What You Need to Build a Raised Bed
A raised 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. The simplest version uses four boards, four corner posts, a level, a drill, and wood screws — no concrete, no digging, no special skills required.
Most people use untreated cedar, composite lumber, or galvanized metal. Cedar lasts 10 to 15 years outdoors without treatment. Composite boards (made from wood fibers and plastic) last longer but cost more. Avoid pressure-treated wood if you are growing vegetables, because the chemicals can leach into soil over time.
A standard raised bed is 4 feet long, 2 feet wide, and 12 inches deep. This size fits in most yards, holds enough soil for vegetables or flowers, and is straightforward to reach from both sides. You can make it larger or smaller depending on your space and what you want to grow.
Key Takeaways
- Cedar or composite boards last longest outdoors; avoid pressure-treated wood for vegetable gardens.
- A 4-by-2-foot bed with 12-inch depth is the standard size and works for most gardens.
- You need a level surface, corner posts, wood screws, and a drill — no concrete or digging required.
- Assembly takes two to four hours and requires only basic tools you may already own.
- Fill the bed with a mix of topsoil and compost, not garden soil alone, for best results.
Choosing Your Location and Preparing the Ground
Pick a spot that gets at least six hours of direct sun if you are growing vegetables. If you are growing shade-tolerant plants like lettuce or herbs, four to five hours works. Avoid areas under tree branches or next to buildings that block light.
The ground does not have to be perfectly level, but it should be reasonably flat. If your yard slopes, you can build the bed on the slope — just make sure the top of the bed is level once it is assembled. Use a level to check this before you fill it with soil.
Clear away grass, weeds, and debris from the footprint of the bed. You do not have to remove the sod underneath — it will break down over time. If you want faster results, you can lay cardboard or newspaper under the bed to kill the grass faster, but it is not necessary.
Cutting and Assembling the Frame
Cut your boards to length. For a 4-by-2-foot bed, you need two boards 4 feet long and two boards 2 feet long. If you do not have a saw, most lumber yards will cut boards for free or for a small fee when you buy them.
Cut four corner posts from 4-by-4 lumber, each 18 inches long. These posts will sit at the corners and hold the boards together. The posts stick 6 inches above the boards and 12 inches into the ground, which keeps the frame stable and prevents the boards from bowing outward.
Lay the boards and posts on a flat surface and assemble them in a rectangle. Position each post at a corner so the boards sit flush against the inside face of the post. Drill two pilot holes through each board into each post, then drive 3-inch wood screws through the holes. Use at least two screws per connection — four is better if you have the time.
Check that the frame is square by measuring diagonally from corner to corner. Both measurements should be the same. If they are not, adjust the frame until they match, then tighten all screws.
Setting the Frame in Place and Leveling
Carry the assembled frame to your chosen location and set it down. Use a level to check that the top edges are level in both directions — front to back and side to side. If the ground is uneven, you can dig out high spots or add soil under low spots until the frame sits level.
Once the frame is level, you can drive the corner posts into the ground if your soil is soft enough. Use a mallet or the end of a sledgehammer to tap the posts down. Stop when the bottom of the boards sits on the ground or just barely above it. If your soil is hard or rocky, you may not be able to drive the posts in — that is fine. The frame will still work as long as it is level.
Check the level again after the posts are driven in. Make small adjustments if needed. Once you are satisfied, the frame is ready for soil.
Filling the Bed With Soil
Do not use garden soil alone. Garden soil is heavy, compacts easily, and does not drain well in a raised bed. Instead, use a mix of topsoil and compost. A common recipe is half topsoil and half compost by volume.
For a 4-by-2-foot bed that is 12 inches deep, you need about 8 cubic feet of soil mix. That is roughly 16 bags of bagged soil if you are buying it, or you can order bulk soil from a landscape supplier and have it delivered. Bulk soil is cheaper if you need a lot, but bagged soil works fine for a single bed.
Fill the bed gradually and water as you go. This helps the soil settle and removes air pockets. After a week or two, the soil will settle further, and you may need to add more. Top it off until it is about an inch below the rim of the frame.
Tools and Materials Checklist
| Item | Quantity | Notes |
|---|---|---|
| Cedar or composite boards (2×12) | 2 at 4 feet, 2 at 2 feet | Untreated cedar lasts 10–15 years; composite lasts longer |
| 4×4 corner posts | 4 posts, 18 inches each | Cedar or composite; same material as boards |
| 3-inch wood screws | 16 to 24 screws | Stainless steel or coated; 2–4 per corner |
| Topsoil and compost mix | 8 cubic feet | Half topsoil, half compost; about 16 bags |
| Drill with bits | 1 | For pilot holes; prevents wood splitting |
| Level | 1 | 2 to 4 feet long; check both directions |
| Saw (optional) | 1 | Lumber yard can cut boards for you |
| Mallet or sledgehammer | 1 | For driving corner posts into ground |
Common Mistakes to Avoid
Do not use pressure-treated wood for vegetable beds. The chemicals used to preserve the wood can leach into soil and be absorbed by plants. Cedar and composite are safer choices. If you already have a pressure-treated bed, you can line the inside with landscape fabric to reduce contact between soil and wood.
Do not skip the corner posts. Boards alone will bow outward under the weight of soil and water. Posts keep the frame square and stable for years. If you are building a very large bed (more than 6 feet long), use additional posts in the middle of the long sides.
Do not use garden soil straight from a bag. It compacts and drains poorly in a raised bed. Mix it with compost to improve drainage and add nutrients. The bed will settle over the first month, so fill it slightly higher than you think you need.
Frequently Asked Questions
How deep does a raised bed need to be?
Twelve inches is the minimum for most vegetables and flowers. Root vegetables like carrots and beets need at least 12 inches; shallow-rooted plants like lettuce and herbs can grow in 8 inches. If you are growing perennials or shrubs, 18 inches is better. Deeper beds also hold more moisture and stay cooler in summer.
Can I build a raised bed without corner posts?
Not if you want it to last. Boards alone will bow outward under soil pressure within a season or two. Corner posts are essential. If you do not want to cut posts, you can buy pre-made raised bed kits that include corner brackets instead of posts — they work the same way.
What is the best wood for a raised bed?
Untreated cedar is the most common choice because it resists rot naturally and lasts 10 to 15 years. Composite boards last longer (20+ years) but cost more. Avoid pressure-treated wood for vegetable gardens. Redwood and black locust also resist rot but are harder to find and more expensive than cedar.
How long does it take to build a raised bed?
Assembly usually takes two to four hours, depending on whether you cut the boards yourself or have them cut at the store. Setting it level and filling it with soil adds another hour or two. Most people can finish a single bed in a weekend.
Do I need to line the bottom of the bed?
No. Lining the bottom with landscape fabric or hardware cloth is optional. Fabric can slow drainage and trap moisture; hardware cloth keeps out burrowing pests like moles and voles. If you have a pest problem, hardware cloth is worth the extra cost. Otherwise, the bed works fine without a liner.