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The internet and indeed, the Bunnings Workshop website, has plenty of stories of DIY raised garden beds. All of these look really good when they are new but, alas, most of them are made from wood and therefore will deteriorate over time. Of course, for veggies, treated wood is a no-no generally for safety reasons and whilst sealing treated wood with a thick membrane like rubber pond liner material is doable it can be expensive and an extra step in the project that is a nuisance to do.
One solution is to buy steel raised garden bed kits such as the Birdies' range that Bunnings sell. These are very good and I do have one but a DIY version of the same sort of thing is very doable and very economical to build and be long lasting. I have made a few of these and they go together well. Indeed, my construction method involves a lot less work than most DIY versions that I see on the Internet because most of them use timber posts which are often concreted into the ground. Of course, untreated timber posts will not last very long either.
This is what a finished version of my steel raised veggie garden bed looks like next to a Birdies kit raised garden bed...
I have used Colorbond fence sheeting for the sides. Of course, you can use pre-loved sheeting which should make the project quite cheap. I was a bit lucky because, being a regular Bunnings customer, I happened upon a number of sheets of fence sheeting that Bunnings were selling cheap at the back of the store as they sometimes do with 'end of product line' leftovers. These were 2.1m lengths which is not the normal 1.8m lengths that most high Colorbond fences would be made of but which was an ideal length for my purposes. Of course, you can make any length that you want to with your sheets of steel fencing or roofing material.
For the corners, I have used 100mm x 100mm zinc angle. This is thin material that is easily pop riveted to the side sheets and readily available at Bunnings. I bought a couple of 1.8 m lengths for each of my raised garden beds and cut them in half so as to match the width of my sheeting and which also allowed another few centimetres that can be shoved into the ground to anchor the raised garden bed.
Construction is simple enough. The end panels were cut to the desired width with an angle grinder and the corner angles were secured with pop rivets. For ease of construction, I affixed the angles to the sides first using a pallet on saw horses as a work bench...
Carrying the sides with zinc angles affixed at both ends to the eventual spot in the garden where the raised garden bed is to be situated is a lot easier than carrying the fully constructed garden bed, albeit that is doable. In a flat spot, at or near the final installation place, the end panels can be pop rivetted into place ALMOST ready for installation. But wait, there’s more to be done….
The next step is to do something to stop the sides bowing out when filled with soil. This is done by screwing the sides to each other with a few 6mm threaded stainless steel rods cut to length and with washers and nuts on the outside. See the rods and even spacings in the picture below.
Finally, to make the edges safe, very cheaply, I have used 20mm PVC conduit that has been slit down the side with a multitool and slid over the edge of the sheeting, as seen in the pictures above also. That PVC conduit is dirt cheap at around $3.50 for a 4 m length and is to be found in the electrical section at Bunnings.
In terms of filling the high sided raised garden bed, I have used the Hugelkulture method. That is, fill the bottom half of the raised garden bed with hardwood logs and sticks first. These logs will store water more than dirt will. Then I have covered that with layers of home made compost and garden soil.
Does it work? These healthy carrots, grown in the same bed as pictured above, tell the story.
Tools used: Angle grinder to cut the panels, angles and stainless steel rods to size, multi-tool to slice the PVC conduit, electric drill to drill holes for the pop rivets, pop riveter.* Spirit level for the final installation.
[*. I will confess to cheating a bit in relation to the pop riveter. I started the job using a manual pop riveter but found that for my ancient arthritic hands, that was a bit slow and hard to do because I did use some fairly large pop rivets. Then, when I mentioned this to a mate, he gave me his old pneumatic pop riveter that he had no further use for. When I married that to my cute little hand-held air compressor as shown below, the pop riveting became dead easy and, frankly, good fun.]
In closing, I hasten to mention that none of the above construction method was my invention, Rather, I have found inspiration from various suggestions on the Internet and Youtube and have adapted them to the materials that I have found in Bunnings.
I have made several of these steel raised garden beds and of different sizes to suit the available spaces in my back yard. Here is my smallest - a squarish one.
Many thanks for sharing this raised garden bed project with us @Claudeduck. It is so useful to have a step-by-step instructions and so many helpful construction tips. Your carrots are thriving! As you point out, the best thing about this construction method is that you can adapt it to suit the size of the available space in your garden. I can't wait to see your next project!
Jane
Thanks.
They were very fine carrots too...
Not only tasty but easy to peel because they were very thick. The cook in our house loved them. [The cook in our house is not me! In a cooking class, I would be in that half of the class that makes the top half possible. :). ]
This was the first of several raised garden beds of this style that I have built. This one was built in late 2019 and it has since produced excellent crops of carrots, sweet potatoes, cucumbers and there is now a crop of dwarf bush beans finishing up as summer draws to a close. When that crop finishes, it will be time to top up the soil and compost in the raised garden bed ready for the next crop of I-am-not-sure-what yet.
Of course, the benefit of high raised garden beds of the sort shown here is that they are easy to tend to by old dudes and dudettes who might have sore backs and cranky knees. 
Hi @Claudeduck,
That's a wonderful way to construct a raised garden bed. You've put a great deal of thought into its construction, and that has really paid off with the final unit. Brilliant thinking to add the threaded rod to stop the sides bowing out.
Thanks for sharing and I look forward to your next project.
Well done.
Mitchell
