By BDo & Bean
This Cats and Catts instructional essay discusses how to build a multi-use cold frame. You can use it for specific cold-tolerant orchids, and a cold frame can extend the time some of your orchids can stay outdoors. Cold frames can become an integral part of vegetable gardening or, you can do what I’m going to do, and use it to germinate daylily seedlings.
There are plenty of cold frames kits for sale online and plenty of internet advice about how to build one, but I promise you that my Insane Cold Frame design is the best.
The reason that this is the Best Cold Frame Design Ever is because I designed it with Selena Sabine by my side and her tail whacked at my hand as I sketched the diagram, thus inserting the proper degree of torque and resistance into the design plan. I drafted it on the back of an envelope for an added element of professionalism.
The other great thing about the Insane Cold Frame is that you can build it with minimal sawing as long as you take all of your measurements ahead of time, walk into Home Depot with a plan, and have them saw your wood for you free of charge. If you take advantage of this service, you lose some control over the building process, but you can save time, avoid the shame of making miscalculations at home, and everything will easily fit in the car without bungee cords or back injury.
Step 1: Find the Sash
You need to design around the window top, or what horticultural types call the “sash.” Don’t do anything or buy any supplies until you have the glass sash. You might find something appropriate at a garage sale or thrift store. Or you can do all of your shopping at Home Depot. The important thing is to take a careful measurement of the dimensions of the window frame. You need to know the length and width of the wood or aluminum frame -- not the dimensions of the glass. Those two numbers are important, so take multiple measurements just to be careful.
Step 2: Make a Shopping List
Ideally, your cold frame will face South and will maximize the space running West to East. Therefore, it’s going to be wider in the front compared to the sides.
You’re trying to build a wood frame that will fight snugly around the sash, so add ½ inch to the width and length measurements of the window frame (I forget my exact mathematical reasoning for adding a ½ inch, but it worked out). This will give you a small number (the width of the glass frame as it will run along the side of the cold frame plus ½ inch) and a big number (the length of the front and back of the wood or aluminum frame plus ½ inch).
Here’s what you need:
* One piece of WeatherShield 2 in. x 4 in. x 7 foot Prime Pressure Treated Lumber.
* Several pieces of WeatherShield 2 in. x 6 in. x 8 foot Prime Pressure Treated Lumber. I pulled about six boards, but I think the guy only needed to use four for my 33” x 35” frame.
* Two skinny pieces of 1 in. x 2 in. boards, enough to run across the front (that may or may not be sold in the same section as the other lumber).
* You’ll also need a box of 3” or 3 1/2” screws, a box of 1” deck screws, a cabinet handle, two heavy-duty hinges, and paint.
Step 3: Shopping
Find one of those over-sized steel grocery cart contraptions, preferably one with a broken wheel. Roll over to the WeatherShield lumber.
My Home Depot strategy relies on the kindness of strangers instead of math. You’ll want a specified number of 2x4s and 1x2s, but the number of 2x6s depends upon the size of the glass frame. You don’t have to be precise – just get more than you think you need and load them on the metal cart.
Sidebar: Have you ever bought lumber from Home Depot? I think it’s like buying yogurt – you might want to reach back beyond the first few rows to get the freshest product. The wood that previous customers have rejected as too twisty or John Merrick-like often remains in the front of the stack. If you want to look like you know what you’re doing and, perhaps, avoid buying bum lumber, set it at a diagonal and stare down its length. Do you see any weirdness on that flat plane? Then, set the board down on the concrete. Does it lay flat? A good Home Depot employee will help you inspect the boards and will be honest in rejecting the ones that are lousy. A bad Home Depot employee will try to rush you by grabbing the first board he sees and will try to put it in your cart before you have a chance to detect its faults. I’ve experienced both, with the former outnumbering the latter.
Step 4: Requesting the Cuts
The Home Depot team is often busy helping other customers. It would seem that risking permanent injury cutting other people’s lumber would be a highlight of their work experience, but maybe I’m wrong. Anyway, if it’s a busy Saturday and you find yourself being ignored try this approach: Walk over to the wood cutting station with a small piece of wood in your left arm (there should be some scraps lying around near the station) and place it near the blade. Take your right arm and stretch it in the direction of the control panel. Someone will assist you shortly.
Now that you have their attention, tell the lumber cutter that you want the 2x6 boards cut into five pieces of x-inches [the small number, the sides) and five pieces cut to x inches [the big number, the front and back]. The guy might say “With as many boards as it takes to make five of each length?” You should mutter something like “Yeah.” (See? No math!). Next, before he leaves, tell the dude to cut the 2x4 into two 12” pieces (the front posts) and two 18” pieces (the back posts). As a final request, take one of the short, recently cut, pieces of 2x6 and tell the dude to cut it at a diagonal. This will produce two triangles with a 6” back that will align with the back of the cold frame. The hypotenuse of both triangles will create the downward slope on the cold frame, maximizing sun exposure. You could have your lumber-cutting friend cut the 1x2s in half if you want easy transportation in a car. Those pieces will be cut to spec toward the end of the assembly.
Step 5: Paint
Prime all of the pieces, including the wood or aluminum on the window frame. I used Kliz 2 Latex. Two coats are better than one, but wait until the first one dries.
Step 6: Assembly
Here’s what I think you should do (not necessarily what I did). I would lay out and stack up the lumber so you can visually understand what you’re trying to do. Then, I would create a big wood box by screwing the 2x4 posts into the side pieces (the short 2x6 pieces). Then I would screw in the front and back. You’ll want the longest piece of the 2x4 for all four posts facing the front of the cold frame. The top of the front posts should be flush with the top of the box. The back posts should extend to allow the final long piece in the back.
It should be obvious where to place the two triangular pieces. I pre-drilled two holes in each piece of triangle wood and carefully screwed them into place.
Step 7: Paint Again
Step 8: Hinge the Sash
Use 1 ½ ” screws to attach the two hinges to the window frame and the back of your cold frame structure. The little scroll thing on the hinge should face inward.
Step 9: Finishing
You’ll use three pieces of 1x2s to hold the window in place. These pieces will be screwed into the top of the frame and will run in front of the window and along the sides. You’ll be setting the wood “tall,” so that its narrowest side abuts frame. Therefore, it’s especially important to pre-drill holes before you drill in the screws, otherwise the skinny lumber will split. I went light on the screw action and only used two per board. The seal doesn’t have to be perfect, and cold frames need ventilation. Foam weather-stripping offers a nice and inconspicuous way to seal corners that need to be sealed.
I screwed the handle into the middle of a 1’ piece of 1x2. Then, I attached it to the window using multiple screws, pre-drilling all the way.
That’s my Insane Cold Frame plan and, despite my vast reservoir of inexperience doing things like this, I think it turned out well. Although Bean and I designed it, and I did all of the labor (expect for the Home Depot wood cutting step), I can’t take all the credit. I need to warmly acknowledge the carpentry and woodworking mentorship of Crazy Eyes Jonny, Rockin’ Randy Mac, and KDo. All of the flaws in the design and execution, however, are solely the fault of Selena Sabine.