hotbed. By digging a hole beneath the frame and filling it with manure, plants are offered two heat sources – the heat generated by microbial decomposition and the heat from the sun.
In our guide on how to make your own cold frame, we recommend incorporating small feet to promote air circulation. However, in a hotbed, the base should be fully sealed to create a more enclosed space and maximise heat retention.
How do I properly care for a cold frame?
On very cold nights, you should provide additional protection for your cold frame. For example, by covering it with bubble wrap, fleece or spruce brushwood. On warmer days, it is important to ensure proper ventilation. This hardens the plants and prevents excessive heat build-up.
Automated windows are very practical: as soon as a certain temperature is reached inside, the cover opens by itself. As a rule, this is done via a pressure cylinder – a power connection is not required. If the sun is too strong, it is advisable to shade the panes with jute so that the tender leaves do not burn.
Costs of a cold frame – build it yourself or buy it?
Cold frames are commercially available as kits that already contain everything you need. Depending on the size and material, the cost can range from £40-400. Of course, it is almost always cheaper to build your own cold frame - especially if you use recycled materials (e.g., old windows or pallets).
More upcycling ideas for the garden
Are you passionate about sustainability and recycling? We highly recommend checking out some more of our upcycling projects!
For example, building an outdoor shelf from an old panelled door or making a rocking chair from discarded car tires are just two of our many upcycling projects for home and garden.