What You Need to Build a Basic Raised Bed

A raised garden bed is a wooden or composite box you fill with soil and plant into. You can build one in a weekend with basic tools and materials you can find at any hardware store. The most common design is a straightforward rectangular frame made from untreated wood boards, held together at the corners with screws or nails, then set on level ground.

The standard size is 4 feet long by 2 feet wide by 12 inches deep, though you can adjust these dimensions to fit your space and what you want to grow. Deeper beds (18 inches) work better for root vegetables like carrots and potatoes. Shallower beds (8 inches) are fine for lettuce and herbs. The length and width matter less—pick what fits your yard and what you can reach comfortably from both sides without stepping into the bed.

You will need untreated wood boards (cedar, composite, or untreated pine), exterior-grade screws, a drill with a screwdriver bit, a level, and a tape measure. Do not use pressure-treated wood, which contains chemicals that can leach into soil over time. Avoid railroad ties for the same reason. Cedar naturally resists rot and lasts 10 to 15 years. Composite boards cost more but last 20+ years and never rot.

Key Takeaways

  • A basic raised bed is a wooden frame filled with soil, built from untreated boards held together with exterior screws at the four corners.
  • Standard dimensions are 4 feet by 2 feet by 12 inches deep, but you can adjust depth based on what you grow—root vegetables need 18 inches, leafy greens need 8 inches.
  • Use untreated cedar or composite boards; pressure-treated wood and railroad ties contain chemicals that can contaminate soil.
  • The entire build takes 30 to 60 minutes with basic tools: a drill, screwdriver bit, level, and tape measure.
  • Set the bed on level ground, fill it with garden soil (not topsoil alone), and water it thoroughly before planting.

Choosing Your Wood and Sizing the Frame

Cedar is the most popular choice because it resists rot naturally and looks finished without stain or paint. A 4-by-2-foot bed typically uses four boards: two that are 4 feet long and two that are 2 feet long. For a 12-inch-deep bed, buy boards that are 12 inches tall (often labeled as 1-by-12 lumber, though the actual dimension is closer to 11.25 inches). If you want a deeper bed, buy 2-by-12 boards instead, which are roughly 11.5 inches tall, and stack two of them on top of each other.

Composite boards (made from wood fiber and plastic) cost 50 to 100 percent more than cedar but do not rot, splinter, or need sealing. They are heavier to work with and can warp slightly in extreme heat, but they last decades. If budget is tight, cedar is fine—you will replace it in 10 to 15 years, which is reasonable for a garden structure.

Before you buy, measure your space and decide whether you want one bed or multiple beds in a row. Multiple smaller beds are easier to reach into and manage than one very long bed. Two 4-by-2 beds side by side take up the same footprint as one 4-by-4 bed but give you more flexibility.

Building the Frame Step by Step

Lay the four boards on a flat surface in the shape of a rectangle. Position them so the ends overlap at the corners—the 4-foot boards will sit on top of the 2-foot boards, or vice versa. This overlap is where you will drill your screws.

At each corner, drill two holes through the overlapping boards using a drill bit slightly smaller than your screw diameter. Use 3-inch exterior-grade screws (stainless steel or coated steel). Drill the first screw about 2 inches from the top of the board and the second about 2 inches from the bottom. This prevents the wood from splitting and holds the corner rigid. Repeat at all four corners.

Once the frame is assembled, flip it over and set it in its final location. Use a level to check that the frame sits flat on the ground. If one corner is higher than the others, dig out soil under the high corner or add soil under the low corners until the frame is level. A bed that is not level will have water pooling in one corner and drying out in another.

Preparing the Ground and Filling the Bed

Before you fill the bed with soil, remove any grass or weeds from the ground inside the frame. You can pull them by hand, scrape them away with a shovel, or lay cardboard over the area and let it kill the grass underneath over a few weeks. If you skip this step, grass will grow up through your bed and compete with your plants.

Fill the bed with garden soil, not topsoil alone. Garden soil is a blend of topsoil, compost, and other organic matter that holds moisture and nutrients. Topsoil by itself is too dense and drains poorly. A 4-by-2-by-12-inch bed holds about 8 cubic feet of soil, which is roughly one cubic yard. Buy bagged soil from a garden center or order bulk soil delivered if you are building multiple beds.

Water the soil thoroughly after filling. It will settle over the first week or two, and you may need to add more soil to bring it back to the top of the frame. This settling is normal and does not mean you did anything wrong.

Anchoring the Bed So It Does Not Shift

A raised bed filled with soil weighs 500 to 800 pounds depending on size and soil type. Over time, especially if you live in a freeze-thaw climate, the frame can shift or bow outward. You can prevent this by anchoring the bed to the ground.

The simplest method is to drive 12-inch metal landscape stakes through the outside of the frame into the ground. Use two stakes per long side and one stake per short side, positioned roughly in the middle of each board. Drill a hole through the board first so the stake does not split the wood, then hammer the stake through the hole and into the ground. The stake should be flush with or slightly below the top of the board so it does not interfere with planting.

If you are building on very soft or sandy soil, you may need longer stakes or more of them. If you are building on hard clay or rocky ground, anchoring may not be necessary—the bed will sit firmly on its own.

Finishing Touches and Maintenance

You do not need to seal or stain untreated cedar. It will weather to a gray color over time, but the wood underneath remains sound. If you prefer the look of stained wood, use an exterior wood stain that is safe for vegetable gardens—avoid paint, which can peel and flake into soil.

In the first year, the soil will settle and compact. Top it off with 2 to 3 inches of compost each spring to replace what has broken down and to keep the bed at full depth. After 10 to 15 years, cedar boards will start to rot at the base where they touch soil. When that happens, you can replace individual boards or rebuild the entire frame.

Composite beds need almost no maintenance beyond occasional cleaning. If they warp slightly, they usually straighten out again when the temperature changes. They do not need staining or sealing.

Frequently Asked Questions

Can I build a raised bed directly on top of grass without removing it first?

You can, but grass will grow up through the soil and compete with your plants. Removing it first takes an extra hour but saves you months of weeding. Lay cardboard over the grass before filling the bed if you want to avoid digging—the cardboard will decompose and the grass underneath will die.

How deep does a raised bed need to be?

It depends on what you grow. Leafy greens like lettuce and spinach need 6 to 8 inches. Tomatoes, peppers, and herbs need 12 inches. Root vegetables like carrots, beets, and potatoes need 12 to 18 inches. If you are growing a mix, 12 inches is a safe middle ground.

What is the difference between garden soil and topsoil?

Topsoil is the top layer of natural soil, usually dug from construction sites. It is dense and does not hold moisture well on its own. Garden soil is topsoil mixed with compost and other organic matter, so it drains better and holds nutrients. Always use garden soil for raised beds.

Do I need to line the bottom of the bed with landscape fabric?

No. Landscape fabric can trap water and prevent drainage. If you are concerned about burrowing pests like moles or gophers, you can lay hardware cloth (a metal mesh) on the ground before filling, but most gardeners skip this step. Removing grass beforehand is usually enough.

Can I use treated wood for a raised bed?

Pressure-treated wood contains chemicals that can leach into soil over decades. Untreated cedar or composite boards are safer for vegetables and herbs. If you already have treated wood, you can use it for ornamental beds or cover the interior with landscape fabric as a barrier.