How to Build a 4 by 8 Raised Garden Bed

It’s not hard build a 4 x 8 raised garden bed out of wood with just a few tools and a minimal amount of material. You can actually build raised beds out of pretty much anything you want…wood, stone, blocks or just pile up soil in a mound.

However, the most efficient method is to build your raised beds out of wood while using a simple design. You can place as many boxes around your backyard as you want and make a great looking garden space.

Types of Wood for Building Raised Beds

You need to decide what type of wood to use and how tall you want the bed. There are several types of wood that are acceptable to use, but cedar is usually the wood of choice for many gardeners. It is naturally rot resistant and lasts longer than most other woods. You can expect a red cedar bed to last from 10-20 years.

IMPORTANT NOTE: Don’t used treated wood. A lot of people do, but if you’re serious about organic gardening, stick with natural, rot resistant options. Referenced in the Organic Gardening Certification Guide and as widely reported, “…no pressure-treated wood is allowed in soils used to grow organic food. If you want to meet this high standard, choose a different material.”

Height of bed

You can build your bed as high as you want, but typically beds are more commonly built to be 11 inches high. That’s the exact height of two boards that are 2” x 6” stacked. This type of bed will leave the bottom open without underlayment so that roots can access deeper in the ground. If you decide on higher walls, you’ll need to add cross-supports to keep sides from bending outward from the weight of the soil. It’s recommended to use cross-supports on walls that are higher than 18” and longer than 6′.

Width and length

The best width for raised beds are 4′ wide. This makes it easy for a gardener to reach all areas of the planting space. You can also more easily position the beds in any configuration you choose. The bed can be any length you want, but remember to install cross-supports every 4”-6” along the length of the bed.

Tools

Screwdriver, hacksaw, drill, mallet, square, handsaw, level, clamps, post hole digger

Materials for one 4′ x 8′ bed

  • 8 – 2” x 6” cedar boards
  • 4 – 4” x 4” corner posts cut to 12” longer that you bed height (if bed is longer than 8′, add extra posts to use for mid-span every 4′-6”)
  • 3.5″ #10 coated deck screws (6 screws for each corner and each extra mid-span post)
  • 1” stainless screws for cross-supports if needed
  • 1/2″ aluminum flat stock (usually in 8′ lengths at hardware stores)

Putting it all together

This type of raised bed is best assembled on site, since the end posts will be staked in the ground and the box leveled to suit the terrain.

Step 1:

Cut your lumber to specs and layout your pieces for easy assembly.

build a raised bedImage Credit: Screenshot/Youtube

Step 2:

Attach the end posts to planks to form bed box. If you’re doing this by yourself, you may want to use clamps to hold them in place while you screw them together. (If you’re bed is longer than 8 feet, remember to add extra posts mid-span for additional support. This where you will also add your aluminum cross-braces end to end for extra support, if needed.)

how to build a raised bedImage Credit: Screenshot/Youtube

Step 3:

After attaching the end posts, your new 4′ x 8′ bed frame should look like this.

build a 4 x 8 raised bedImage Credit: Screenshot/Youtube

Step 4:

Next, measure and mark where you will need to dig your post holes. Digg 4 holes 12” deep to place your corner posts. A post hole digger will do the job easily.

how to build a raised garden bedImage Credit: Screenshot/Youtube

Step 5:

Turn over the soil where you will be placing your new bed. You will have already measured the rectangle sized bed for your post holes, so just dig up the new soil between the post holes before you place the bed. You will compete the building of your garden soil by filling in with more top soil (if needed), nutrients and compost after you have permanently placed your bed.

Step 6:

After you have tilled or dug up your top soil for your bed, place your new bed box into the post holes. Be sure to level your bed in order to have good drainage. This may require adjusting the post holes to raise one side or the other to achieve proper leveling.

raised garden bedImage Credit: Screenshot/Youtube

raised wooden garden bedsImage Credit: Screenshot/Youtube

Step 7:

After you’ve leveled all sides and are satisfied with how your bed box sides, fill in the holes and scoop up dirt around all sides to close up the bed. You’re ready to fill your bed (up to about 3” at the top) with nutrient rich soil and plant.

Here’s a completed 4′ x’ 8′ raised bed, ready to be planted.

raised bedsImage Credit: Screenshot/Youtube

You can build one or more of these really simple, functional 4 x 8 raised garden beds and lay out a great garden design anywhere you want. You’ll be surprised at how much easier gardening in raised beds is and how much harvest small space gardening can yield.

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