Let’s get you started on building your first raised bed. First we’ll look at what its walls need to do. Then we’ll consider the best materials.

Requirements for Your Raised Garden Bed Walls

The bed walls contain fertile soil over infertile ground. Any material that can hold in the soil while standing up to watering and the weather would probably work.

Bed walls help protect your veggies from pests. Bed walls keep my veggies safe from gophers. They’re too high for gophers to scale and too tough for them to gnaw through. I can also attach a gopher wire floor to the walls to keep gophers from tunneling up into the bed.

Bed walls can double as a foundation or scaffold for garden covers on hoops. Hoops can support mesh or clear plastic covers. With a clear plastic cover, your raised bed doubles as a hot box. With a mesh cover, your veggies are protected from flying pests.

Raised bed walls double as a container for composting. Make sure your bed walls are sturdy enough to withstand tilling and shoveling.

Overall, raised beds are meant to boost productivity at minimal expense. They’re meant to help you focus both your work and budget on growing and harvesting. So choose materials that are cheap, readily available and easy to work with, yet meet all of your garden requirements.

The challenge is to find the materials that meet all your requirements. Let’s look at four options to see how they stack up: masonry, metal, lumber, and wooden sheets.

Concrete and Masonry

Given their low cost, ease of use, sturdiness, durability, and damp resistance, concrete and masonry are probably the best choice for raised bed walls. Their drawbacks include the sheer permanence of the finished bed and the time it takes to set up the forms and cure the wet cement.

Mortarless (Dry Stacked) Cinder Blocks for Raised Garden Bed Walls

Forget the cure time by stacking two tiers of cinder blocks for your bed wall. You may need a total of 30 or 40 blocks for a four foot by eight foot bed. If you stagger the tiers, a dry fit wall (no mortar – simply stacked) ought to contain soil on account of the width and the weight of the blocks. Much depends on leveling the ground beforehand. The ground needs to be smooth, flat and level so the blocks lay straight. It helps to brace the blocks in place with spikes. For example, you could pound  in rebar spikes through the hollow centers. You could do this to keep the corner blocks from wandering out of place, and to brace the midpoints of walls longer than four feet.

The downside of cinder blocks is their price. You pay a premium for a finished concrete product. You can expect to pay $150 for the cinder blocks alone, for three raised beds.

Poured Concrete for Raised Garden Bed Walls

To benefit from the economy of scale, consider pouring or molding the walls from wet concrete. 

If you’re planning on building a lot more than three beds, then the savings from mixing your own concrete start to accrue. 

Here’s my cost breakdown: you can pay for ready mix concrete to be delivered and poured into forms, but you’ll have to build all the forms in advance, which might become a bigger chore than building raised beds from another material. Instead, you can mix your own concrete in small batches, using a rental cement mixer or a good wheelbarrow. You’ll also save a lot by starting with a large pile of delivered aggregate sand and gravel and a few 100 pound bags of cement powder. Then you can pour wet concrete into forms, which you can reuse for an unlimited number of additional beds. However, you’ll need to let each poured wall cure for a few days. The four walls for a single bed will take more than a week to pour and cure in quick succession. You’ll also pay for steel rebar and/or heavy gauge wire mesh to reinforce the poured wall sections. Ultimately, you’ll produce a number of raised beds that will last a very long time, well beyond the gardening days of your great grandchildren.

Ferrocement for Raised Garden Bed Walls

If you fancy concrete but want to keep things small, consider ferrocement. Ferrocement is proven material for water tanks, boat hulls, garden planters and more. It’s based on portland cement, but made with finer aggregate than poured concrete. You trowel a fairly thick mix of this into several layers of wire mesh.

For a raised bed, wire together multiple layers of wire mesh into walls that surround any shape of bed you wish. You can even include recurved edges on top to keep out slugs. The wire mesh will support the wet mix and then reinforce the cured cement. You start with a stout wire grid, such as those used for poured concrete, then fill in the spaces with finer wire mesh, such as hardware cloth or chicken wire, in a few layers. Then you’ll mix small batches of concrete using fine aggregate and sand rather than coarse gravel. The mix needs to be wet but not too sloppy so you can trowel it into the spaces and voids of the metal mesh and have it stay put. The idea is to completely fill all the voids while completely covering all of the wire. You’ll end up with a thin wall of wet concrete supported by the wire mesh that’s only one or two inches thick, overall. When it ultimately cures, the ferrocement structure will be sturdy enough to withstand all kinds of gardening and composting punishment. The shape and profile of ferrocement walls are limited only by your imagination. Again, they may even include slug proof recurves. 

Ferrocement was my first choice for wall materials, but I was too short on time. The planting season was already upon me.

Metal Sheet and Metal Mesh

Corrugated, Galvanized Steel Sheet for Raised Garden Bed Walls

One of the most popular materials I’ve seen for raised beds is galvanized and corrugated steel sheet. This material ranges from flimsy, ultra light sheets (that you can assemble from a kit shipped to you by Amazon) to super heavy duty material used for culverts and granaries.  All grades of corrugated steel are galvanized. That means they’re coated with a layer of zinc, to protect the steel from corroding. The idea is that the zinc corrodes preferentially owing to its electrochemical properties, leaving the coated steel intact. That way, a much lighter gauge of steel can be used. Corrugation stiffens the sheet quite a bit. Again, this lets you get away with a much thinner gauge than otherwise.

I’ve got two raised bed planters made from the lightest gauge, shipped unassembled in a box with a hundred nuts and bolts. They’re four feet long by two feet wide and just over a foot tall. The empty bed walls are quite light and flimsy, but have stood up to a year of weather and gardening, with only a couple of dents from rakes falling on them.

Sometimes you’ll see planters made from heavy gauge sheets meant for granaries, culverts, or livestock watering troughs. This material seems to work perfectly for large beds that are used for intensive veggie production.

Otherwise, a surprisingly light gauge of corrugated sheet will hold in the soil and stand up to a  fair amount of wear and tear in your garden. You can expect to see some dents.

Galvanized Chicken Wire or Hardware Cloth for Raised Garden Bed Walls

I’m only speculating about this material for bed walls. I envision walls built from a choice of two types of galvanized steel wire mesh. The first is a square or rectangular mesh known as hardware cloth, while the second is made from wire twisted into a hexagonal, honeycomb mesh, known as chicken wire or gopher wire. Both are galvanized steel wire. For both, you’ll need to build a frame to support the mesh. The mesh should have no problem holding soil if the soil contains enough composted organic fiber.

My confidence in this wall material is based on my experience with a composter that I built as described. The hardware cloth walls of the composter held in the compost quite effectively, for several years. The whole structure was light, durable and easy to swing open or move, to turn the compost.

Solid Wooden Lumber

Treated lumber is worth your consideration. The restrictions and outright bans on the nastiest wood preservatives will keep arsenic and chromium out of your garden. I believe the currently applied preservatives are based on copper. Do your due diligence to make sure that wood preservatives don’t contaminate your garden. In any case, line the inside of your bed walls with a plastic sheet moisture barrier.

As an alternative, consider untreated, rot resistant wood, such as cedar or pine. Again, isolate the wood from the ground and the moist soil within the raised bed, by lining the inside and lower edges of the bed wall with a durable plastic sheet. Rolls of black plastic sheet (sold as mulching cover or architectural moisture barrier) are ideal. The clear stuff is far more prone to sun damage, leaving it in tatters after a single season. Leave plenty of excess sheet to overlap the top of the wall, then staple it into place. As the soil in the bed compacts and subsides over time, it will pull the sheet down with it, so leave plenty of excess sheet to overlap the top of the wall.

Plywood and other Wooden Sheet Products

Exterior grade plywood and oriented strand sheet provide good alternatives to solid wood or lumber.

I couldn’t find anyone using plywood for raised garden beds, so I tested it myself.

Construction Details: I used a single sheet of three eighths inch thick exterior grade douglas fir plywood for each four foot by eight foot by sixteen inch deep bed. I glued and screwed 2×2  stringers along all the outside edges of the wall panels (both four and eight feet long), with treated wood stringers in contact with the ground. Then I fastened the four foot end walls to the eight foot side walls by driving deck screws through the stringers at the corners. I finished the beds by attaching a gopher wire floor with fence staples driven into the bottom stringers, and by stapling black plastic mulching sheet in place to line the inside of the plywood walls.

After one year of service, the five plywood raised beds I built are all still in excellent shape. Gophers have yet to penetrate the walls or the gopher wire floors. The plywood is showing some signs of weathering but this is pretty much limited to discoloration, with no visible delamination or splintering. So I am quite pleased with my work. 

Done.