How to Build Raised Garden Beds

Benefits of a Raised Garden Bed

Gardens are often challenging for many reasons. However, you can overcome some challenges by building a raised garden bed. They are beneficial for:

  • Weed control—starting with fresh, loose soil precludes and makes controlling weeds easier
  • Health accessibility—planning for a wheelchair, bad back, or frail footing means gardening is feasible
  • Soil makeup—choosing the right mix or whether or not you grow organic or not is flexible
  • Animal resistance—using netting over your bed protects from rabbits, deer, squirrels, and birds better
  • Season length—planting seeds earlier right into the soil means growing seasons are longer
  • Building help—building a raised garden bed yourself is achievable

It just takes some planning, materials, and building according to your needs.

Mapping Out Plans

There are a few things to consider before you decide to create your masterpiece garden. Your garden space, unless you are specifically growing shade plants, requires six or more hours of sun a day. It needs to be within reach of a hose, soaker hose, or sprinkler system. Decide if you need a kit or you can DIY. You have options for how you want your raised garden bed to appear, such as corrugated metal, wood, cinder block. Measuring includes the yard but also what is accessible, how many raised beds you want or need, and how much space you have. It is dependent on the types of plants for how much space they need. Most importantly, you get to map out what you grow inside your raised garden bed!

Planning Guide for Raised Garden Beds

Let’s break it down to make it easier to plan toward your goal. 

Map Out Space

Map out the space you have available for your raised garden bed. Take measurements of the space that gets six hours or more of sun during the spring, summer, and, possibly, fall. (Remember if you are planning this during the winter that the sun moves according to the season, so what is sunny in the winter may not be sunny in the summer. Look to the south!) Add trees and whether the space is on the east, west, south, or north of your house or any other building, such as a neighbor’s house or tree that might cause shade. 

Determine the Size and Shape

Now that you know the available space, determine the size and shape of the bed. To be wheelchair accessible you need a smooth space to roll and u-shaped beds on stilts. The goal is to fit the wheelchair so the person can reach around three sides of them. Keep in mind that between beds the handicapped person needs to be able to turn around. The ADA recommends, “An accessible table has a surface height of no more than 34 inches and no less than 28 inches above the floor. At least 27 inches of knee clearance must be provided between the floor and the underside of the table.” This means the bottom of the stilted bed is no lower than 27 inches and the total height is 34 inches.

The more elevated the bed the easier it is on your back. Stilts are also an option. Stilts, however, may require a master craftsman with wood cutting and designing tools to help build it. If you don’t use stilts, the height of the bed could mean the difference between how much space there is for the roots of your plants and how much soil you have to purchase to fill the bed. It is best to give your roots at least ten inches of height and if you can afford the soil and need the ease build it as high as your construction is durable. 

However high it is, you need to be able to reach into all parts of the bed from one side or another. An average arm’s length is 25 inches. Shaving off a couple of inches gives you a four-foot-wide bed. The length is optional, according to your space and planting.

Plan Water Source

Unless you enjoy hauling bucket after bucket of water to your plants, particularly for those thirsty tomatoes, you need a faucet that feeds water through a soaker hose, sprinkler system, or the DIY-watering-hose nozzle. If you are soaking or sprinkling several beds, purchase a y-splitter to give yourself at least two water hoses per spigot. If you do not use a hose reel, watch out for the daydreaming mower!

It is particularly important that wherever you have your bed is not marshy or stays damp or cold. Your raised garden bed drains better than a typical garden bed. However, without good drainage the ground and garden bed walls become a water barrel of containment, rotting your plants from the roots up.

Choose Material

There are a lot of options for building the raised garden bed. Cinder blocks are easy and inexpensive. If you don’t like the grey institutional look, consider painting the outside. Another easy way to build a raised garden bed is by buying wood kits through your local hardware store or garden center. 

If you want to go the extra step and build a wooden or corrugated metal one yourself, make sure the wood is either pressure-treated or plain cedar and the metal is sealed. Untreated cedar is the way to go if you want to be purely organic, and it is the best wood for resisting insects and rot. Treated wood has a chemical footprint, but you can grow healthy, edible plants with a little space for roots not to suck on that chemical. Corrugated metal should be sealed to prevent rust. The rust is more metal than you want in your soil and in your body. 

Choose Soil Options

Before you start building, you want to make two important decisions. One is where the heck am I going to get all that soil, and what is the makeup of my soil? You have several options for where to buy soil or soil elements, such as garden supply stores, landscape companies, or through local advertisements.  As far as what you need to buy to create the best planting mix:

20-30% Compost

Do not add fresh compost or manure to your bed. It will burn the plants. You can create this from your vegetable waste or buy aged manure or compost from a landscape or garden supply store. However, it is easiest if you go ahead and purchase prepared compost.

40-60% Topsoil

Potting soil is too loose for the security of your plant roots and the stability of your plants. Garden or landscape supply stores are your best bet, but you can often purchase topsoil from individuals or companies in which the work involves digging. If you choose the latter, be careful the soil hasn’t come from a new development where the nutrients may have leached from the soil or from a place that may have used chemicals on or nearby the soil.

10-20% Aeration

For this percentage garden soil contains many elements good for drainage or you can use lava rock, also found at garden and landscape suppliers.  

Soil calculators such as the one found at Gardener’s Supply Co. website help you determine how much total soil you need for your raised garden bed size. You may also multiply the width, times the length, times the height to get the total cubic feet of soil you need.

Decide What to Grow

The final fun decision is what you want to grow. Do you want vegetables and herbs, flowers, flowers and herbs, a mix? If you mix your plants, particularly with herbs, you are less likely to have a pest problem, which means fewer chemicals or even an organic garden. Buy the seeds well in advance of the last frost because you get an early planting season with this garden.

Once you have some of the decisions mapped or listed out you are ready to build your raised garden bed.

Building

First, decide if you want a kit with which all the supplies and the instructions come prepared to easily piece together. These kits are found at hardware or garden supply stores.

Otherwise, you can build a basic four feet by eight feet by ten-inch high cedar, raised garden bed without a kit. You may vary it by adding to or subtracting from the size, shape, or accessibility of the bed. 

Supplies:

  • Shovel
  • Measuring tape
  • 4 ½’ x 8 ½’ wide mesh hardware cloth
  • Staplegun is helpful but optional
  • (If you don’t use rot-resistant materials other than cedar, plastic sheeting to line the sides of the box)
  • 2 8’ x 2” x 10” cut pieces of cedar (if you can’t cut yourself, ask the hardware store to do it)
  • 2 4’ x 2” x 10” cut pieces of cedar
  • 6 10” x 2” x 4” cut pieces for posts
  • Deck exterior or stainless steel screws
  • Compost, topsoil, garden soil 
  • Wood clamps
  • Drill

Construction:

  1. Measure out the place for the 8’ x 4’ garden bed according to the yard map you drew up earlier. 
  2. Use the shovel to cut down to the soil, removing the grass within your garden space.
  3. Clamp the wood together in preparation for screwing together the posts and sides.
  4. Drill holes where the screws go so the wood doesn’t split when you screw your walls together.
  5. Screw each of the 6 10” high posts within the garden bed walls—one at each corner and one in the middle of each of the longest sides. (If you didn’t use rot resistant material, staple in plastic lining inside all the walls)
  6. Set the garden bed walls within your cut space. 
  7. Either staple to the bottom insides or lay the hardware cloth on your garden floor. It prevents weeds but allows worms in your garden bed for a healthy home for worms and plants alike.
  8. Add your soil mix to the bed to 1” from the top (you don’t want the soil running over and out in rains or watering) Using the shovel tamp down the soil as you go. Don’t mash or step in the soil. You want a firm bed for the plants to stand in, yet you want the water and nutrients and roots to have room to breathe. If the soil is dry, add some water as you go to prevent the top of the whole bed from collapsing down when it rains or you water the seeds or plants.
  9. Finally, level off your bed in preparation for the exciting part!

Planting

Follow the instructions on the seed packets for how deep, when and whether to soak seeds to plant them. You want to avoid frost, but your raised garden bed will already be warmer than if you planted directly into the ground. Keep the soil lightly but consistently moist as the seeds prepare to grow. However, when the weather is warm you can buy young plants ready to grow. 

The instructions on the seed packets or young plants will tell you how far apart to thin or plant them. You want to plant them far enough that air can circulate, but close enough they cover the ground, preventing weeds. Also, plant them so taller plants don’t block the sun for shorter plants. You can set garden stakes for the climbers or less sturdy plants directly into your raised garden bed. Mix up the types of plants you grow in your raised bed for pest control. 

Speaking of pest control, if animals, such as squirrels with their nutty hole digging or rabbits and deer with the munchies are a problem, it is easy to construct or buy an easy netting over your garden bed to protect it.

After each growing season mix more compost into the top of your garden bed. 

Finally, and most importantly, enjoy the fruit of your labor for years to come both in your garden and the ease of a long-lasting, raised garden bed.

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