Corten Steel Planters – top things to consider before buying
Corten steel planters I fabricated in the front landscape of a client’s home in California
Corten steel planters are beautiful. Plus, they are designed to last outdoors for decades with no maintenance. I love this material. The rust patina that develops on its surface is beautiful and ever changing. Over time and seasons, it’s hues and surface patterns will continue to evolve. A very meditative process to observe. And, if your planter was fabricated using quality materials and solid craftsmanship it will become a timeless sentinel in your landscape design.
You may or may not already know that corten steel, also known as weathering steel, is significantly more expensive than the standard mild steel that you see rusting away all over the place. There is good reason for this. For one, corten steel should last 8 times as long as mild steel. Meaning, mild steel will be rusted through and in the garbage heap decades before corten steel.
Corten is derived from the 2 key aspects for it’s creation: corrosion resistance and tensile strength. So, it lasts forever and it’s super strong. Exactly what you want for a planter that will be filled with soil, growing roots, rain, ice, etc.
Now, I’d like to get into the details that you should be aware of / ask about when you speak with your corten steel planters fabricator / supplier.
Corten steel planter beds I fabricated in the landscape of a client’s home in Washington state
Material thickness / gauge
It’s important to know the gauge of corten steel your planter will be made from. Gauge is a whole number that identifies the thickness of the corten steel. As the gauge increases, the material thickness decreases. So, 14 gauge is heavier / thicker than 16 gauge. The thicker the material the heavier it is and the more expensive it is. Steel is often priced as $ / LF (linear foot). When researching or shopping for corten steel planters make sure you are comparing apples to apples. I use either 14 or 11 gauge corten steel to fabricate my custom corten planters.
Welded seams
For outdoor welded planters, you don’t need to have fully welded seams, as long as the fit up is nice and tight. As long as you have good strong stich welds every few inches it will be fine. It introduces less heat to the steel thus avoiding potential warpage and weak spots. If however, you will use your corten welded planter indoors you will want a water tight container and in that case will need fully welded seams. You’ll also need to make sure to communicate that you don’t want drainage holes in the bottom. (This is ONLY if you’ll keep it indoors)
Drain holes
I add 1” diameter drain holes uniformly spaced along the bottom of all my welded planters. I wouldn’t go much smaller than that to minimize clogging. Also, install a weed barrier / mesh liner on the bottom of your planter prior to any drainage rocks and soil. This will minimize the chance of soil running out the drain holes with heavy rain, etc.
Top edge bend / Lip
When steel is bent it becomes stronger. So, when I add a 90 degree top lip / edge bend to my corten steel planters I am adding both strength and an aesthetic aspect. Often, I will add what is known as a return on the top edge as well. This is another 90-degree bend on the inside of the top edge that goes down towards the bottom. More strength and aesthetic refinement.
Size
Most of the corten steel planters available in the market today are quite small. A big reason is to minimize production costs. Sure, there are applications where your project can only accommodate a small corten steel planter box. These should be the exception rather than the rule. Just like any material used for a planter box, corten steel will heat up in the hot summer sun. Whether plastic, wood, concrete or corten steel a planter will get very hot and will undoubtedly dry out the interior soil to some degree. When the interior soil volume is small compared to the surface area of the planter box it will dry out quicker. In addition, the closer that roots are to the edge of the planter the quicker they can dry out and be permanently damaged.
Corten steel planters on Orcas Island, WA
