How to Make a Cold Frame

Cold frames provide extra warmth for plants, as well as frost protection, making this garden structure suitable for low-growing cool-season plants and seedlings.

Building a cold frame from recycled materials such as old windows and shower doors can be done yourself; there are various DIY plans for building such structures available online, from straightforward projects with automated opening sequences and lighting to more involved efforts with automated opening sequences and other features such as automated opening sequences.


Cold frames are simple garden structures designed to provide extra protection for frost-sensitive plants or cuttings that have roots. Consisting of boxes with transparent lids, cold frames can be made out of almost anything that provides enough solidity and support to protect crops from winter winds; wood panels and old windows are popular choices but bricks, polycarbonate sheets, straw bales or PVC pipes could all work too – including blocks of concrete! When combined with heavy fabric row covers they provide another level of defense from freezing winds and snowfall.

If you decide to build your own cold frame, it is essential that the location receives plenty of sun and heat throughout the day. A south-facing location is best as direct sunlight warms both soil and air inside the frame; otherwise try sheltering it from harsh winter winds with buildings or structures nearby. To further increase effectiveness, add additional insulation on its north, east, and west sides such as manure, compost, straw or shredded leaves – these could all provide beneficial heat-retaining layers.

Some gardeners utilize electrical heating cables to create a “hot bed,” raising the temperature inside of their frame by several degrees – especially helpful in northern climates where late spring frosts may occur frequently.

Cold frames provide the greatest benefit to gardeners by extending your gardening season by providing frost-free shelter for tender plants and cuttings that require protective warmth to grow successfully. You can grow many types of vegetables, flowers, herbs and shrubs until it warms up enough for them to be transplanted back into your garden. Cold frames also make an excellent space to harden off annual flower and vegetable seedlings started indoors and can even serve as an affordable greenhouse alternative when propagating new plants from cuttings – plus they’re easy to build!


Wood will be essential when building a cold frame. Its structure may take the form of a four-sided box without bottom, greenhouse, raised bed or even straw bales and soil; whatever its shape, however, solid materials such as solid wood must be used with transparent top (preferably glass or plexiglass) to allow sunlight in and maintain warmth levels within. Other possible materials used as sides include concrete blocks, bricks polycarbonate material concrete blocks or straw bales mounded upon them for additional support.

No matter the material chosen for your frame – wooden battens, planks or plywood – it should be at least 2 inches thick to provide sufficient support. When possible, try salvaging materials rather than purchasing new; doing this will save money and reduce landfill waste, while it can be fun as well. Skips at houses undergoing renovation may contain window frames or shower doors which could become cold frames; old garden tools could even be repurposed into frames by drilling through their handles and attaching them securely via screws.

Once your cold frame is built, it should be placed where the sunlight will directly hit it in winter – ideally facing south. A sheltered location will help to block wind while protecting it from rain and frost; you could mount one against a shed, garage or greenhouse or on your home or deck for optimal results.

Make a more permanent structure using bricks, cinderblocks and old windows to build a garden cold frame that will last all year round. This option is especially helpful for people who want to extend their growing season and harvest vegetables and flowers into winter without being exposed too directly to nature; perfect for cold climates! Additionally, this structure can easily be moved from place to place when required.


Cold frames are simple carpentry projects designed to extend the growing season by harnessing passive solar heating techniques for protecting gardens during the winter. At their core, cold frames consist of boxes with clear lids designed to allow sunlight to enter while trapping its heat inside for 5 to 10 degrees of additional warmth in comparison with surrounding soil temperatures. Their lid usually lifts for access by gardeners tending plants growing within, providing access for tending purposes by gardeners. Designs range from modified 2-liter bottles through sophisticated structures featuring automated opening sequences, lighting features and self-watering capabilities for gardening!

There are various DIY cold frame plans available, from the very simple to sophisticated structures that can be completed for less than $100. Many plans call for building a wooden box which can then be placed over garden beds to form an instant greenhouse; alternatively you could also construct one out of an old window or existing raised bed.

One popular design for creating a cold frame is to construct a small box and cover it with polyethylene sheeting, creating an inexpensive yet effective method of starting cold-tolerant crops in early spring, hardening seedlings before transplanting, protecting tender perennials or overwintering tomatoes and other vegetables. A DIY cold frame like this one can be constructed from materials like wood, metal or concrete and makes an excellent project for beginner gardeners.

Another quick and simple DIY cold frame design uses double-pane windows purchased from Habitat for Humanity ReStore joined together with jute twine tied around each corner tack for easy construction. This arrangement is particularly efficient, as you only need to lift its lid occasionally to add water or provide ventilation.

There are also more elaborate DIY cold frame designs that resemble greenhouses, though their assembly requires more skill and expertise. An example is this plan which combines the style of a hoop house with a wooden frame. Such frames provide sufficient warmth to enable emerging plants to flourish before frost sets in. This type of cold frame is ideal for starting seeds during fall or spring planting seasons as it provides adequate time for them to mature before being affected by frost.


Cold frames serve to extend and protect crops that would normally be vulnerable to cold winter weather, while also increasing productivity. Construction material options vary from bricks or cinder blocks to concrete, plastic lumber or straw bales depending on climate factors in which you intend to place your cold frame.

Wood is often chosen for building structures, though any treatment with creosote or similar chemicals should be avoided to avoid contamination of soil and plant life within. Untreated wood should be painted to reduce decay and enhance aesthetic appeal – white latex paint will reflect sunlight while darker hues can absorb its heat and radiate it back inside the space.

As it’s essential that the structure be well insulated, using plastic or fiberglass on its bottom surface should help insulate it and keep heat inside while protecting soil from frost. Installing a vent in the lid is also recommended to release collected heat when necessary and prevent overheating; placing an indoor/outdoor thermometer within your cold frame so you can monitor and regulate its temperature as needed is also beneficial.

Cold frame lids should be constructed of clear material that allows you to easily lift it when adding or taking out seedlings and cuttings from inside or outside the frame. Repurposed windows are often used, though polycarbonate or glass sheets also work. It is best to position the lid so snow and debris don’t build up on top and block light sources.

As part of building hinges for your lid, it’s best to pre-drill screw holes beforehand to prevent wood splitting when tightening screws. Furthermore, tightening hinges too much could cause them to crack under pressure; once attached they can be sealed with clear waterproof sealant to further protect wood surfaces.

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