Building a cold frame

If you find this useful, download the latest version of our pdf guide HERE. Or read through the page below. Where, at the the foot of this page I have added useful links for further reading.

The Wrigglers will update this page as they discover more top tips …

making a cold frame guide. This page shows the before and after. Wood on a bench and a cold frame, built and sitting in a raised bed
cold frame

The Wrigglers are Amateur Gardeners. This is our guide to making a cold frame. I looked at the cold frames for sale and liked the look of the ones with wooden sides. Quite expensive to buy, cheap to build.

Why build a cold frame?

Cold frames protect plants from strong winds and retain heat. Cold frames extend our gardening season, both in the autumn to protect plants for a few more weeks and in the spring to get a jumpstart on sowing seeds.

download a pdf of this guide

Where to start?

Figure out where you want it to go, then measure up the width and depth. My example is 700*500mm. Next I mocked up the lid and frames to calculate the wood needed. I made this with:

  • 5x Feather Edge Fence Board – 150 x 11mm x 1.8m
  • 4x Treated Sawn Timber – 19 x 32 x 2400mm
  • Back Flap Hinge – 38mm Pack of 2
  • 1x Treated Sawn Timber – 50 x 25 x 2400mm
  • 3mm Solid Polycarbonate Clear Sheet 1000 x 500mm

You could use recycled glass or plastic for the lid

download a pdf of this guide

making the frames for a cold frame

Making the frame

I made each of the sides, screwing them together, checking the diagonals to make sure they were square. Pretty solid, but once screwed together as a unit they will be made super-solid by the feather edge board.

For the lid I made half lap joints to ensure a bit more rigidity. This too will be made more solid once the plastic is screwed on.

download a pdf of this guide

Putting the ‘whole’ frame together

Once you do this, check the diagonals to make sure the frame is square. Then screw on the wooden sides, shiplap or feather board. Do this before attaching the lid.

download a pdf of this guide

showing the frame parts of a cold frame being put together
A diagram Showing the frame parts of a cold frame being put together
Attaching the wooden sides to the frame of the cold frame

Measure, cut and build up the feather board sides

I started at the base of the cold frame. Completing a whole layer before building towards the top. In my original calculations I left 30mm in the measurements as an overlap. I don’t know if this is correct, it just felt right!

FYI – because the board ‘feathers’ so will each cut, if you want to make it look neat and tidy.

Once completed, set it down and attach the lid – be aware because the lid is on a downward angle the hinges will need cutting in or, as I did, attaching on the rear of the box.

download a pdf of this guide

Attach the lid and glass/plastic

I laid the plastic sheet on top, screwed it onto the frame through batons laid over the top.

To hold the lid open I cut and notched a leftover piece of wood. As you can see:)

You can download a pdf of this guide if useful here

A diagram Showing the lid of the frame being glazed

For an expert’s eye on pruning:

RHS Pruning groups

Understand the groups and you understand when, how and which plants to prune.

These groups are designed to offer gardeners a general guide on how to prune a tree, shrub or climber.

LINK


Pruning is one of those grey areas for me. The info here is not only fun to read, but will save some of my plants from an overly keen secateur-wielding gardener, like me.

Simon Haynes


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Can worms prune? Yes they can!