The short answer is yes, they are absolutely safe for gardening use. Since it requires acidity to break down the zinc coating that galvanized steel has, and most garden soils are neutral, it has little effect. In addition, zinc is an essential plant micronutrient and a normal part of soil. We'll go into more detail about all of this later!
We love metal loft beds so much that they were the first product we chose to open our online store. With a variety of options, we think you'll love these high-quality galvanized garden beds.
Galvanizing is the process of bonding a layer of zinc to the surface of steel or other ferrous metals such as iron. This process prevents steel or iron from rusting when in contact with moisture.
Most galvanized steel is made using a hot dip process. The steel sheet, whether corrugated or smooth, will be completely immersed in molten zinc. This creates an even coating on the steel surface. Sometimes the metal is cooled to allow the material to fully bond and then re-dipped in a secondary coating.
Not all galvanized steel is coated with pure zinc. Some galvanized metals are heat treated with alloys. For example, Aluzinc is an aluminum and zinc coating commonly used for hot dip galvanizing. Aluminum forms an outer layer that protects the zinc and steel inner layers from moisture damage.
What is galvanized steel used for?
A better question is what galvanized steel is not used for. Galvanized steel is the material of choice for livestock watering troughs, granary and water storage container exteriors, shed construction, roofing, gutters and downspouts, and many other products. It is sometimes used as a durable fencing board.
Galvanized steel pipe has also been the standard for home plumbing for decades. While it is no longer the case that galvanized pipes have been replaced by PVC and copper, most older homes still use galvanized fittings. These pipes will continue to last for years as long as the zinc coating remains intact.
In food use, galvanized metal is less common in cooking and more common in storage containers. When zinc is heated to high temperatures, it can emit gas into food and the surrounding air. This makes it unwise to use in cooking vessels. However, containers made of galvanized steel are great for storage!
Does galvanized metal leach zinc?
yes and no. If you have extremely acidic water, such as acidified water from a well that has not been treated to neutralize pH, zinc will gradually break down. If the coating is thick, the process can take decades. Most municipal water sources neutralize the pH of the water through their facilities, which means it's unlikely to be a major problem.
In fact, zinc is a normal component in most soils. Both plants and humans need small amounts of zinc to survive. You can also find it in your daily multivitamin! Plants need less zinc than we do, but it's still a necessity. The tiny amounts they may be absorbing from your bed won't damage any food you're growing, nor will it be harmful to the plants themselves.
Zinc itself may not pose a threat to human or plant health, but impurities in zinc may. Concerns have been raised about lead contamination in zinc. This has led manufacturers to take steps to use only pure zinc or aluminum-zinc alloys to reduce the risk of lead contamination. Lead in galvanized containers is less likely to be a problem than lead found naturally in soil.
So yes, acidic conditions may cause some zinc leaching. But this will be minimal, and some plants may actually prefer a slight zinc level in the soil. As long as the steel comes from a reliable manufacturer, there is no need to worry about your bed leaching toxic substances.
Will galvanized metal leach aluminum?
While one can never say never, aluminized zinc does not present a significant risk of aluminum leaching into the environment. The aluminum used for galvalume is lighter than zinc when melted and floats to the outer surface during hot dipping, providing an ultra-thin protective coating to the zinc. This protective coating prevents the more soluble zinc from leaching out, and it even adds another layer of protection to the aluminum surface if there is any additional coating (like paint).
Aluminum itself is not as soluble as zinc, which is why it is used so consistently in food storage. In addition, it is resistant to acidic conditions, which is an important consideration when pairing with the more soluble zinc. We wouldn't have most of the long-term food storage options we currently have if it weren't for aluminum liners in canned food and aluminum beverage cans! There were concerns about the safety of aluminum cookware as early as the 1960s and 1970s, but thorough research has determined that even this poses no risk to humans. Since your garden bed will never reach the hundreds of degrees of heat your cooker generates, even in direct sunlight, the very limited amount of aluminum in a galvanized coating is very safe to protect the zinc from degradation.
Can galvanized steel be used for loft beds?
Absolutely! Galvanized metal raised beds are becoming some of the most popular garden beds. They are durable, strong, damage-resistant, won't rot like wood, and will last for decades. Plus, they look great and can evoke a ranch or industrial vibe. A galvanized planter won't expand or shrink, doesn't require oiling or painting to maintain it (though you certainly can if you want to), and will take whatever nature throws at it.
Shallow raised beds are easily filled with your preferred pH-neutral, well-drained soil. However, deeper beds may require more packing material. We have a great article on how to fill tall metal garden beds that digs deeper into the subject!
Are metal raised garden beds too hot?
Not at all! It is true that most metals heat up in the sun. But moist soil is a magic coolant for hot metal. As a general rule, your vegetable garden or pots won't get too hot, especially if you've been watering them.
Because the metal can conduct some heat, the soil clinging to the sides of the raised bed may be warmer than the center of the bed. This is actually a beneficial thing, especially in the spring. The soil in a raised bed heats up faster than the ground, allowing you to start a vegetable garden sooner. Your seedlings will appreciate the warm soil at their roots!
In mild climates, metal raised garden beds can help you maintain a more consistent soil temperature throughout the year, provide good excess water drainage, and more. A hard, sturdy material will make a good cold frame base for your overwintering plants. These beds hold moisture well when using a soaker hose.
Raised Garden Bed Options
Choosing a commercially made galvanized garden bed can be complicated. There are a surprising number of options on the market, from large vegetable garden styles to basic planters.
I am very partial to the beds designed by Australian manufacturer Birdies. These sturdy galvanized loft beds are very effective. They are galvanized with aluzinc, a material composed of 55% aluminum and 43.4% zinc with a small amount of silicon. Each container is designed with practicality in mind. Some even come in multiple configurations, allowing you to choose the exact size and shape you need!
Those of us with limited planting space might be interested in their range of galvanized planters and pots. The patio-balcony-deck line (CBD for short) is a great product line. Instead of corrugated metal, these opt for a sleek, sleek and streamlined design that can be seamlessly installed on porches and patios.
But if you have a lot of space in your garden, fear not! Their original collection is perfect for you. Both 15" and 30" depths are available. These beds offer a lot of square footage and can be configured to fit your space. I prefer their long and narrow configuration (about 5.25'x2'). But there are also options for squares or rectangles of other widths. These are great for growing vegetables and you'll be using them for decades.
Do you have a place that only has a round bed? Tall, round beds provide the perfect habitat for your potato plants, and the depth allows you to continuously add soil and expand your potato harvest. You can fill it with concentric rings of lettuce to make an eye-catching salad garden, or make an herb display. The options are endless!
DIY Build: Elevated Galvanized Steel Garden Bed
If you have galvanized sheet available, you may want to consider building your own DIY bed. Make sure you have good quality galvanized steel for roofing or other exposure to the elements. You'll also need wood corner posts to hold the steel, and some corner flash to protect the edges from scuffing.
There are many designs on the web for this type of bed, and a quick search will find a list of patterns and materials available to you. We also have over 50 raised bed types on our list! One thing I recommend, however, is to reinforce the sides of deeper beds with galvanized pipe. A short length of pipe knocked into the soil against the outside of the bed prevents the steel from bending outwards as it fills with soil.
One consideration for these DIY beds is that they do require wood and metal. Wood has a shorter lifespan than galvanized steel, so you may eventually need to replace corner posts and any other wood used in their construction. You may be able to extend the life of the post if you paint it with exterior paint first, but be careful to choose a product that won't seep chemicals into the soil.
Also, steel plates can have sharp edges, so you need to prevent potential injuries. It is necessary to make a top cover to cover the exposed edges of the steel. You can create a bench-like surface by attaching a 6- or 8-inch wide board to the top of the bed, screwing into corner posts to secure it. This will also hide the open end of the reinforcement tube.
Keep your metal loft bed safe
Galvanized steel is a sturdy material that can withstand most garden uses. But there are ways to make sure your containers are safe for decades to come!
Avoid using fresh chicken manure in the garden. As amazing as it is, its acidity will break down the zinc surface faster, putting the steel at risk of rusting. Instead, use composted chicken manure or other organic options.
Choose plants that will grow in neutral soil and keep the soil pH on the neutral side. At neutral levels, zinc is less likely to break down into the soil.
If you are growing acid-loving plants, consider using a liner. Heavy plastic prevents acid soils from coming into direct contact with metals. Just make sure the plastic only covers the sides for good drainage.
Modify heavy clay to loosen it up. Raised beds need well-drained soil to ensure they don't turn into muddy ponds. Additionally, clay is a very fine particle that can adhere to the sides of the bed, and a clumped layer of clay can damage zinc finishes more than sandy soils.
So what have we learned? Zinc coatings are safe enough for livestock feeding and watering. It is unlikely to seep into your food. Steel garden containers are less likely to get too hot for your plants. Most importantly, you will be able to grow healthy food in it. Commercial containers are available and are easy to assemble for quick installation. If you're comfortable with tools, you can also do it yourself. There are also ways to extend the life of your bed, which have been around for decades.
Not only is it safe to grow plants on galvanized steel beds, but you'll grow better food than you can get on the market.
