How to Build a Raised Bed Garden

You can find a myriad of options and plans for building a raised bed, but I’ll share the most basic plan.

Preparing Your Site

The most important part of preparing your site is making sure it is level. Measure out the bed size and check its slope with a leveling tool. If there is any slope to the ground, you may need to scrape one side until the land is level on all sides.
If your ground contains pernicious weeds or grass, lay down an organic barrier, such as cardboard, to smother them. An alternative is to simply scrape the top layer of vegetation and turn it over; it will compost into the soil over time. If you think you may have rodents such as voles or moles, you will need a permanent barrier (hardware cloth, for example) because organic barriers will eventually break down into the soil.

Materials and Tools Needed

If you’re willing to pay for convenience, purchasing raised bed kits is an option. But to save money and go the DIY route, you’ll need these tools to construct a standard 4-by-8-foot, 10-inch-high raised bed:
•    3 (2-by-10-inch-by-8-foot) pieces of lumber (or 2 by 8 inches or 2 by 12 inches, depending on how tall you want your beds)

• Measuring tape
• Pencil
• Carpenter’s square
• Circular saw or handsaw
• Drill or impact driver
• 12 (2½-inch) deck screws
• Roll of ¼-inch hardware cloth (optional)
• Staple gun (optional)
• Level

The most durable and budget-friendly wood is pressure-treated pine, widely available at home supply stores. However, there is a lack of research showing whether chemicals used in the treatment process leach into the soil and at what levels (if any) those chemicals are taken up by plants. You can check with your local home center or lumberyard to find out what rot-resistant natural wood options are available.

Building Your Raised Bed

Once you gather the materials, set aside a few hours to build your raised bed. Though it can be built by one person, an extra set of hands is always useful.

1. Take one 8-foot board and mark it with the pencil 4 feet from the end. Use a carpenter’s square to draw a vertical line across the board.
2. Cut the board at the vertical line with a saw.
3. Lay out the four pieces of board in the shape of a rectangle: the two 8-foot sections parallel to each other and the two 4-foot sections parallel to each other.
4. Situate one 8-foot board perpendicular to one 4-foot board, where their ends meet flush.
5. Position the other corners of the raised bed the same way.
6. Using the drill, pre-drill the holes. Then, screw each of the four corners together where the boards meet, using three deck screws per corner.
7. If you’re using hardware cloth to cover the bottom of the bed (this prevents ground-dwelling rodents from getting to your plants from underneath), spread the cloth over the bed, stapling it in place. If it doesn’t cover the entire bed and you have to use two strips, make sure you have a 6-inch overlap between strips.
8. Carry the bed to its site and position it. Set the level on each of the four sides, ensuring the bed is level in all directions. If the bed isn’t level, use a shovel to scrape down higher areas of dirt until the bed is level.

These plans can be modified for differing dimensions, but you should never exceed 4 feet in width. You want to be able to reach into the middle of the bed. If your bed will be next to a fence or other area, make it no wider than 3 feet. The length of the bed is up to you.
Many people prefer taller raised beds. For a bed taller than 12 inches, you will need more than one board for each side. In this case, each corner will need to be anchored by a 4-by-4-inch post, with each side board screwed into the post instead of into the perpendicular side board.

Filling and Sectioning Your Raised Bed

For a raised bed, you want a slightly “heavier” medium (soil mixture) than for a container garden. A higher proportion of topsoil and compost adds moisture retention and nutrients. We will explore raised bed soil mixes later in this chapter.
As you begin planting your vegetables, think about the orientation of your raised bed, especially in regard to larger and taller plants.
Plants that grow vertically or taller than others should be planted on the north, east, or northeast part of your raised bed. Lower-growing plants should go on the south, west, or southwest side. This way, tall crops, such as tomatoes or pole beans, do not shade shorter crops, such as peppers or sweet potatoes, from the much-needed southwesterly sun exposure. The exception is if you plan to grow cool-weather crops, such as greens, further into the summer. These crops benefit from afternoon shade and may grow longer before bolting if provided with shade. (For gardeners in the southern hemisphere, these cardinal directions will be opposite.)

Can I use wood from an old fence or deck to build my raised bed? 

Pressure-treated wood manufactured prior to 2003 contains chromated copper arsenate (CCA), which isn’t considered safe for vegetable gardens. In 2003, the pressure-treating process changed to alkaline copper quaternary (ACQ), which the Environmental Protection Agency considers a safe alternative. It's a personal decision, whether to use pressure-treated wood, but if you do, I recommend staying away from any manufactured prior to 2003.