How to Build Corrugated Metal Raised Garden Beds

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One of my favorite parts of being a woodworker, aside from bringing in a five-figure income, is that I can take on projects around the house to improve our lives. When we moved to our new home last year, we realized that our backyard in Central Oregon had great southern exposure that would be perfect for growing our own vegetables. After the previous four years on a property surrounded by huge fir trees, we were stoked to set up a real garden again.

After a few months of research, I decided on building cedar and corrugated metal raised garden beds on one side of the house. I love this design because they help keep costs down by using less wood, they sit at 25″ tall, which means no bending over the garden to weed or tend to vegetables, and they are deep enough to handle even the longest carrot varieties we can throw at them.

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    Building Your Own Corrugated Metal Raised Garden Beds

    Building your own metal raised garden beds is a super easy process that can easily transform your garden space in a matter of hours. We love these planters as they can easily be scaled up or down in size and height to match any space’s needs.

    It may seem daunting at first to cut the corrugated metal (I was a bit nervous too!), but with a decent pair of tin snips, you can quickly cut the metal down to size.

    If you’d like a detailed set of instructions and measurements, we have plans for purchase at our Etsy shop.

    Materials Needed to Build Metal Raised Garden Beds

    You will only need a few materials to build these planter boxes, and during normal times you can build a 4′ x 4′ box for right around $100.

    Cedar Lumber

    I built our metal planter boxes out of cedar but you can also use redwood, juniper, or even treated lumber. Any rot-resistant wood will work although we personally like to stay away from treated lumber in our planter boxes.

    You’ll need the following pieces of lumber to get started:

    • 1 – 4″ x 4″ x 96″ cedar
    • 4 – 2″ x 4″ x 96″ cedar
    • 2 – 2″ x 6″ x 96″ cedar

    Galvanized Metal Roofing

    Galvanized metal roofing sections can be found at most any big box hardware store and they only cost around $15 per sheet. These corrugated metal sheets come in a standard size of 8′ long by 25″ wide.

    These planter boxes use two sheets per box, although if you halved the height, you could get away with one sheet for the entire box.

    Wood and Sheet Metal Screws

    I used both 2 1/2″ Kreg screws and 3″ wood screws to build the wood frame and 1″ roofing screws to attach the corrugated metal to the frame.

    Tools Needed to Build Galvanized Raised Garden Beds

    You will only need a few tools to build your own raised garden beds. I used a miter saw for cutting the wood down to size (although you can easily just use a circular saw and speed square), a pocket hole jig for the joinery, and a cordless drill. That is it!

    If you choose not to go with mitered corners on the top of the planter box, you could even get away with having the material cut for you at the hardware store.

    How to Build A Metal Raised Garden Bed

    Here is a walkthrough of how I built these raised garden beds. Once again, if you’d like more detailed plans, they are available in our Etsy shop.

    These planters’ overall dimensions are 4′ x 4′ x 25″ tall. The interior planting dimensions are approximately 40″ x 40″ x 23″. This amounts to the planters holding approximately 21 cubic feet of soil.

    That means it would take around 10 of those 2cf bags of soil you can buy at the nursery or, if you buy by the yard from a dump truck, then you’ll have a little leftover.

    Break Down the Lumber

    Cutting Cedar for metal raised garden bed

    The first step is breaking down all of the lumber. The 4″x4″ cedar boards are cut into four equal 24-inch sections. Each of the 2″x4″ cedar boards are cut down to 40″ sections. You should end up with eight total 40″ 2″x4″ boards.

    The 2″x6″s will be cut with 45 degree miters at a length on the longest edges of 48″.

    Drill Pocket Holes in the 2″x4″s

    Drilling pocket holes in the raised garden bed lumber

    Next up are the pocket holes. I added two pocketholes to the each end of the 40″ 2″x4″s. These pocketholes will face the inside of the planter and eventually be covered up by the corrugated metal so they will be totally hidden on the finished planter.

    Just set the depth stop on the drill bit to 1 1/2″ and raise up your drill guide so you don’t end up drilling through the bottom of your board and the bottom of the Kreg jig. I have made that mistake more than once!

    Put the Frame Together

    Building the metal raised garden bed frame

    Next up is attaching the 2″x4″s to the 4″x4″ posts. Line up two 2″x4″s with the top and bottom of two 4″x4″ posts. I did this on a flat surface with scrap pieces of 2″x4″ underneath the 2″x4″s. This left the edge of the board about 1/2″ below the edge of the 4″x4″ post. This 1/2″ will come in handy when installing the corrugated metal as it will allow some separation at the corners.

    Attached the boards using the 2 1/2″ Kreg screws. It helps to butt the edge of the 4″x4″ up against a wall or other object to keep the faces pushed together while you drive in the screws.

    Repeat these steps until you have two sections that look like the picture below.

    Layout of the corrugated metal raised garden bed frame

    From there you can stand the sections on edge and attach the 2″x4″s to complete the frame. Be careful moving the frame at this stage as the joints aren’t very strong yet. Once you add the top sections and metal the planter will be totally solid.

    The picture below is what you’ll end up with once all the frames have been attached. Note that there is no bottom or top so you can orient it whichever way looks best before proceeding on to the next step.

    Corrugated metal raised garden frame

    Attach the Top

    Adding the top frame to the raised garden bed

    Line up the 2″x6″s so that you have approximately 1/2″ overhang around all the edges. My miters never seem to line up perfectly, but I don’t worry about it too much since this is just a planter box.

    Drive four 3-inch wood screws through the 2″x6″s into the top of each 4″x4″ post and another three screws along each of the top rails. This will provide plenty of stability to where you’ll be able to sit on these boards while you’re gardening without worrying about them rocking.

    Attached the Corrugated Metal

    Adding corrugated metal to the raised garden bed

    Cut the metal down to a length of 40 inches. I do this by marking the metal with a permanent marker every few inches then cutting along the lines with tin snips. Lift the metal offcut as you go to keep the snips clear and tracking along a straight line.

    At this point, you can also cut off the bottom 1 1/2 or so inches of the metal if you wish. These sheets come in 25-inch widths, and our planters are only 24″ tall. You can also do as I did and fold the excess over as this will be at the bottom of the planter anyways.

    From there, place the corrugated metal inside the planter frame and screw it to the frames using the 1-inch roofing screws. I placed 5 screws along the top and bottom.

    You may notice some flex in the metal if you push in the center along the edges, but this is hardly noticeable once the planters are filled with soil.

    If you wanted to add a little extra stability, you could always add some extra vertical supports between the 2″x4″s. In fact, if you’re building planters longer than 4 feet, you will want to add extra vertical supports, at least in the center of the planter box.

    Finally, you can either leave the wood natural or add an exterior wood finish.

    Installing the Planter Boxes

    Now it is just a matter of placing the planter boxes in their final location. Because of the metal sides these boxes are surprisingly light and easy to move around.

    You can add chicken wire or other mesh to the bottom to keep burrowing animals out of your vegetable garden. It is also a good idea to line the interior of the box with landscaping cloth to help contain the soil and better protect the wood and metal.

    Questions About These Planter Boxes

    Here are a few questions folks have asked about this planter box design.

    Does the metal get hot in the sun?

    The metal surface ends up reflecting most of the sun’s heat and, while it does get warm, it doesn’t get overly hot to the touch and won’t result in your soil overheating.

    Is galvanized metal safe for the garden?

    Galvanized metal is coated in a layer of zinc which has been bonded to the steel. Heating the steel to almost 400 degrees or exposing it to highly acidic materials can cause this bond to break down, but this should not be the case in your garden. If you decide to cut these metal sheets with a torch or plasma cutter, use extreme caution as these processes can give off extremely harmful gasses.

    Final Thoughts on Building Your Own Metal Raised Garden Beds

    These raised garden beds are an easy project to build for your own garden or sell locally. Many gardeners are looking forward to the growing season in the spring and are willing to pay top dollar for planter boxes like these. They are easy to load up on a truck or trailer and install in a client’s garden with their lightweight.

    You can take a look at our plans here if you want a more detailed set of instructions for building your own planter boxes.

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