Building a Raised Bed

Updated November 2021

Raised garden beds are recognized to be the best growing conditions for growing veggies. The soil warms faster, as it is above ground, and stays looser longer without compacting. Tomatoes, peppers, lettuces and other vegetables grow quickly, and their roots can more easily spread out within a given season. Here are some ideas for building a raised bed.

Planting in a raised bed keeps the soil loose and oxygenated, because it doesn’t get walked on. This means young roots can spread out more easily and become established right away, giving the plant a solid foundation so that it can focus its energy later in the season completely on fruiting.

Also, you can plant earlier in the season because the soil is warmer when it is above ground. In some cases I’ve gotten tomatoes into the raised beds a full month prior to in-ground plants. Additionally, you are providing better drainage, and you can amend and/or replace the soil more easily between growing seasons.

Perhaps most importantly, raised beds are graceful and add an elegant hardscaping element to any backyard, whether urban or country.

Building a Raised bed - gardening — Raised beds can be used as an architectural element to increase a property’s interest or provide a focal point

So many of us turned to building raised beds for new or expanded garden space at the beginning of 2020, finding ourselves at home for longer periods with time on our hands. One of the benefits of making your own bed is that you can size the bed accordingly to your space. You can also convert patio areas, or other small spots near the back door where digging is not viable.

A traditional raised bed size is 4×8 (this is easy to make because standard lumber comes in 8’ lengths). However I’d encourage anyone to think outside the box when it comes to raised bed shapes. If you have a small or a narrow but long space, such as along the side of the house, it’s easy to make raised beds to whatever size you need. In fact, I’ve found long and skinny beds to be really easy to plant and manage. With only one or two rows of plantings, it is easy to reach all the way around all of the plants and soil for maintenance and harvesting.

While you can design a bed to whatever size or shape works for you and your space, I would not recommend making your raised bed much wider than about 4 feet, unless you have super long arms. I really wide bed makes it difficult to reach across to the middle of the bed. And you want to avoid walking on the soil as much as possible.

Here are the basic steps to get started building your beds:

Step 1 – Calculate your lumber

When building a raised bed you should get lumber that is either 8 or 12 inches wide. If you have the space, making a 4 x 8 box is easiest, as per above, and it reduces any lumber waste. Just purchase 3 @ 8 foot long boards and cut one in half. Repeat for multiple beds or for double height beds.

Taller beds are great as they reduce bending over and possible back strain. This option becomes more and more attractive as we become ‘veteran’ gardeners. While it can be harder to remove or maintain the soil at the bottom of the bed, or to replace your hardware cloth deterrent for burrowing animals., the benefit in having more warm soil space and plants up at eye level makes it worthwhile.

If you decide to go this route, use wider boards (2 x 12), and stack them three (or four) tall. This means that for a 4 x 8 bed, you’ll need 9 boards per bed for a 3 foot tall box, or 12 boards for a four foot tall box.

Another option is to elevate your bed off the ground or patio by adding legs. Just make sure to accommodate for all of the weight of the soil in your bed. Elevated beds usually can’t be as big as those on the ground due to the weight. Use 4 x 4 lumber as a minimum for the legs. You will need a lot of soil which will compact over the course of the first month.

Purchase redwood or cedar; these are the most rot resistant types of wood which are commonly available. Treated lumber is not currently allowed in soils used to grow organic food. While since 2003 they have removed the arsenic in treated lumber, they still use copper compounds and fungicide, so if you want to avoid these compounds potentially leaching into your soil, go with the untreated redwood.

Step 2 – Assemble the box.

Screws last much longer than nails when exposed to the elements. Use at least three screws per corner, with one going in the opposite direction as the other two. Utilizing a 4 x 4 in the inside corner will ensure a sturdy fit. (You can cut the 4 x 4 short so that it is hidden under the soil). Alternatively, Panacea makes some awesome raised garden bed corner brackets. These make building the bed super easy, because you just need to slip the lumber into the steel corners and screw in place using the template screw holes.

If you’re making the taller bed, you can use these Easy Raised Garden Corner Bracket connectors to secure the stacked boards together. This product doesn’t have the top edge so you can make the sides taller. Or, for a lovely dragonfly flair, try the Bloom Instabrace.

Building a Raised bed allows you to intersperse flowers with your vegetables — Here you can see the corner lumber holding the “layers” of wood together

Step 3 – Hardware cloth

If you have any burrowing critters like gophers or moles, you will want to staple hardware cloth to the bottom of the bed, assuming you are putting the bed on the ground. If you elevate your bed with legs you don’t need to worry about this!

Hardware cloth will last longer than poultry netting (chicken wire). It is more costly, but will outlast chicken wire by a good 4-5 years; in my experience. Chicken wire only lasts underground about 2 or 3 years, but hardware cloth will last 6 or more.

Make sure to secure the hardware cloth to the wood with closely placed staples or fence nails. Otherwise pocket gophers could still get in between the wire and the wood. Trim any wire hanging over the edge.

Step 4 – Water barrier

Staple water barrier paper around the inside of the wood. While this is not a critical step, it does protect the wood from rot and your frame will last considerably longer.

Step 5 – Trim or Edging

The last step when building a raised bed is to consider what type of edging you would like on your raised beds.

Many beautiful raised beds have a flat trim along the top edge for good looks. Depending upon the height of your bed, you can also use this trim as a seat. Other options are to trim the corners with lights or to add galvanized metal to the sides.

If your beds are a a single layer (8 – 12 inches tall), you may want to consider adding posts at each corner. Corner posts help when making taller beds, as they will serve to hold the layers together. But even if you are making the traditional low raised bed, the post is something to consider. They allow you to wrap plastic netting around your tender sprouts to protect them from nibbling rabbits, free-range chickens, groundhogs, raccoons, rats; anything that wants to eat your tender veggies as much as you do. They also allow you to secure your tomato cages or bean supports to something so that they won’t blow over in the wind. You can also use the posts to attach a sun shade to facilitate hardening off little seedlings you’ve grown inside.

Adding posts to the raised beds when building gives greater versatility for barriers and shade block

Location of your raised bed

Choose a sunny spot in your yard to locate the raised beds. If you can, the southern side is usually the best location, unless there are large trees or some other buildings there, casting shade. Before you lay down your bed, you should loosen the ground below where the raised bed is going to go. This gives the veggie roots more room to spread out!

If you choose to put your raised bed on top of a concrete patio, know that some concrete might leach lime. Generally vegetable roots need approximately 8 inches of space, however you might want to increase the height of your bed to give space away from the concrete. Or, just consider a water barrier on the bottom of the bed but above the patio.

Building a raised bed - Raised beds can be made of many materials — Here, pieces of broken concrete have been used to build a flower bed demarcating the boundary between the vegetables and the patio

The soil you put into the bed should be the very best soil you can get your hands on. Try to aim for 50% good garden soil (avoid fir bark type soil) and 50% compost. Each year you will want to add more compost to refresh the nutrients after every growing season.