How to Make a Cold Frame Step-by-Step

Cold frames are a vital component in the gardener’s toolkit. Use them to start off seedlings earlier in spring, to keep growing crops into winter, or to help harden off tender plants such as chiles in early summer. Read on or watch our video to discover just how easy it is to make your own…

How to Make a Cold Frame Step by Step

Cold frames really are the gardener’s best friend! If you don’t want to splash out lots of money buying one, don’t!  They are simple structures that are easy to make at home with basic tools and second-hand materials. Old windows make perfect lids, while it’s simple to construct a box frame from wood. 

Cold Frame Materials

Start by sourcing your lid. A salvaged window or windows is the usual choice, but a clear door such as a shower door will also work well. You’ll also need some strong hinges to fix the lid to the wooden frame.

Source some lengths of pressure treated lumber and cut them to match the dimensions of your lid or lids. In our project we’re using three boards at the front, then four at the back. Making a slope like this will let in the maximum amount of sunlight. Seven shorter boards are used for the frame’s sides. The seventh length is cut in half diagonally to give two identical triangular boards – one for each side, to match the slope

All of the boards will need to be screwed to four corner posts. To prop open the lids on sunny days you’ll also need two battens, one short and one longer.

To put the frame together you will need some wood screws, a drill and a screwdriver.

How to Build a Cold Frame

1. Screw the side boards onto their corner posts.[AH2]  Use two screws at both ends of each board. You will find it easier to drill pilot holes before screwing the boards into place.
2. Screw the narrow end of the triangular top boards down into the board below.
3. Screw the front and back boards to their corner posts.
4. Carefully position the lids onto the frame so the lid and frame are flush at the back.
5. Screw on your hinges. Longer lids may need several hinges along their length.
6. Screw the lid supports into place on the inside of the frame. The short one should go on the front of the frame, and the longer one on the side. They screwed on just loosely enough to enable you to swivel them up to prop open the window.
7. You can also screw some handles on the front ends of the lids if necessary.

How to Use a Cold Frame

Cold frames can be placed directly on the soil, or on concrete or slabs.  Use them to grow salads throughout winter, start off tender crops, or to help harden off indoor-sown plants before they’re planted out.

Do you have the Almanac Garden Planner? With your Garden Planner, it’s easy to add a cold frame to your plan, and it will automatically extend your season for crops grown beneath it. Try the Garden Planner for free with our 7-day trial here.