The simplest way to build a raised bed
A raised garden bed is a wooden or composite box you fill with soil and plant into. The fastest way to build one is to buy untreated cedar or composite boards, cut them to length if needed, and screw the corners together—no digging, no concrete, no special tools beyond a drill. Most people finish a 4-by-8-foot bed in under an hour.
The boards sit directly on the ground. You do not need a foundation, a frame underneath, or a bottom. Soil settles and compacts over time, so you will refill it each spring, but that is normal and expected.
If you want something faster still, you can buy a pre-assembled raised bed kit and bolt the sides together in your yard. If you want something cheaper, you can use untreated pine or reclaimed wood—it will rot in five to seven years instead of fifteen, but it costs less upfront.
Key Takeaways
- Untreated cedar boards last 10 to 15 years and cost $2 to $4 per linear foot; composite boards last 20+ years and cost $4 to $8 per linear foot.
- A 4-by-8-foot bed 12 inches deep requires eight 8-foot boards, four corner brackets or L-brackets, and 16 to 20 exterior-grade screws.
- Screw the corners together on flat ground, then slide the assembled box into place and fill it with soil—no digging required.
- Untreated wood is safe for vegetables; pressure-treated wood from before 2004 should not touch soil, and newer pressure-treated wood is safe but unnecessary.
Choosing your boards and materials
Untreated cedar is the standard choice. It resists rot naturally, does not leach chemicals, and lasts 10 to 15 years. A 2-by-10-inch cedar board costs $2 to $4 per linear foot at most lumber yards. For a 4-by-8-foot bed, you need eight 8-foot boards (four for the long sides, four for the short sides, stacked two high).
Composite boards are made from wood fiber and plastic. They do not rot, do not need staining, and last 20 years or longer. They cost $4 to $8 per linear foot and are heavier to move. If you plan to keep the bed for a decade or more, composite pays for itself.
Untreated pine is cheaper than cedar—about $1 to $2 per linear foot—but rots in five to seven years. It works if you are testing the concept or expect to rebuild in a few years.
Do not use pressure-treated wood from before 2004; it contains arsenic. Pressure-treated wood made after 2004 is safe for vegetables, but there is no reason to buy it when untreated cedar costs the same.
Fasteners and corner options
You need fasteners to hold the corners together. The two most common methods are exterior-grade wood screws and L-brackets.
Screws are the easiest for a first-time builder. Use 3-inch exterior-grade deck screws (galvanized or stainless steel so they do not rust). Drill a pilot hole first to prevent splitting, then drive two screws through the end of one board into the side of the adjacent board at each corner. You need 16 to 20 screws for a standard bed. A cordless drill makes this fast; a hand screwdriver works but takes longer.
L-brackets are metal brackets bolted to the inside corners. They are slower to install but create a very rigid joint. Use stainless steel or galvanized brackets rated for outdoor use. You need four brackets per bed, one at each corner.
Some people use both: screws to hold the boards in place while you work, then brackets bolted on the inside for strength. This is overkill for most home gardens, but it does create a bed that will last decades without wobbling.
Assembling the bed on level ground
Assemble the bed flat on the ground before moving it into place. Lay out two long boards parallel to each other, about 4 feet apart. Lay the short boards across the ends, forming a rectangle. Check that the corners are square by measuring diagonally from corner to corner—both measurements should be equal.
Drill pilot holes and drive screws through the end of each short board into the side of each long board. Two screws per corner is standard. If you are using L-brackets, bolt them to the inside corners after the screws are in.
Once the frame is assembled, slide it into its final location in your yard. It does not need to be perfectly level—a slight slope is fine and actually helps with drainage—but avoid placing it on a steep hill or in a low spot where water pools.
Preparing the ground and adding soil
You do not need to remove grass or dig out the soil underneath. Lay down cardboard or several layers of newspaper inside the frame to suppress weeds. This breaks down over time and does not harm the bed. Overlap the pieces so weeds cannot push through the gaps.
Fill the bed with soil. Most gardeners use a mix of topsoil and compost—roughly 60 percent topsoil and 40 percent compost by volume. A 4-by-8-foot bed 12 inches deep holds about 32 cubic feet of soil, which is roughly 1.2 cubic yards. You can buy this bagged or in bulk from a landscape supplier.
Do not use garden soil from your yard; it compacts and drains poorly in a raised bed. Topsoil and compost are designed to stay loose and hold moisture. Fill the bed to the top, water it thoroughly, and let it settle for a day or two before planting. It will sink 2 to 4 inches as it compacts.
Sizing your bed for your space and needs
The standard raised bed is 4 feet wide, 8 feet long, and 12 inches deep. This size is straightforward to reach from both sides, holds enough soil for most vegetables, and uses standard lumber lengths with no waste.
If you have less space, a 3-by-6-foot or 2-by-4-foot bed works just as well. If you want to grow root vegetables like carrots or potatoes, go 18 inches deep instead of 12. If you are growing only shallow-rooted plants like lettuce or herbs, 8 inches is enough.
Avoid beds wider than 4 feet; you will struggle to reach the center without stepping on the soil. Avoid beds longer than 8 feet unless you plan to build multiple smaller beds instead—a long bed is harder to move and more likely to rack (twist out of square) as the wood settles.
Maintenance and when to replace boards
Cedar boards last 10 to 15 years before they start to rot. You will notice the wood becoming soft or spongy at the base, especially where it touches the soil. When that happens, you can replace just the affected boards without rebuilding the whole bed.
To extend the life of wooden beds, do not stain or seal them. Stain traps moisture and actually speeds rot. Let the wood weather naturally. You can refresh the appearance by power-washing it every few years, but this is optional.
Soil in a raised bed compacts and depletes over time. Add 2 to 4 inches of compost to the top each spring. After five to seven years, you may want to empty the bed, refresh the bottom third with new compost, and refill. This keeps the soil loose and nutrient-rich.
Frequently Asked Questions
Do I need to line the bottom of a raised bed?
No. A solid bottom would trap water and cause rot. Cardboard or newspaper under the soil suppresses weeds for the first year or two, then breaks down harmlessly. After that, weeds are less of a problem because the raised bed soil is loose and straightforward to pull from.
Can I use treated wood if it is newer pressure-treated?
Yes, pressure-treated wood made after 2004 is safe for vegetables. But untreated cedar costs the same and lasts just as long, so there is no reason to choose treated wood. Avoid any pressure-treated wood from before 2004.
How deep does a raised bed need to be?
Twelve inches is standard and works for most vegetables. Root vegetables like carrots, beets, and potatoes need 18 inches. Shallow-rooted plants like lettuce, herbs, and spinach need only 8 inches. If you are unsure, 12 inches is a safe middle ground.
What if my yard is not level?
A slight slope is fine and helps with drainage. If the slope is steep, you can dig out the high side slightly and build up the low side with soil before placing the bed. The goal is to keep the bed itself reasonably level so soil does not wash to one end when you water.
How much does it cost to build a raised bed?
A 4-by-8-foot cedar bed costs $50 to $100 for boards and fasteners, plus $40 to $80 for soil, depending on whether you buy bagged or bulk. Composite beds cost $100 to $150 for materials. Pre-assembled kits range from $100 to $300 depending on size and material.