What You Need to Build a Legged Raised Bed

A raised bed with legs is a wooden or composite box set on a frame, typically 12 to 24 inches off the ground. You build it by constructing a rectangular frame from boards, then attaching four vertical posts at the corners to create the legs. The whole structure takes a weekend and requires basic tools: a drill, a saw, a level, and a tape measure. Most people spend $80 to $300 on materials, depending on the size and wood type.

The main advantage over a ground-level bed is that you avoid bending as far to plant and weed, and you can place it on concrete, gravel, or poor soil without digging. The legs also keep the bed away from ground moisture, which extends the life of the wood. The trade-off is that a legged bed dries out faster than one sitting on soil, so you will water more often in summer.

Key Takeaways

  • A legged raised bed is built from four boards forming a rectangle, with four posts screwed to the corners to create the frame that holds it up.
  • Cedar, composite, or untreated pine are the most common materials; avoid pressure-treated wood if you plan to grow vegetables, because the chemicals can leach into soil.
  • The bed should sit on level ground, and the legs should be long enough to clear grass or weeds underneath so they do not rot from contact with damp soil.
  • Assembly takes two to four hours and requires a drill, a saw, a level, and a tape measure; no special skills are needed if you follow the measurements carefully.

Choosing Wood and Sizing Your Bed

Cedar is the most popular choice because it resists rot naturally and lasts 10 to 15 years. It costs more than pine but requires no treatment. Composite boards (wood fiber mixed with plastic) last 20+ years and never rot, but cost two to three times as much as cedar and are heavier to work with. Untreated pine is the cheapest option and works fine, but will rot in 5 to 7 years unless you line the interior with landscape fabric to slow moisture contact.

Standard dimensions are 4 feet by 8 feet by 12 inches deep, which gives you enough room to grow most vegetables and fits through a standard gate. If you want it higher for easier access, build it 18 to 24 inches deep instead. The legs should extend 12 to 18 inches below the bottom of the box so the bed sits well clear of ground moisture. A 4x8 bed with 18-inch legs will hold roughly 32 cubic feet of soil, which costs $30 to $60 to fill depending on your region.

Cutting and Assembling the Frame

Start by cutting your boards to length. For a 4x8 bed, you need two boards 8 feet long and two boards 4 feet long. Cut four posts from 4x4 lumber or 2x4 lumber, each one 18 inches long (or whatever height you want your legs to be). Lay the boards flat on the ground in a rectangle and check that the corners are square by measuring diagonally from corner to corner — both diagonals should be the same length.

Drill pilot holes (small holes to guide the screw) at each corner, then screw the boards together using 3-inch exterior wood screws, two screws per corner. Attach the posts to the outside of each corner by drilling pilot holes through the board into the post, then driving 3-inch screws through the board and into the post. Make sure the posts are vertical by checking with a level before you tighten the final screws. Once all four posts are attached, flip the whole frame over so the legs point down and set it on level ground.

Leveling and Positioning Your Bed

Set the bed on the spot where you want it to stay — moving it later is difficult once it is full of soil. Use a level to check that the top of the frame is even in both directions. If the ground slopes, you have two options: dig out the high side slightly and backfill the low side with soil, or shim the legs with wood shims or concrete shims until the top is level. Uneven beds cause water to pool on one side and dry out on the other, which stresses plants.

Make sure the legs are not touching grass or weeds, because contact with damp vegetation will rot the wood faster. If grass is growing under the bed, pull it out or cover the ground underneath with cardboard or landscape fabric. This also prevents weeds from growing up through the bottom of the bed later.

Lining and Filling Your Bed

Line the interior bottom with landscape fabric (the kind that lets water through but blocks weeds). Staple it to the inside of the boards so it stays in place when you add soil. This step is optional if you used cedar or composite, but it extends the life of the wood by keeping it from sitting in wet soil. If you used untreated pine, lining is strongly recommended.

Fill the bed with a mix of topsoil and compost — roughly 60 percent topsoil and 40 percent compost works well for most vegetables. Avoid filling it completely with compost alone, because it settles and compacts over time. Water the soil as you fill so it settles and you can see how much more you need. The soil will settle another inch or two over the first few weeks, so slightly overfilling is normal.

Maintenance and Extending Bed Life

Cedar and composite need no treatment, but untreated pine benefits from a coat of exterior wood stain every two to three years. Do not use paint, because it traps moisture and speeds rot. Check the posts and corners each spring for soft spots or cracks; soft wood means rot has started and that section may need replacing.

In winter, drain any standing water from the bed and remove dead plant material so it does not trap moisture against the wood. If you live in a very wet climate, consider raising the legs another few inches or adding a gravel layer underneath to improve drainage. A well-maintained cedar bed typically lasts 12 to 15 years before the boards need replacing; composite lasts much longer but is harder to repair if a section breaks.

Frequently Asked Questions

Can I use pressure-treated wood for a vegetable garden?

Older pressure-treated wood (before 2004) contained arsenic and should not be used for food gardens. Modern pressure-treated wood uses copper-based preservatives, which are safer but can still leach into soil over time. Cedar, composite, or untreated pine are better choices if you are growing vegetables.

How deep does a legged bed need to be?

Twelve inches is the minimum for shallow-rooted crops like lettuce and herbs. Most vegetables need 12 to 18 inches. Root vegetables like carrots and parsnips do better with 18 to 24 inches. Deeper beds also hold more moisture, which matters if you live in a dry climate.

Do I need to put anything on the bottom of the bed to keep pests out?

Landscape fabric stops weeds but does not stop burrowing pests like voles or moles. If you have a serious pest problem, you can line the bottom with hardware cloth (a metal mesh), but this adds cost and makes it harder to work the soil later. Most gardeners skip this step and monitor for damage instead.

Can I build a legged bed on a deck or patio?

Yes, as long as the deck or patio can support the weight. A 4x8 bed filled with soil weighs roughly 1,200 to 1,500 pounds, so check that your deck is rated for that load. Use landscape fabric on the bottom to protect the surface underneath from moisture and staining.

How often should I water a legged bed?

Legged beds dry out faster than ground-level beds because air circulates underneath. In summer heat, you may need to water every day or every other day, depending on your climate and soil mix. Check the soil 2 inches down — if it feels dry, water. Adding mulch on top helps retain moisture.