DIY Garden Cloche – Mini greenhouse – Cold frame

How to Build a Garden Cold Frame With Recycled Windows

Cold frames are the ideal solution for early or late season gardening if you live in colder climates. They are also fantastic for seed germination.

Once the framework for the raised beds with storage benches was complete, we began building the garden cold frame.

We wanted to keep the raised beds as modular and standard as possible, so we built them to a standard 2’ x 4’ size. Then I found salvaged windows to cover the raised bed and turn it into a cold frame mini greenhouse.

If I could do it again, I would have selected the salvaged windows first, then built the raised bed to match the window dimensions. Luckily, I was still able to find windows to make it work.

What is a Cold Frame?

A cold frame is essentially a mini-greenhouse for a raised garden bed. It is a transparent-roofed enclosure that is used to protect plants and seeds from adverse weather.

What is the Difference Between a Cold Frame and a Greenhouse?

Historically, cold frames were used in addition to heated greenhouses.

The biggest difference between the two is that a cold frame only stands a few feet tall and doesn’t use a heat source or ventilation, unlike a greenhouse does for a year-long controllable plant growing climate.

Where Should I Put a Cold Frame?

The best place to build a cold frame is somewhere sunny yet sheltered, so plants and seedlings can get as much light and warmth as possible while still being protected by the elements.

I built our cold frame in the back corner of our garden against the fence. This gives it as much protection from the elements as possible, while still receiving sun during the day.

When Should I Use a Cold Frame?

The best time to use a cold frame is in the spring/early summer and the fall/early winter.

In the spring and early summer, cold frames, cloches, and mini-greenhouses are useful when hardening young plants and seedlings, or getting a jump start on seeds. In the fall and early winter, a cold frame can be used to protect hearty fall crops and plants.

In the summer when the weather is too hot to keep the cold frame closed, use it as a regular garden planter.

Can a Cold Frame Be Used For Seed Germination?

Absolutely! In fact, you can start your seeds in a cold frame up to six weeks earlier than you would typically plant them in the ground!

What Can You Grow in a Cold Fame?

Apart from starting seeds and seedlings in early spring, there are many different planting options for a cold frame.

Spinach, chard, arugula, and a variety of other lettuces are great options for a cold frame in early spring or fall. Radishes, leeks, and carrots also do well in a cold frame in the early and late seasons.

Using a cold frame is a great way to get into winter gardening, especially if you don’t have space for a full greenhouse.

Does a Cold Frame Need to be Airtight?

Not exactly, there can be small air gaps to help with ventilation and circulation.

However, when the weather gets really cold (especially at night), you should try to make your cold frame as air-tight as possible. You can do this by filling in air gaps or covering your cold frame with a blanket to protect it from the elements like snow and frost.

How To Make a Cheap Cold Frame, Cloche or Mini Greenhouse

There are many ways to make a cheap cold frame.

Kits are available online for cloches and mini-greenhouses. You can even use plastic or glass containers and bottles to protect young garden seedlings.

My favorite way to make an inexpensive cold frame is by using salvaged windows!

How To Make a DIY Cold Frame From Salvaged Windows

First, find a local architectural salvage yard or antique shop. Often, recycling centers like resource will also carry old windows and glass doors.

I went to Queen City Architectural Salvage in Denver for my salvaged windows.

Note: When wandering around architectural salvage yards and antique shops, you’ll always find cool things to look through, and the possibilities for cheap DIY projects and rehabs are endless.

How Big Should A Cold Frame Be?

This is really up to you, and how much space you have to work with.

I would recommend a minimum of 2’ x 2’ however you can make your cold frame as small or as large as you like.

My only recommendation is to find your salvaged window(s) or glass door(s) first, before building the raised bed.

Cold Frame Window Size

I decided to go with two 2’ x 2’ salvaged window panes for my 2’ x 4’ raised garden bed.

I liked the option to close half of the cold frame and adjust the window openings depending on the heat of the day.

I also liked that one of the windows was transparent and the other was frosted, so I could control the light distribution for different plants.

After selecting the window(s) or glass door(s), they will likely need a little TLC.

The windows I purchased were old and had been living outside, exposed to the elements for who knows how long.

How To Refinish a Window or Door

Wash the glass to remove dirt and grime.

Then begin sanding down and stripping away any existing paint or stain. You may need to use a paint scraper to remove more difficult paint sections, especially if the glass is painted.

The existing paint or stain does not need to be removed entirely, but you want to remove as much as possible to create a clean rough surface to work with.

Next, use a tacky cloth to remove any dust that could make the paint appear bumpy or uneven.

Tape off the glass with painter’s tape on both sides of the window or door.

Select an outdoor paint for the windows or door. I went with classic white paint. Then apply two coats of exterior paint to the wood trim.

Note: You may need to prime your windows or door before painting.

Cover the window or door frame with several light layers of paint. It’s better to do several light coats of paint than one heavy coat. Let each coat dry before applying the next coat.

Another option is to do several light coats of spray paint. If using spray paint, Cover the entire glass pane with paper, tape, or a tarp to prevent paint from getting on the glass.

For more durability, apply a clear layer of liquid or spray sealant.

Once the paint has dried, add new hardware to act as the cold frame handle.

I purchased these handles and some hinges off amazon.

All done! The salvaged window(s) or door is ready to be installed on your cold frame raised bed!

How to Build A Cold Frame Raised Garden Bed

Read my post on how to build raised garden beds with storage benches to learn how to build the base for this Cold Frame Planter.

You will need 2×4 lumber for the ledges and hinges to attach the cold frame recycled window lid.

Build the back wall of the planter taller than the front of the raised bed to create a slope for the window lid to sit on.

Attach a 2 x 4 piece of lumber to the back wall of the cold frame using wood screws. This will create a ledge for the window or door hinge to rest on.

Add another 2 x 4 piece of lumber to the front wall of the raised bed to create a ledge for the window lid to rest on when closed.

Attaching Windows or Door to a Raised Bed

Attach one side of the hinge to the Recycled window or door first.

Then attach the other side of the hinge to the back ledge of the raised bed. Check that the window or door is straight using a level.

Note: Do not fully screw the hinge screws into the ledge until the window is in the correct spot. This allows for adjustments as needed when installing the windows or door.

Once the window or door is in the correct location, finish screwing the hinges to firmly attach the window or door to the back-wall ledge. Test the window(s) or door by opening and closing it to make sure it does not catch on anything.

I waited to add the side of the raised bed until after the windows were installed. This was done intentionally to make sure the lumber would align with the underside of the window when closed.

With a pencil, mark where the lumber needs to be cut in order to align with the closed window lid and make it as air-tight as possible.

Using a jigsaw or table saw, carefully cut along the pencil line to create an angled piece of lumber that will cap the end of the cold frame and seal it closed.

Finally, screw the side piece to the support posts of the planter using wood screws.

You can add additional support posts to keep your cold frame window(s) or door open at differing heights when the weather is warm.

I decided to attach large carabiners to eye hooks on the back fence to keep the cold frame lid open and secure.

That’s It! Enjoy the New Cold Frame!

Want to Learn More?

Check out my blog post to learn how to build these raised garden beds with storage benches, and subscribe to the Bonus Space to stay in the loop for future posts like this one.

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If you have any questions, or a helpful tip or two of your own that you would like to share about building your own cold frame or raised garden beds, leave a comment below or send me an email! (Yep! I’m a real attainable person who cares about your project’s success as much as my own!)

Cheers!

Mel