What you need to build a raised bed
A raised bed is a wooden or composite box you fill with soil and plant into. To build one, you need four boards (usually cedar or composite), four corner brackets or screws, a drill or screwdriver, a level, and a tape measure. Most people also add landscape fabric to the bottom to block weeds. That is the entire list.
The most common size is 4 feet by 8 feet by 12 inches deep, which fits two standard garden rows and costs between $80 and $200 in materials depending on wood choice. Smaller beds (3 by 6 feet or 4 by 4 feet) cost less and are easier to reach into. Deeper beds (18 inches) cost more but let you grow root vegetables like carrots and parsnips.
Cedar lasts 10 to 15 years before rot sets in. Composite boards (wood fibre mixed with plastic) cost more upfront but last 20 years or longer and do not need sealing. Treated lumber is cheaper but contains chemicals and is not recommended for vegetable gardens where the chemicals can leach into soil.
Key Takeaways
- A basic raised bed needs four boards, corner brackets, a drill, a level, and landscape fabric — you can assemble one in two to three hours.
- Cedar boards last 10 to 15 years; composite boards cost more but last 20 years and require no maintenance.
- The standard 4-by-8-foot size costs $80 to $200 and fits most home gardens; smaller beds are easier to maintain.
- Level the ground before assembly so water drains evenly and the bed sits stable.
- Fill with a mix of topsoil and compost rather than garden soil alone, which compacts over time.
Prepare the ground and choose your location
Pick a spot that gets at least six hours of direct sun per day. Most vegetables need this much light to produce well. If your yard is shaded, choose a location that gets morning sun — afternoon shade in hot climates actually helps lettuce and spinach stay tender.
Clear the ground of grass and weeds. You can remove the sod by hand with a spade, or lay cardboard over the area and let it kill the grass underneath over two to four weeks. Cardboard is slower but requires less work. Once the ground is clear, use a level to check if it slopes. If it slopes more than an inch or two, either level it by moving soil or accept that water will drain toward the low end.
Lay landscape fabric on the bare ground before you place the bed frame. This blocks weeds from growing up through the bottom. Cardboard works too and breaks down over time, but fabric lasts longer. Overlap the edges by six inches so weeds cannot creep in at the seams.
Assemble the frame and check it for square
Lay your four boards on the ground in a rectangle. If you are using corner brackets, attach them to the inside corners with screws — use at least three screws per bracket. If you are using screws alone, drill pilot holes first (a small hole that guides the screw and prevents the wood from splitting), then drive two screws through each corner board into the end of the adjacent board.
Once the frame is screwed together, place it on the fabric-covered ground. Use a level to check that the top edges are even side to side and front to back. If one corner is higher, you can shim it with a shingle or small stone underneath, or dig out soil from the high side. The goal is level enough that water does not pool in one corner.
If the frame is not square (corners not at 90 degrees), measure diagonally from corner to corner. Both diagonals should be the same length. If they are not, loosen the screws slightly and push the frame until the diagonals match, then tighten again.
Fill the bed with soil and compost
A 4-by-8-foot bed that is 12 inches deep holds about 32 cubic feet of soil. That is roughly 1.2 cubic yards. You can buy this as bagged soil (about 40 bags of 2 cubic feet each) or have it delivered in bulk. Bulk is cheaper per cubic foot but requires a truck.
Do not use garden soil alone — it compacts and becomes hard to work. Instead, mix topsoil with compost in a ratio of about two parts topsoil to one part compost. This gives you good drainage, nutrients, and structure. If you are starting in spring and want to plant right away, fill completely with this mix. If you are building in fall, you can fill partially and let it settle over winter, then top it off in spring.
Spread the soil evenly and rake it level. Water it lightly to help it settle. It will drop an inch or two over the first few weeks as it compacts naturally — this is normal.
Add edging and pathways if you are building multiple beds
If you are building more than one bed, space them at least two feet apart so you can walk and kneel between them. You can lay cardboard or landscape fabric between beds to block weeds, or spread wood chips or straw for a softer walking surface. Wood chips break down over time and add organic matter to the soil, so you will need to refresh them every year or two.
Some gardeners add a border of metal or plastic edging around the outside of the beds to keep grass from creeping in. This is optional but makes maintenance easier. Edging costs $10 to $30 per bed.
Plant and maintain your bed
Once the soil is in place and settled, you can plant when ready. Space plants according to the seed packet or transplant label — raised beds warm up faster than ground soil, so you can plant a week or two earlier in spring. Water regularly; raised beds dry out faster than in-ground gardens because they have more surface area exposed to sun and wind.
Each year, add two to three inches of compost to the top of the bed. This replaces nutrients that plants take out and keeps the soil structure loose. After three to five years, you may need to replace the entire soil if it has become compacted or depleted, though adding compost regularly delays this.
Cedar boards will eventually rot at the bottom where they touch wet soil. You can extend their life by painting the inside with a wood sealant before filling, or straightforward plan to replace the boards when they fail. Composite boards do not rot and need no maintenance beyond occasional cleaning.
Common mistakes to avoid
The most common mistake is building the bed on top of existing grass without removing it first. The grass does not die; it grows up through the soil and competes with your plants. Remove it or kill it with cardboard before you build.
The second mistake is filling with garden soil alone. It compacts into a hard, airless mass that roots cannot penetrate and water cannot drain through. Always mix in compost.
The third is building in a shaded spot and expecting sun-loving vegetables to thrive. Tomatoes, peppers, and squash need six hours of direct sun. Lettuce and spinach tolerate partial shade, but most other vegetables do not.
Finally, do not skimp on the depth if you want to grow root vegetables. Carrots, beets, and parsnips need at least 12 inches; 18 inches is better. Shallow beds work fine for lettuce, herbs, and shallow-rooted crops like bush beans.
Frequently Asked Questions
Can I build a raised bed on concrete or a patio?
Yes, but you need to drill drainage holes in the bottom or line it with landscape fabric with gaps for water to escape. Without drainage, water pools and roots rot. You will also need to water more often because the concrete does not absorb moisture the way soil does.
How long does it take to build a raised bed?
Assembly takes one to two hours for a single bed if you have a drill and the boards are pre-cut. Preparing the ground (removing grass, laying fabric, leveling) takes another one to two hours. Filling with soil takes 30 minutes to an hour depending on whether you are using bags or bulk delivery.
What wood should I use if cedar is too expensive?
Composite boards last longer than cedar and cost $30 to $50 more per bed upfront, but they do not rot and require no sealing. If budget is tight, untreated pine or fir works but lasts only five to seven years. Avoid treated lumber for vegetable gardens.
Do I need to add a bottom to the raised bed?
No. An open bottom lets roots grow deeper and water drain away. A solid bottom (wood or plastic) prevents this and can cause waterlogging. Landscape fabric on the ground is enough to block weeds.
Can I use old wood or reclaimed materials?
Yes, as long as it is not treated with chemicals or contaminated. Untreated barn wood, old fence boards, and reclaimed cedar all work. Avoid wood from old railroad ties, which contain creosote, or anything that was painted or stained with unknown products.