Most raised beds sit directly on soil with no bottom barrier, and that works fine for most gardens

Raised garden beds do not require a bottom. The vast majority are built as four-sided wooden or composite frames that sit open to the ground below. Soil, roots, and water move freely between your bed and the earth underneath, which is actually beneficial for drainage and for deep-rooted plants.

Whether you add a bottom depends on what you are trying to prevent or achieve. A bottom barrier stops burrowing pests and keeps soil separated from contaminated ground. It also slows drainage, which matters if your site is soggy. But it adds cost, weight, and maintenance work, and it can trap water or create root problems if not installed correctly.

The choice comes down to your specific situation: what is in the soil below, what pests you have, and how wet your yard gets.

Key Takeaways

  • Open-bottom beds are standard and work well in most home gardens because they allow roots to reach deeper soil and water to drain naturally.
  • Add a bottom barrier if burrowing rodents or rabbits are a problem, or if the soil below is contaminated with lead or other toxins.
  • Hardware cloth (a metal mesh) is the most common barrier material and stops rodents while still allowing water and root penetration.
  • Solid bottoms like plastic or landscape fabric can trap water and cause root rot, so they are rarely recommended unless you are growing in a contained space with no ground contact.
  • If you install a barrier, leave it loose enough that roots can eventually push through, or plan to replace it every few years as it degrades.

When an open bottom works best

An open-bottom bed is the right choice if your yard has healthy soil, no history of contamination, and no serious pest pressure. Roots from your vegetables and perennials can grow down into the native soil, accessing nutrients and water that the raised bed alone cannot provide. This is especially important for plants with deep root systems, like tomatoes, carrots, and asparagus.

Drainage also works better without a barrier. Water moves down through your bed soil and into the ground below, preventing the waterlogged conditions that cause root rot and fungal disease. If your yard slopes or drains well naturally, an open bottom is almost always the better choice.

Open-bottom beds are also cheaper and faster to build. You skip the cost of hardware cloth or plastic, the labor of installing it, and the future work of replacing it as it breaks down.

Why you might add a bottom barrier

A barrier makes sense if burrowing pests are destroying your crops. Voles, moles, gophers, and rabbits can tunnel up from below and eat roots or seedlings before you see damage. If you have lost plants this way in the past, or if neighbors report these pests, a barrier is worth the investment.

Contaminated soil is another reason. If your yard has lead from old paint, arsenic from treated wood, or industrial pollution, a barrier keeps that out of your growing space. You can have your soil tested through your county extension office if you are unsure. Barrier material does not fix contamination — it just separates your plants from it.

A barrier also slows water loss if your yard is very sandy or drains too fast. Holding moisture in the bed longer can help in dry climates, though you will need to monitor for standing water in wet seasons.

Hardware cloth versus solid barriers

Hardware cloth (a metal mesh with half-inch or quarter-inch openings) is the standard choice when you do want a barrier. It stops rodents and burrowing insects while still allowing water to drain and roots to eventually penetrate. Lay it flat on the ground before filling your bed, or staple it to the inside bottom of the frame. It lasts five to ten years depending on soil moisture and metal type — galvanized steel lasts longer than plain steel.

Solid barriers like plastic sheeting, landscape fabric, or rubber liners are tempting because they seem more protective, but they cause problems. Water pools on top of them instead of draining, creating soggy soil and root rot. Roots cannot grow down to access deeper nutrients. Plastic breaks down in sunlight and sheds microplastics into your soil. If you use a solid barrier, you are essentially creating a container garden, not a raised bed — you will need to water and fertilize more often because the roots cannot reach the native soil.

If you do use a solid barrier, drill drainage holes every few inches to prevent standing water. Even then, monitor the bed closely during heavy rain.

Installing a barrier the right way

If you decide to add hardware cloth, lay it out flat on the ground where your bed will sit. Overlap seams by at least six inches so rodents cannot squeeze through gaps. find it with landscape staples or by folding the edges up and stapling them to the inside of the frame.

Leave the barrier loose enough that roots can push through over time, or plan to replace it every five to seven years. If you pull it tight and staple it rigidly, roots will hit a hard barrier and stop growing down, which defeats part of the purpose of a raised bed.

Do not bury the edges of the barrier deep in the ground. Rodents will tunnel around it. Instead, fold the edges up the inside walls of your bed frame so they can see the barrier and move on to easier targets.

What happens if you skip the bottom entirely

In most cases, nothing bad happens. Your plants grow normally, roots reach deeper soil, and water drains well. Pests stay out because the bed itself is elevated and harder to access than ground-level planting.

If you do have burrowing pests, you will notice damage — seedlings disappearing, root vegetables with tunnels, or plants wilting despite adequate water. At that point, you can add a barrier to an existing bed by carefully lifting it, laying down hardware cloth, and resetting it. It is more work than installing it from the start, but it is possible.

If the soil below is contaminated and you did not know it, the risk is long-term. Heavy metals and some chemicals move slowly into plant tissue, so damage may not show for years. If you suspect contamination, test the soil before planting, especially if your house is old or near an industrial area.

Frequently Asked Questions

Can I use landscape fabric instead of hardware cloth?

Landscape fabric alone will not stop burrowing rodents — they can chew through it or tunnel around the edges. It does slow water drainage and can trap moisture, leading to root rot. If you use it, combine it with hardware cloth underneath, or use it only as a weed barrier on top of the soil inside the bed.

What if my raised bed is sitting on concrete or pavement?

You do not need a bottom barrier because there is nothing below to burrow up. You will need to water more often since water cannot drain into the ground, and you may want to add drainage holes or a slight slope to prevent pooling. Roots cannot grow down past the concrete, so the bed functions as a container.

Do I need a bottom if I am growing in a raised bed on a deck or patio?

No, but you do need drainage holes in the bottom of the frame or a layer of gravel to prevent water from sitting and rotting the wood. Since there is no soil below, the bed is already isolated from ground pests and contamination.

Will hardware cloth rust and contaminate my soil?

Galvanized hardware cloth resists rust for many years and does not leach harmful amounts of metal into soil. Plain steel will rust over time, but the rust itself is not toxic to plants. If you want maximum longevity, buy galvanized or stainless steel cloth, which costs more but lasts longer.

Can roots grow through hardware cloth?

Yes, over time. Roots are persistent and will find openings or push through the mesh as they grow. This is actually good — it means your plants can still access deeper soil nutrients. If you want to prevent root penetration entirely, you would need a solid barrier, which brings the drainage and rot problems mentioned earlier.