Build a raised bed by stacking untreated wood boards, securing the corners, and filling with soil
A raised bed is a wooden or composite frame sitting on top of your existing ground, filled with soil for planting. The simplest version uses four boards screwed or nailed together at the corners, set in place, and filled. You do not need a foundation, concrete, or special tools—just boards, fasteners, a drill or hammer, and soil. Most people finish one in an afternoon.
The most common size is 4 feet by 8 feet by 12 inches deep, which fits standard garden layouts and gives you enough room to plant multiple rows. You can make yours smaller or larger depending on your space and how much you want to fill. Depth matters more than you might think: 12 inches works for shallow-rooted plants like lettuce and herbs, but root vegetables and tomatoes need at least 18 inches.
Key Takeaways
- Use untreated wood boards (cedar, redwood, or pine) at least 2 inches thick, never pressure-treated lumber, which can leach chemicals into soil.
- find corners with galvanized screws or nails so the frame stays square and does not bow outward as soil weight builds.
- You can place a raised bed directly on grass or soil without removing the sod first, though removing it makes setup easier.
- Fill your bed with a mix of topsoil, compost, and peat moss or coconut coir rather than garden soil alone, which compacts over time.
- Cedar and redwood last 10 to 15 years; pine lasts 5 to 10 years; composite materials last 20+ years but cost more upfront.
Choose your wood and cut it to length
Untreated wood is the safest choice for food gardens. Cedar and redwood naturally resist rot and insects, so they last longer than pine without chemical treatment. Pine is cheaper and works fine if you are willing to replace it in 5 to 10 years. Never use pressure-treated lumber—the chemicals used to preserve it can leach into soil and accumulate in plants you eat.
Buy boards that are at least 2 inches thick (often labeled 2x10 or 2x12 at the lumber yard). Thinner boards will bow and warp as soil weight pushes outward. A 4-by-8-foot bed needs two 8-foot boards and two 4-foot boards. If you want a different size, measure your space first and write down the length and width you need, then ask the lumber yard to cut boards to those lengths—most will do this for free or a small fee.
Assemble the frame at ground level
Lay all four boards on flat ground in a rectangle shape. At each corner, drill two pilot holes (small starter holes that guide the screw) through one board and partway into the end of the other board. Use a drill bit slightly smaller than your screw diameter so the screw grips without splitting the wood.
Drive a 3-inch galvanized deck screw through each pilot hole. Galvanized screws resist rust better than regular steel. Tighten them firmly so the corner is snug, but do not over-tighten—you want the boards flush and square, not crushed. If you do not have a drill, you can use a hammer and galvanized nails (three per corner, staggered), though screws hold better over time.
Check that the frame is square by measuring corner to corner diagonally. Both diagonal measurements should be the same length. If they are not, gently push the longer diagonal until the measurements match.
Position the frame and level the ground
Drag or carry the assembled frame to your chosen spot. You can place it directly on grass, soil, or pavement—you do not need to remove sod first, though doing so makes the bed sit more evenly. If you leave grass underneath, it will eventually break down and add organic matter to your soil.
Use a level tool to check that the frame is not tilted. Place the level along the length of each side. If one corner is higher than the others, you have two options: dig out soil under the high corner to lower it, or add soil under the low corners to raise them. Most people find it faster to add soil under low spots. Aim for level within about half an inch—perfect level is not necessary, but a very tilted bed will have shallow soil on one end and deep soil on the other.
Fill the bed with soil and amendments
Do not fill with garden soil alone. Garden soil compacts heavily once it is wet and settled, leaving little room for roots and water. Instead, use a mix: roughly 40 percent topsoil, 40 percent compost, and 20 percent peat moss or coconut coir. This blend drains well, holds moisture, and gives roots room to grow.
Calculate how much you need by multiplying length × width × depth (in feet), then dividing by 27 to get cubic yards. A 4-by-8-foot bed that is 1 foot deep needs about 1.2 cubic yards. Most garden centers sell soil and compost by the bag or cubic yard. Buying by the yard is cheaper if you have a way to haul it, but bags are easier to handle if you are working alone.
Dump the soil and amendments into the bed and mix them together with a shovel or garden fork. Water the mix lightly as you go—this helps the ingredients blend and settles the soil. The bed will sink a few inches over the first week as everything settles, so fill it slightly higher than the rim if you want it full later.
Common mistakes to avoid
Using pressure-treated wood is the most serious mistake. The preservatives are designed to stay in the wood, but they can still leach into soil, especially in wet climates or if you are growing food. Untreated cedar or redwood costs a bit more but is worth it for peace of mind.
Boards that are too thin will bow outward as soil weight builds, especially in the middle of long sides. A 2-inch board is the minimum; 2x12 is better if your budget allows. If you already have thin boards, you can reinforce them by driving a stake (a 2x2 post) into the ground outside the bed and screwing the board to the stake.
Filling with only garden soil leads to compaction and poor drainage. The compost and peat moss are not optional—they keep the soil light and workable year after year. If cost is tight, start with the 40-40-20 mix and add more compost next spring.
Skipping the level check means one end of your bed will have much less soil depth than the other. Spend five minutes with a level at the start; it saves frustration later.
Maintain your raised bed over time
Every spring, add 1 to 2 inches of compost on top and work it into the top few inches of soil. This replaces organic matter that breaks down over the year and keeps the soil rich. You do not need to replace the entire bed—just refresh the top layer.
Check the wood frame each year for rot, especially at the corners and where it touches soil. Cedar and redwood rot slowly, but pine can soften in 5 to 7 years. If you see soft spots, you can cut out the damaged section and screw in a new board, or replace the whole frame when it fails.
If the soil level drops noticeably, add more soil and compost. Settling is normal, especially in the first year. Do not worry about the bed sinking—just keep it topped up so you have the depth you need for your plants.
Frequently Asked Questions
Do I have to remove the grass before I put down a raised bed?
No. Grass underneath will eventually break down and add organic matter. If you leave it, the bed will settle more in the first year as the grass decomposes. If you want the bed level when ready, remove the sod with a shovel first—it takes 20 to 30 minutes for a 4-by-8 bed.
What is the best wood for a raised bed?
Cedar and redwood last 10 to 15 years and resist rot naturally. Pine is cheaper but lasts only 5 to 10 years. Composite materials (plastic and wood fiber) last 20+ years but cost two to three times as much. For food gardens, avoid pressure-treated wood entirely.
How deep does a raised bed need to be?
Twelve inches works for lettuce, herbs, and shallow-rooted greens. Root vegetables like carrots and beets need 12 to 18 inches. Tomatoes and peppers need at least 18 inches. If you are growing a mix, build it 18 inches deep so everything has room.
Can I put a raised bed on concrete or pavement?
Yes. The bed will sit on top and drain through the bottom into the concrete or soil below. You may need to water more often since water cannot drain as easily, but it works fine. Make sure the concrete is not treated with chemicals that could leach into soil.
How much does it cost to build a raised bed?
A 4-by-8-foot cedar bed costs roughly $80 to $150 for wood and fasteners, plus $40 to $100 for soil and compost depending on whether you buy by the bag or cubic yard. Pine is cheaper ($40 to $80 for wood). Composite materials run $200 to $400 for the frame alone.