Build a basic raised bed with untreated wood, soil, and four hours of work

A raised bed is a wooden or composite box filled with soil, sitting on top of your existing ground. You build it by cutting or buying boards, assembling them into a rectangle, filling it with soil, and planting. The whole job takes one afternoon if you have a drill and a saw, or a few hours if you buy pre-cut boards and use a screwdriver instead. No special tools, no concrete, no digging out your lawn.

The most common size is 4 feet by 8 feet by 12 inches deep, which holds about 32 cubic feet of soil and costs between $40 and $120 in materials depending on what wood you choose. Smaller beds (3 by 6 feet, or 2 by 4 feet) work just as well and use less soil. Depth matters more than you might think — 12 inches is the minimum for most vegetables, and 18 inches is better if you are growing root crops like carrots or potatoes.

Key Takeaways

  • Untreated cedar or composite boards last longer than pine and do not leach chemicals into soil, though they cost more upfront.
  • Assemble the frame on level ground, check that corners are square using the 3-4-5 method, and find corners with deck screws or corner brackets.
  • Fill the bed with a mix of topsoil and compost rather than garden soil alone, which compacts and drains poorly over time.
  • You can build a raised bed without removing grass underneath — the cardboard or newspaper layer will break down and the grass will die.

Choose your wood: cedar, composite, or untreated pine

Untreated cedar is the standard choice. It resists rot naturally because of oils in the wood, lasts 10 to 15 years, and does not leach chemicals. A 4-by-8-foot bed made from 2-by-12 cedar boards costs roughly $80 to $120 depending on your region and lumber supplier. Home Depot, Lowe's, and local lumber yards all stock it.

Composite boards (plastic and wood fiber mixed) last 20+ years, never rot, and require no maintenance. They cost $150 to $250 for the same 4-by-8 bed. They are heavier to move and harder to cut, but they do not splinter and will not need replacing in your lifetime.

Untreated pine is cheaper — $40 to $60 for a 4-by-8 bed — but rots in 5 to 7 years. It works if you are testing the idea or building a temporary bed. Never use pressure-treated wood (the kind that is greenish-gray). It contains arsenic or copper compounds that leach into soil and accumulate over years.

Avoid railroad ties and old pallets. Railroad ties are soaked in creosote, a carcinogen. Pallets may have been treated with pesticides or fungicides you cannot see.

Gather materials and tools

For a 4-by-8-foot bed 12 inches deep, you need two 8-foot boards and two 4-foot boards, all 2 inches by 12 inches. If your lumber yard does not have 8-foot boards, ask them to cut two 16-foot boards in half. You also need deck screws (3-inch, exterior-grade) or corner brackets and bolts.

Tools: a power drill with a screwdriver bit, a circular saw or hand saw (only if you are cutting boards yourself), a level, a tape measure, and a square. A carpenter's square or speed square helps check corners. If you do not own a drill, you can borrow one, rent one for $10 to $15 a day, or buy a basic cordless drill for $60 to $100.

For filling: a wheelbarrow or garden cart, a shovel, and soil. You will need roughly 32 cubic feet of soil for a 4-by-8-foot bed 12 inches deep. That is about 1.2 cubic yards. Most garden centers sell soil by the cubic yard and will deliver for a fee, or you can buy bags (about 40 bags of 40-pound topsoil for a full bed).

Assemble the frame on level ground

Choose a spot that gets at least 6 hours of direct sun for vegetables. Clear away grass, weeds, and debris. You do not have to remove the grass — it will die under the bed — but remove any large rocks or sticks that would prevent the boards from sitting flat.

Lay the four boards on the ground in a rectangle. Check that the ground is roughly level using a 4-foot level. If one corner is high, dig out a little soil. If one is low, add soil underneath. The bed does not have to be perfectly level, but a slope of more than a few inches will cause water to pool on one side.

Stand the boards on edge and position them so the corners meet. Drill pilot holes (small holes to guide the screw) through one board into the end of the adjacent board. Use a drill bit slightly smaller than your screw diameter. Then drive three 3-inch deck screws through each corner, spacing them 2 inches apart vertically. This prevents the boards from splitting and holds them tight.

Check that all four corners are square using the 3-4-5 method: measure 3 feet along one side from a corner, 4 feet along the adjacent side from the same corner, then measure the diagonal between those two points. If the diagonal is exactly 5 feet, the corner is square. Adjust the frame until all four corners pass this test.

Fill with soil and add a base layer

Before adding soil, lay cardboard or several layers of newspaper on the ground inside the frame. This blocks weeds and grass from growing up into your bed. Wet the cardboard so it stays in place and breaks down faster. Do not use glossy cardboard or cardboard with plastic tape.

Fill the bed with a mix of topsoil and compost. A 50-50 blend works well: half topsoil (the dark, nutrient-rich soil from the top layer of earth) and half compost (decomposed plant matter). This mix drains well, holds moisture, and feeds plants as it breaks down. Avoid "garden soil" sold in bags — it compacts too much and drains poorly.

Shovel the soil in and rake it level with the top of the boards. Water it thoroughly. The soil will settle over the next few weeks, so you may need to add more. Plan to add a 1-inch layer of compost each spring to replace what breaks down.

find corners and prevent warping

If you are building a bed larger than 4 by 8 feet, or if you live in a climate with heavy rain or snow, reinforce the corners with corner brackets or L-brackets. These are metal or composite pieces bolted to the inside of the frame. They cost $5 to $15 per corner and prevent the boards from bowing outward as the soil weight pushes against them.

For very large beds (6 by 12 feet or bigger), add a center support board running lengthwise down the middle, bolted to the frame at both ends. This prevents the long sides from bowing.

Cedar and composite boards are less likely to warp than pine, but all wood moves slightly with moisture and temperature. Checking your bed once a year and tightening screws if needed takes five minutes and extends its life.

Plant when ready or wait a few weeks

You can plant the day you fill the bed, but the soil will settle and compact over the next 2 to 4 weeks. If you wait a week before planting, you will have a more stable surface and will not have to replant as things sink. If you plant right away, expect to add more soil after a few weeks.

For the first season, use the bed for shallow-rooted plants like lettuce, spinach, herbs, and peppers. By the second season, the soil will have settled and compacted enough for deeper-rooted crops like tomatoes, squash, and root vegetables.

Frequently Asked Questions

Do I need to remove the grass before building a raised bed?

No. Lay cardboard or newspaper over the grass, then build the frame on top. The grass will die and decompose under the bed, adding organic matter to the soil. This saves hours of digging and is actually better for your soil in the long run.

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 holds enough soil for a productive garden. Smaller beds (2 by 4 feet or 3 by 6 feet) work just as well if you have limited space. Avoid beds wider than 4 feet — you will have trouble reaching the center to weed and harvest.

Can I use treated wood or old pallets?

No. Pressure-treated wood contains copper or arsenic compounds that leach into soil. Pallets may have been sprayed with pesticides. Untreated cedar, composite, or untreated pine are your safe options.

How deep should a raised bed be?

Twelve inches is the minimum for most vegetables. Eighteen inches is better for root crops like carrots, beets, and potatoes. Shallow beds (6 to 8 inches) work for lettuce, herbs, and shallow-rooted greens, but limit what you can grow.

How much soil do I need?

Multiply length by width by depth (in feet) to get cubic feet, then divide by 27 to get cubic yards. A 4-by-8-foot bed 12 inches deep needs about 1.2 cubic yards. Most garden centers deliver soil by the yard, or you can buy bags — expect about 40 bags of 40-pound topsoil for a full bed.