Cedar is the best wood choice for a raised bed that will last

Cedar resists rot and insects naturally, so a cedar bed will hold up for 10 to 15 years without treatment or replacement. Other woods — pine, spruce, composite materials — either rot faster, require chemical treatment, or cost more. Cedar costs more upfront than untreated pine, but you buy it once and it outlasts two or three pine beds.

The wood you buy is already milled and ready to assemble. You do not need to fell a tree or mill lumber yourself. A typical 4-by-8-foot bed uses four boards: two 8-foot lengths and two 4-foot lengths, all cut to the same thickness (usually 2 inches nominal, which is actually 1.5 inches). Most garden centers and lumber yards stock cedar in these dimensions.

This guide walks you through measuring your space, buying the right boards, cutting them if needed, and fastening them into a box. The whole job takes two to four hours and requires only basic tools.

Key Takeaways

  • Cedar heartwood resists rot for 10 to 15 years without treatment, making it worth the higher cost compared to pine or untreated softwoods.
  • A standard 4-by-8-foot bed needs four boards (two 8-foot and two 4-foot lengths) cut to the same thickness, available pre-milled at most lumber yards.
  • Fasten the corners with galvanized or stainless steel screws — never nails — because wood movement will loosen nails over time.
  • Level the ground before assembly and check that the frame is square using the 3-4-5 triangle method to prevent water pooling and uneven settling.
  • Line the bottom with hardware cloth if you have gophers or moles, but skip the plastic barrier so water drains and soil breathes.

Measure your space and choose bed dimensions

Decide where the bed will sit. It needs at least six hours of direct sun for most vegetables, and it should be close enough to a water source that you can reach it with a hose. Mark the corners with stakes or spray paint so you can see the footprint on the ground.

Standard sizes are 4 by 8 feet, 4 by 4 feet, or 3 by 6 feet. A 4-by-8 bed is long enough to reach from both sides without stepping into the middle, and it fits two rows of most vegetables. If your space is smaller or oddly shaped, you can build any size — just buy boards long enough to cut to length, or ask the lumber yard to cut them for you (many do this for free or a small fee).

Write down your dimensions. You will need them when you buy wood and when you assemble the frame.

Buy cedar boards and fasteners

Go to a lumber yard or garden center and ask for cedar boards in 2-by-10 or 2-by-12 dimensions (the first number is thickness, the second is height). The 2-by-10 is standard for most home gardens. Cedar comes in lengths of 6, 8, 10, 12, and 16 feet. Buy lengths that match your bed dimensions or that you can cut to length with a saw.

For a 4-by-8 bed, buy two 8-foot boards and two 4-foot boards, all the same width (2-by-10 or 2-by-12). If the yard does not have 4-foot lengths, buy an 8-foot board and cut it in half yourself, or ask them to cut it.

Buy galvanized or stainless steel screws — never nails. Use 3-inch deck screws or exterior-grade wood screws. Nails will loosen as the wood expands and contracts with moisture and temperature. Screws hold tight through that movement. You will need about 12 screws for a standard bed (three per corner, with one screw per board thickness).

If you have gophers or moles, also buy a roll of 1/2-inch hardware cloth (galvanized steel mesh). This goes on the ground under the bed to keep burrowing animals out. Do not buy plastic sheeting — it traps water and suffocates the soil.

Prepare the ground and level the site

Clear the area of grass, weeds, and large rocks. You do not need to remove every stone, but pull out anything bigger than your fist. If the ground is very uneven, use a shovel to scrape high spots down and fill low spots in. The goal is not a perfectly flat yard — the goal is that your finished bed will sit level so water does not pool in one corner.

Lay out your boards on the ground in the shape of your bed. Use a level to check if the ground slopes. If it does, mark the high corner and the low corner. You will adjust when you assemble the frame.

If you are using hardware cloth, unroll it over the prepared ground and cut it to size with wire cutters or tin snips. Overlap the edges by at least 6 inches so animals cannot squeeze through the seams. You can staple it to the ground with landscape staples, but this is optional — the weight of the frame and soil will hold it in place.

Assemble the frame and check for square

Stand the boards on edge in the shape of your bed. Before you fasten anything, check that the corners are square using the 3-4-5 triangle method: measure 3 feet along one side from a corner, measure 4 feet along the adjacent side from the same corner, then measure the diagonal distance between those two marks. If the diagonal is exactly 5 feet, the corner is square. If it is longer or shorter, adjust the boards until it measures 5 feet. Repeat at all four corners.

Once all corners are square, drill a pilot hole at each corner (a small hole that guides the screw and prevents splitting). Drive three 3-inch screws through the end of one board into the end of the adjacent board, spacing them vertically so they do not hit each other. Use a power drill or a hand screwdriver — either works, but a drill is faster.

After you fasten all four corners, place a level on the inside of the frame and check that it is level side to side and front to back. If one corner is high, you can shim it up with a flat stone or a shim wedge. If one corner is low, you can dig out a little soil underneath. Make small adjustments — you do not need it perfectly level, just close enough that water does not pool.

Add soil and let it settle

Fill the bed with a mix of topsoil, compost, and peat moss or coconut coir. A common ratio is one-third of each, but you can adjust based on what you are growing and what is available locally. Do not use soil from your yard alone — it compacts and drains poorly. Bagged soil is consistent and ready to use.

For a 4-by-8-foot bed that is 10 inches deep, you will need about 26 cubic feet of soil, or roughly 1 cubic yard. Most garden centers sell soil by the bag (typically 2 cubic feet per bag) or by the cubic yard for bulk delivery. Calculate your volume and buy a little extra — soil settles as it absorbs water.

Water the bed thoroughly after you fill it. The soil will compact and settle over the first week. You may need to add more soil before you plant. This settling is normal and does not mean anything is wrong.

Protect the wood and maintain the bed

Cedar does not need sealing or staining to resist rot — that is why you chose it. Sealing it can actually trap moisture and speed decay. Leave the wood bare and let it weather to a silver-gray color. This is normal and does not affect the wood's durability.

Every few years, check the corners and the bottom edges for soft spots. If you find rot, you can replace just that board instead of the whole bed. Loosen the screws, slide out the damaged board, and screw in a new one. This is one reason screws are better than nails — you can remove and replace boards easily.

If the bed is in a very wet climate or sits on wet ground year-round, the bottom boards may rot faster than the sides. You can extend the life by raising the bed on concrete blocks or gravel so air can flow underneath. This also improves drainage.

Frequently Asked Questions

Can I use pressure-treated wood instead of cedar?

Pressure-treated wood costs less and lasts longer than untreated pine, but modern pressure-treated lumber contains copper compounds that can leach into soil over time. Cedar is safer for vegetables and herbs, and the higher upfront cost is worth it over the life of the bed. If budget is the main concern, pressure-treated wood is a reasonable choice — just avoid the oldest pressure-treated wood (pre-2004), which contained arsenic.

Do I need to line the bottom with plastic?

No. Plastic traps water and prevents soil from draining and breathing. If you have gophers or moles, use hardware cloth instead. If you do not have burrowing pests, skip the lining entirely. The soil will rest directly on the ground, and water will drain naturally.

How deep should the bed be?

Most vegetables do well in 8 to 12 inches of soil. Shallow-rooted crops like lettuce and spinach need only 6 inches. Deep-rooted crops like carrots and tomatoes prefer 12 inches or more. A 2-by-10 board gives you about 9 inches of usable depth, which works for most gardens. If you want deeper soil, stack two boards or buy 2-by-12 boards.

Can I build a raised bed on top of grass?

Yes, but the grass will eventually rot and create air pockets under the bed. It is better to remove the grass first or lay cardboard over it before you assemble the frame. Cardboard breaks down over a season and adds organic matter to the soil. Do not use glossy cardboard or cardboard with tape — use plain brown cardboard from boxes.

How long does a cedar bed actually last?

Cedar heartwood typically lasts 10 to 15 years before the bottom boards begin to rot. The sides usually outlast the bottom because they dry out faster. When rot starts, you can replace individual boards instead of rebuilding the whole bed. With good drainage and air flow underneath, some cedar beds last 20 years or more.