How to Build a Cold Frame

Always wanted (or could really do with) a greenhouse but don’t have the space?

A cold frame could be just the alternative solution you are looking for. Built as a simple structure, cold frames act almost like a miniature version of a greenhouse, utilising solar energy and insulation to make your own little microclimate in your garden. They create an optimum environment for hardening seedlings, starting seedlings earlier and even extending the growing season.

Why Build a Cold Frame?

A cold frame offers a variety of fantastic practical advantages. Firstly, you can easily move a cold frame into various positions which is especially convenient if you are planning to use it for different plants in need of different growing conditions. For example, if you want to grow a crop next that requires more shade than the last, you can easily pick up the cold frame and move it to another, more appropriate area.

Cold frames also free up a lot more room in your garden than if you built a whole greenhouse, giving you more available space for other gardening projects. They are much easier to construct, using less but more affordable materials. A corrugated plastic cold frame can be built in just one afternoon using wooden pallets and corrugated plastic. If you are in need of polycarbonate for your cold frame, check out our fantastic range of polycarbonate roofing sheets - you don’t have to look far to get your project started! The wooden pallets can also often be sourced for free with local businesses and garden centres often giving old ones away.

Use Your Cold Frame All Year Round...

Spring/Early Summer – Use your cold frame to harden off seedlings, ideal for vegetables and other young plants that don’t require a full greenhouse but are too tender for rough garden conditions.

Late Spring/Summer – Use your cold frame to create extra heat for your vegetables such as tomatoes, aubergines and chillies to allow a faster ripening time as well as bigger crops.

Autumn – Use your cold frame to protect your young plants from harsher weather, colder temperatures and mild frosts.

Winter – Use your cold frame to protect alpines from rainy weather to stop them from decaying. Your cold frame can also be used for overwintering plants – some can spend their whole lifespan in a cold frame!

Why Use Corrugated Polycarbonate?

Using polycarbonate sheets is a fantastic choice for a variety of reasons. Not only does the corrugated design maximise the strength and durability of your cold frame but it also gives brilliant light transparency, providing up to three times the amount of light that other sheets could. This means that even on greyer days, your corrugated plastic cold frame will still work at its best.

Another great advantage is that because the sheets are corrugated, they naturally provide a little ventilation through the sides of the cold frame. This being said, you will still need to ensure you also prop the lid open on especially sunny days to ensure that your plants don’t overheat. With our cost-effective, affordable range of polycarbonate sheets, you don’t have to worry about spending huge amounts of money to get the results you want in your garden.

How to Build a Cold Frame

Initial Preparation

Building your corrugated plastic cold frame is relatively quick and straightforward, taking only an afternoon’s work. The entire frame can be constructed using wood from a pallet. If you are planning to use an old wood pallet, you’ll first have to dismantle it using a hammer, ensuring you remove the nails. You may also consider treating the wood to prevent rot.

You can accommodate your corrugated plastic cold frame to your garden, making it as long and wide as you like. Just make sure that all of the wood you use for the side panels match equally in length as well as ensuring the wood that you use for the front and the back are equally measured too.

You will need to make the back of the cold frame slightly higher than the front to ensure that rainfall can flow off of the cold frame. This also allows you to maximise the amount of sunlight coming in. Therefore, in this guide we are using four boards at the back and three at the front.

Materials You'll need:

3 boards for the front
4 boards for the back
7 shorter boards for the sides
8 small pieces of wood used to screw the boards together
4 hinges
2 pieces of wood/battons to prop open the lid on very sunny days
Wood screws
Cable ties
1 Vistalux PVC corrugated sheet

Tools You'll Need:

A drill
A screwdriver
Some scissors
A saw

Step-by-step Guide to Building a Cold Frame]

We have broken the building process down into 10 easy steps, so you’ll have your very own corrugated plastic cold frame in no time.

First, lay the three wooden boards that you are using for the front of the frame, horizontally next to each other on the ground. Use one of the smaller pieces of wood to join the planks together by positioning it over the three planks and securing with wood screws. Repeat this further along the planks using another small wood piece to ensure full stability. Make sure you keep the ends of the planks free!
Repeat step one but instead use the four planks to create the back of the frame.
Take one of the seven side panel boards and saw it diagonally in half, creating two triangular pieces.
Then, take three of the wooden side boards as well as one of the triangular side boards and lie them horizontally next to each other on the ground, making sure that the triangular board is on top and sloping down towards the other planks. Secure the panels together using the wood screws.
Repeat step four to construct the opposite side.
Next, use the four hinges to connect the panels together. Screw hinges into place to secure the back panel to each side panel. Add the front panel using the two remaining hinges. Remember - The tallest panel needs to be at the back with the side panels sloping down towards the front!
Now its time to add the corrugated sheet. Cut the plastic sheet so that it matches the size of the frame.
After cutting the corrugated plastic sheet to the appropriate size, rest it on top of the frame. Attach the corrugated sheet to the frame by drilling holes into the top of the back panel on each side as well as drilling into the corrugated sheeting immediately above these holes.
Use cable ties to secure the polycarbonate sheet onto the frame at the back.
Then, tap some nails into the front of the frame and drill holes into the corrugated plastic sheet immediately above where the nails are placed. Add cable ties here, hooking them over the nails to act as a lid and keep it closed.

There you have it, your very own corrugated plastic cold frame ready to start your next exciting garden project!

If you would prefer to follow this guide to building a cold frame in a video, take a look at Nick Bailey’s ‘How to’ video on Gardener’s world.

Some Tips To Help You Get Started!

Make sure you pick the right spots! To properly utilise your cold frame, you should look for an area with appropriate growing conditions for your crops. It is best to start somewhere safe with sunshine and shelter from heavy winds.
Don’t forget to ventilate! With a gardening structure such as this, it is vital to ensure that your cold frame gets enough ventilation, especially in seasons where weather can change so quickly. When you know a day is going to be hot or sunny, prop your frame open so there is no risk of your plants overheating.
Keep it clean! Now this doesn’t mean your cold frame needs to be immaculate, it is in your garden after all! However, it is good to make sure that your corrugated plastic cold frame is not constantly covered in leaves or debris as this can block the sunlight, hindering the growth of your plants. Also make sure that you remove heavy ice in winter as this can cause damage to your cold frame.

We hope you found our how-to guide helpful and that now you’ll give your own corrugated plastic cold frame a go! If you are searching for polycarbonate sheets for your cold frame, look no further. We have a highly affordable selection of high-quality corrugated plastic sheets ready to order.

If you have any other questions or queries, don’t hesitate to get in touch by giving us a call on 01295 565565 or leave us a message in our handy live chat.

If you do create a cold frame from a pallet, take a snap and show us on Facebook.