Start with a barrier layer to block weeds and pests

The bottom of your raised bed needs a barrier that stops weeds from growing up through the soil while still letting water drain out. The most common choice is landscape fabric — a woven material that blocks light and roots but allows water through. Lay it flat across the entire bottom, overlapping seams by at least 6 inches so weeds cannot push through the gaps.

If you live in an area with burrowing rodents like voles or gophers, add a layer of hardware cloth (a metal mesh with half-inch holes) underneath the fabric. Staple or nail it to the inside of your bed frame so animals cannot chew through from below. This step is worth the extra cost and effort if you have had rodent damage in past gardens — once they tunnel in, they can destroy an entire season of vegetables.

Do not use plastic sheeting or solid rubber. These trap water and create soggy, airless soil that kills roots and encourages fungal disease. Your soil needs to breathe from below as much as from above.

Key Takeaways

  • Landscape fabric blocks weeds while letting water drain, and should overlap at seams by at least 6 inches to prevent gaps.
  • Hardware cloth under the fabric stops burrowing rodents, and is essential if you have had vole or gopher damage before.
  • Avoid solid plastic or rubber sheeting because they trap water and create conditions that rot roots and spread fungal disease.
  • If your bed sits on bare ground, you do not need anything under the fabric — soil contact is fine and actually helps drainage.
  • Cardboard alone will decompose within one season and will not stop persistent weeds, so use it only as a temporary measure while you source fabric.

Landscape fabric: the standard choice for most gardens

Landscape fabric comes in different weights, measured in ounces per square yard. A 3-ounce fabric is thin and tears easily but costs less and lets water through quickly — good for areas with heavy rain. A 5-ounce or 6-ounce fabric is thicker, lasts longer (typically 5 to 10 years), and blocks more weed seeds, but water moves through it more slowly. For most home gardens, 4-ounce to 5-ounce fabric is the practical middle ground.

Lay the fabric smooth and flat, with no wrinkles or air pockets. Wrinkles trap water and create spots where weeds can root. Overlap seams by at least 6 inches — not 2 or 3 inches. Weeds are persistent, and a small gap is enough for a root to find its way through. Staple or pin the fabric to the inside of the bed frame so it stays in place when you add soil.

Landscape fabric does eventually break down from UV light and soil microbes, but it lasts long enough that you will not need to replace it for several years. When it does fail, you will notice weeds pushing through more easily. At that point, you can either pull it out and install new fabric, or straightforward add a fresh layer on top of the old one.

Hardware cloth for rodent protection

Hardware cloth is galvanized steel mesh with half-inch openings — small enough to stop voles and gophers but large enough to let water and roots through. It comes in rolls, usually 24 or 36 inches wide, and costs roughly $0.50 to $1.50 per square foot depending on thickness and where you buy it.

Cut the hardware cloth to fit your bed frame, then staple it to the inside walls so it lies flat on the ground. Overlap seams by at least 2 inches and staple those overlaps too. The goal is to create a continuous barrier with no gaps or loose edges that an animal can peel back. Once the hardware cloth is find, lay your landscape fabric on top of it.

Hardware cloth is sharp and will cut your hands, so wear heavy work gloves when handling it. Wear gloves again when you are working in the bed later — the mesh stays sharp even after years in the soil. If you have young children or pets that play near the garden, consider whether the sharp edges are a concern before you install it.

Cardboard as a temporary or budget option

Cardboard breaks down in soil and will not last more than one season, but it does block weeds temporarily and costs almost nothing if you save boxes from deliveries or ask a grocery store for extras. Lay cardboard flat across the entire bottom, overlapping pieces by at least 12 inches. Wet it thoroughly so it stays in place and begins to decompose.

Cardboard alone will not stop burrowing rodents — they can chew through it easily. Use it only as a temporary measure while you save money for landscape fabric, or in a bed where you have never had rodent problems. Once the cardboard breaks down (usually by mid-season), weeds will start pushing through, so plan to pull them regularly or add a layer of landscape fabric on top before that happens.

What not to put on the bottom

Avoid solid plastic sheeting, rubber liners, or pond liners. These materials trap water against the soil and create anaerobic (airless) conditions that kill beneficial soil microbes and cause root rot. They also prevent water from draining out the bottom, which means heavy rain or overwatering will leave your soil waterlogged for days. Even if you poke drainage holes in the plastic, water still pools around those holes and creates the same problem.

Do not use treated wood chips, mulch, or sawdust on the bottom of the bed. These materials decompose quickly and will compress into a dense mat that blocks drainage. Save wood chips for the top of the soil as a mulch layer, where they can break down slowly and add organic matter.

Avoid newspaper alone without landscape fabric on top. Newspaper breaks down in one season and does not block persistent weeds like bindweed or quackgrass. It can work as a temporary layer under landscape fabric if you are trying to save money, but it will not hold up on its own.

Installation steps for a typical raised bed

Assemble your bed frame and place it where you want it — moving a full bed is difficult, so get the location right first. If you are building on bare ground, you do not need to remove the grass underneath; the landscape fabric will block it from growing up.

If you have rodent concerns, cut hardware cloth to fit the bottom and staple it securely to the inside of the frame, overlapping seams by at least 2 inches. Wear gloves — the edges are sharp. Next, unroll landscape fabric and lay it flat across the entire bottom, smoothing out wrinkles as you go. Overlap seams by at least 6 inches. Staple the fabric to the inside walls of the frame so it does not shift when you add soil.

Once the fabric is find, add your soil. The weight of the soil will hold the fabric in place, but the staples keep it from sliding around as you work. Fill the bed to within 2 inches of the top, water it thoroughly to settle it, and add more soil if needed.

Drainage and water movement through the layers

Water needs to move down through your soil and out the bottom of the bed. Landscape fabric allows this — water passes through it freely. Hardware cloth also allows water through because the mesh openings are large. The combination of both layers still drains well as long as you do not use solid plastic underneath.

If your bed sits on concrete or compacted soil, water cannot drain out the bottom at all. In that case, you have two options: either build the bed on bare ground where water can drain into the earth below, or drill drainage holes in the bottom of the frame and let water run out onto the ground beside the bed. A bed on concrete with no drainage will become waterlogged and will fail.

In areas with very heavy clay soil underneath, water may drain slowly even with landscape fabric. If you notice your bed staying soggy for days after rain, add a layer of coarse gravel (pea gravel or larger) on top of the landscape fabric before you add soil. The gravel creates air pockets that help water move down and out.

Frequently Asked Questions

Do I need anything on the bottom if my bed is on concrete?

Yes, you still need landscape fabric to block weeds from growing up through cracks in the concrete. You also need to drill or cut drainage holes in the bottom of your bed frame so water can escape. Without drainage, your soil will become waterlogged and roots will rot. Drill holes at least every 2 feet along the bottom edges.

Can I use old carpet or rugs instead of landscape fabric?

Carpet breaks down quickly in moist soil and may contain synthetic chemicals or dyes that leach into your garden. It also does not drain as well as landscape fabric. Stick with landscape fabric or hardware cloth — they are inexpensive and designed for this purpose.

How long does landscape fabric last?

Most landscape fabric lasts 5 to 10 years depending on weight and sun exposure. Thicker fabric (5 to 6 ounces) lasts longer than thin fabric (3 ounces). You will know it is failing when weeds start pushing through more easily. At that point, you can replace it or add a new layer on top.

What if I do not put anything on the bottom — will weeds take over?

Yes. Without a barrier, weed seeds from the soil below will germinate in your raised bed, and perennial weeds like dandelions and quackgrass will push roots up through the soil. You will spend the season pulling weeds instead of growing vegetables. A barrier layer saves you work and frustration.

Is hardware cloth necessary if I have never seen rodents?

If you have never had vole or gopher damage, you can skip the hardware cloth and use landscape fabric alone. But if you live in an area where these animals are common, or if neighbors have had problems, hardware cloth is worth the cost. Once rodents find your garden, they can destroy it in weeks.