Build your raised bed in four main steps: choose a location, assemble the frame, fill it with soil, and plant
A raised garden bed is a wooden or composite box you build on top of the ground and fill with soil. You build it yourself using boards, corner supports, and basic tools—no digging into existing ground required. Most people can complete a basic 4-by-8-foot bed in two to three hours, and you do not need carpentry experience to do it well.
The real work is gathering materials and deciding where to put it. Once you have chosen a spot that gets sunlight and is reasonably level, the actual assembly is straightforward: cut or buy pre-cut boards, attach them at the corners, set it in place, and fill it. The most common mistake is skipping the level check—a bed that tilts will drain unevenly and make watering harder.
Key Takeaways
- Choose a location that gets at least six hours of direct sunlight and is as level as possible to prevent water from pooling on one side.
- Use untreated wood boards (cedar, redwood, or pine), composite lumber, or galvanized metal—never pressure-treated wood, which can leach chemicals into soil.
- Assemble the frame on the ground first, then move it into place and check that it sits level before filling with soil.
- Fill the bed with a mix of topsoil and compost rather than garden soil alone, which compacts over time and drains poorly.
- A standard bed is 4 feet wide, 8 feet long, and 12 inches deep, though you can adjust dimensions to fit your space and budget.
Choosing the right location and checking the ground
Pick a spot that receives at least six hours of direct sunlight per day if you plan to grow vegetables or herbs. If you want to grow shade-tolerant plants like lettuce or spinach in summer, four to six hours works. Avoid areas directly under trees or beside buildings that block morning sun.
Check that the ground is reasonably level by laying a straight board across the area and placing a level on top of it. If one end is more than an inch higher than the other, you have two choices: dig out the high side slightly, or accept that water will drain toward the low side and water more often on the high side. Most people choose to dig a little rather than fight gravity all season.
Clear away grass, weeds, and debris from the spot where the bed will sit. You do not need to remove the sod completely—the wood will suppress it—but pull out any large roots or rocks that would prevent the frame from sitting flat.
Selecting materials and cutting boards to size
The most durable choice is cedar or redwood, which naturally resist rot and last eight to twelve years. Pine is cheaper and works fine for four to six years before the bottom boards start to rot. Avoid pressure-treated wood—the chemicals used to preserve it can leach into your soil over time.
For a standard 4-by-8-foot bed that is 12 inches deep, you need four boards: two that are 8 feet long and two that are 4 feet long, all cut from 2-by-12 lumber (which is actually 1.5 inches thick and 11.25 inches tall). If you do not have a saw, most lumber yards will make two or three cuts for free when you buy the wood. If you want a deeper bed for root vegetables, use 2-by-14 or 2-by-16 boards instead.
Composite lumber (wood-plastic blend) costs more but lasts twenty years or longer and requires no maintenance. Galvanized metal or steel raised beds are also durable, though they heat up faster in summer and can be harder to assemble without the right fasteners.
Assembling the frame with corner supports
Lay the four boards on a flat surface in a rectangle. At each corner, you need something to hold the boards together—the simplest method is a wooden post or block. Cut four pieces of 4-by-4 lumber to 12 inches long (or whatever height your bed will be). Position one post at each corner on the inside of the rectangle, so the boards rest against it on two sides.
Drill pilot holes through each board into the post to prevent the wood from splitting, then drive 3-inch exterior-grade screws through the board into the post. Use at least two screws per corner—one near the top and one near the bottom. Do not use nails; screws hold much better and are easier to remove if you need to adjust the frame later.
Once all four corners are fastened, flip the frame over and check that all corners are square by measuring diagonally from corner to corner. Both diagonal measurements should be equal. If they are not, push gently on the longer diagonal until the measurements match.
Positioning the bed and checking for level
Move the assembled frame to your prepared location. This is easier with two people, and it is much harder to move once the bed is full of soil, so get it right the first time. Set it down and place a level across the width and length to check that it sits flat. If it rocks, identify which corner is high and either dig out soil beneath that corner or add soil under the low corners.
Once the frame is level, you can add a barrier to the bottom if you want to prevent weeds from growing up through the bed. Landscape fabric or cardboard works—lay it flat inside the frame before you add soil. This step is optional; many gardeners skip it and straightforward pull weeds as they appear.
Filling the bed with soil and compost
Do not use garden soil alone—it compacts and drains poorly. Instead, mix topsoil and compost in roughly equal parts. For a 4-by-8-foot bed that is 12 inches deep, you need about 32 cubic feet of soil, which is roughly 1.2 cubic yards. A cubic yard of topsoil weighs about 1,400 pounds, so order 1.5 cubic yards total (topsoil and compost combined) to account for settling.
Spread the soil and compost in layers, mixing as you go. Fill until the bed is about an inch below the top of the boards—this leaves room for mulch and prevents soil from washing out when you water. Water the bed thoroughly after filling; the soil will settle over the next few days, and you may need to add more to bring it back to the right level.
Planting and maintaining your new bed
Wait a few days after filling before planting to let the soil settle. If you are planting seeds, follow the spacing and depth on the seed packet. If you are transplanting seedlings, dig a hole slightly larger than the root ball, set the plant in, and firm the soil around it.
Water gently after planting and keep the soil consistently moist (not soggy) for the first two weeks while plants establish roots. Add a 2-inch layer of mulch—wood chips, straw, or shredded leaves—around plants to retain moisture and suppress weeds. Avoid piling mulch directly against plant stems, which can cause rot.
Each year, add 1 to 2 inches of compost to the top of the bed to replace nutrients that plants have used. This keeps the soil rich and maintains the level as the original soil settles.
Frequently Asked Questions
Can I build a raised bed on top of grass without removing it first?
Yes. The wood will suppress the grass underneath, and it will eventually decompose and become part of your soil. You may see some grass poking through the edges for the first season, but pulling it out is easier than removing all the sod beforehand. If you want faster results, lay cardboard or landscape fabric on the grass before setting the frame in place.
What size should my raised bed be?
A 4-by-8-foot bed is standard because it is wide enough to reach the center from either side (4 feet) without stepping in, and 8 feet is a common board length. If you have less space, a 3-by-6-foot or 2-by-4-foot bed works just as well. Make the width no more than 4 feet so you can reach the middle without stepping on the soil.
Do I need to line the bottom of the bed?
No, but a cardboard or landscape fabric barrier slows weed growth from below. If you skip it, you will pull more weeds the first season but fewer in later years as the soil deepens. Either approach works; it is a matter of preference and how much time you want to spend weeding.
How deep should a raised bed be?
Twelve inches is the minimum for most vegetables and herbs. Root vegetables like carrots and parsnips need at least 12 inches, and deeper is better—18 inches allows you to grow almost anything. Shallow beds (6 to 8 inches) work for lettuce, spinach, and other greens but limit your options.
Can I use treated wood for my raised bed?
Modern pressure-treated wood is safer than older versions, but untreated cedar, redwood, or composite lumber is still the better choice for a vegetable garden. Treated wood is designed for decks and fences where leaching into soil is not a concern. For food production, stick with untreated wood or composite.