Galvanized Raised Garden Beds

Galvanizing is a way of protecting steel with a layer of zinc. There are two common methods:

• Hot-dip galvanizing. Finished steel is dipped in molten zinc at around 840°F. The zinc bonds with the steel surface and forms a thick, tough coat. Stock tanks are made this way.
• Pre-galvanized sheet. Steel coil is zinc-coated at the mill, then cut and rolled into panels. The coat is thinner, and cut edges are not coated, which is why bed edges are often rolled or capped.

Zinc protects steel in two ways. It's a barrier that keeps water and air off the steel. And because zinc corrodes before iron does, it "sacrifices" itself at small scratches, so a nick in the coating doesn't rust right away. That self-healing effect is what sets galvanized steel apart from painted steel.

Plain galvanized beds have the classic silver look that fades to matte gray. Many newer beds use a different base coat or add a finish on top:

• Aluzinc (Galvalume): an aluminum-zinc coating that usually resists corrosion longer than zinc alone, especially in wet or salty air.
• Powder coat: a baked-on paint layer over a galvanized or aluzinc base. It adds color and another barrier, but chips need touch-up paint.
• Plain painted steel: cheaper and short-lived once the paint cracks. Not a good choice for a long-term bed.

On safety, the three are similar. On looks and lifespan, coated beds tend to win, at a slightly higher price. Our metal vs wood vs fabric comparison puts all of these against cedar and fabric.

1. Pick the spot. Most vegetables need 6 to 8 hours of direct sun. Leave paths of at least 18 to 24 in around the bed.
2. Prep the ground. Remove sod or cover it with plain cardboard. Lay ½-in hardware cloth under the bed if gophers or voles are a problem.
3. Assemble loosely, then square it. Measure both diagonals and adjust until they match, then tighten every bolt.
4. Install the braces. Use the cross ties or center supports that come with longer and taller beds.
5. Fill with a good mix. Blend roughly six parts screened topsoil to three parts compost and one part perlite or bark fines. For a 4x8 bed filled 12 in deep, plan on 32 cubic feet, or a little over one cubic yard.
6. Mulch and water. Add 2 to 3 in of mulch to keep the soil cool and moist next to the metal.

If you'd rather buy than source parts, one option is a galvanized bed from Thrive Garden. Our guide to raised garden bed kits explains what any good kit should include.