Build a basic raised bed in a weekend with wood, screws, and a drill

A raised garden box is a four-sided wooden frame that sits on top of your soil. You build it by cutting lumber to length, drilling pilot holes, and fastening the corners together with exterior-grade screws. The whole project takes four to six hours for a standard 4-by-8-foot bed, and you need only a tape measure, saw, drill, and level. No special skills required — just straight cuts and tight corners.

The most common size is 4 feet wide by 8 feet long by 12 inches deep, which holds about 32 cubic feet of soil and fits through most garden gates. You can build smaller (2 by 4 feet) or larger (6 by 12 feet), but wider than 4 feet means you cannot reach the center from either side without stepping into the bed.

Key Takeaways

  • Use untreated cedar or composite lumber rated for ground contact; pressure-treated wood from before 2004 contains arsenic and should not touch soil where you grow food.
  • Cut four boards to length, drill pilot holes at each corner to prevent splitting, and fasten with 3-inch exterior-grade screws — two screws per corner, driven from the outside in.
  • Assemble the frame on level ground and check all four corners with a carpenter's square before tightening the final screws.
  • A 4-by-8-foot bed 12 inches deep requires about 32 cubic feet of soil, which costs between $30 and $60 depending on soil quality and your location.

Choose lumber that will not rot or leach chemicals

Cedar is the most popular choice because it resists rot naturally and lasts 10 to 15 years in the ground. A 4-by-8-foot bed built from cedar 2-by-12 boards costs roughly $80 to $120 for lumber alone. Cedar is lightweight, straightforward to cut, and does not require treatment.

Composite lumber (plastic and wood fiber mixed) lasts 20 to 30 years and never rots, but costs two to three times more than cedar and is heavier to move. It does not splinter and requires no maintenance, so it is worth the price if you plan to keep the bed for decades.

Avoid pressure-treated lumber manufactured before 2004, which contains chromated copper arsenate (CCA) — a pesticide that leaches into soil. Lumber treated after 2004 uses copper-based preservatives that are safer, but cedar and composite are still the better choice for vegetable beds. Never use railroad ties, which are soaked in creosote, a carcinogenic coal tar.

Cut the boards and prepare the corners

Measure and mark your four boards to length. For a 4-by-8-foot bed, cut two boards 8 feet long and two boards 4 feet long. Use a circular saw or hand saw, and cut straight — a crooked cut will leave gaps at the corners. Sand the cut ends lightly to remove splinters, especially if you are using cedar.

Lay the four boards on a flat surface in the shape of a rectangle. Measure the diagonals (corner to opposite corner) — both should be equal. If they are not, the frame is out of square. Adjust the boards until the diagonals match, then mark where the corners will be.

Drill two pilot holes at each corner, about 1.5 inches from the edge and 2 inches apart vertically. Pilot holes prevent the wood from splitting when you drive the screw. Use a drill bit slightly smaller than your screw diameter — for a 3-inch exterior screw, use a 1/8-inch bit.

Fasten the corners with exterior-grade screws

Use 3-inch exterior-grade deck screws or construction screws, not drywall screws or interior wood screws. Exterior screws have a coating that resists rust, and the 3-inch length is long enough to pass through a 2-by-12 board and bite into the adjoining board. Buy screws rated for pressure-treated or cedar wood — the coating matters.

Drive two screws at each corner, from the outside of the frame into the end grain of the adjoining board. Tighten them firmly but do not over-drive — if the screw head sinks below the surface, it will not hold as well. A power drill with a screw-driving bit makes this faster and more consistent than a hand screwdriver.

Check each corner with a carpenter's square as you tighten the screws. The corner should be exactly 90 degrees. If it is not, loosen the screws slightly, adjust the boards, and retighten. Once all four corners are square and tight, the frame is complete.

Level the ground and position the frame

Choose a spot that gets at least six hours of direct sun per day. Clear away grass, weeds, and debris. Use a long level (a 4-foot level is ideal) to check whether the ground is flat. If it slopes, you have two options: level the ground by digging out the high spots and filling the low spots, or build the frame and let it settle unevenly — most gardeners accept a slight slope.

Set the frame in place and check it with the level in two directions — along the length and across the width. If one corner is high, you can dig out soil beneath it or place shims (thin wood wedges) under the frame to level it. The frame does not need to be perfectly level, but a slope greater than 1 inch over 8 feet will cause water to pool on one side.

Once the frame is positioned, you can add landscape fabric to the bottom to block weeds, though it is not required. Staple the fabric to the inside of the frame, leaving the corners loose so water can drain.

Fill the bed with soil and let it settle

A 4-by-8-foot bed 12 inches deep holds about 32 cubic feet of soil. You can buy bagged soil (convenient but expensive), bulk soil delivered by truck (cheaper for large quantities), or a mix of topsoil and compost from a local supplier. Most gardeners use a blend of 60 percent topsoil and 40 percent compost for the best balance of drainage and nutrients.

Dump the soil into the frame and spread it evenly with a rake. The soil will settle over the first few weeks as it absorbs water and compacts. Do not plant when ready — wait three to five days and add more soil if needed to bring it back to the top of the frame. This settling is normal and does not mean the frame is failing.

Water the soil thoroughly after filling. This helps it settle and reveals any low spots. Add more soil to bring the level back up if needed.

Common mistakes to avoid

Using the wrong lumber: Pressure-treated wood from before 2004 or railroad ties will contaminate your soil. Cedar and composite are the safe choices.

Skipping pilot holes: Driving screws without pilot holes splits the wood, especially near the ends of boards. The split weakens the corner and the frame may rack (twist out of square) over time.

Mixing screw types: Interior screws rust quickly in soil. Use exterior-grade screws rated for the lumber type you chose.

Building on uneven ground: A frame that rocks will shift as the soil settles, opening gaps at the corners. Spend time leveling the ground or shimming the frame before you fill it.

Filling before the frame is square: Once the frame is full of soil, it is hard to adjust. Check that all four corners are 90 degrees and the diagonals are equal before you add soil.

Frequently Asked Questions

How deep should a raised bed be?

Twelve inches is the minimum for most vegetables — enough for lettuce, spinach, and shallow-rooted herbs. Root vegetables like carrots and potatoes need 12 to 18 inches. If you are growing in clay soil, go deeper (18 inches) because the raised bed soil will not mix with the clay below. Shallow beds (6 to 8 inches) work for microgreens and some herbs, but limit your options.

Can I build a raised bed without screws?

Yes, but it is not ideal. You can nail the corners with 3-inch galvanized nails, but nails are more likely to loosen as the wood settles and the soil shifts. Screws hold tighter and longer. You can also buy metal corner brackets and bolt the frame together, which is stronger but more expensive and slower to assemble.

How long does a cedar raised bed last?

Cedar typically lasts 10 to 15 years in the ground before the wood begins to rot at the base. You can extend its life by painting or staining the exterior (not the interior, where it touches soil), or by replacing the bottom boards when they rot while keeping the sides intact. Composite beds last 20 to 30 years with no maintenance.

Do I need to line the bottom of the bed?

Landscape fabric blocks weeds from growing up through the bottom, which is helpful if you are building on grass or weeds. It is not required if you are building on bare soil or pavement. Do not use plastic sheeting — it traps water and prevents drainage. Landscape fabric allows water through while blocking weeds.

What size raised bed should I build?

A 4-by-8-foot bed is the standard because it is straightforward to reach the center from either side and fits through most gates. A 2-by-4-foot bed is good for a small space or a beginner. Avoid beds wider than 4 feet unless you plan to step into them — you will not be able to reach the center without compacting the soil. Length does not matter as much, but 8 feet is easier to manage than 12 or 16 feet.