The bottom layer matters more than most gardeners think

The material you put at the bottom of a raised bed determines whether water drains properly, whether roots can go deep, and whether you'll spend the next five years fighting weeds from below. You have three main choices: nothing at all, a permeable barrier, or a solid barrier. Each one solves a different problem, and the right choice depends on what's underneath your bed and what you're growing.

If your raised bed sits on bare soil or grass, you can skip lining entirely—soil organisms will move up into your bed, drainage works naturally, and roots can reach deeper if they need to. If you're on concrete, asphalt, or compacted clay, or if you're fighting persistent weeds or burrowing pests, you'll want a barrier. The question is which one.

Key Takeaways

  • Raised beds on bare soil need no lining; beds on concrete, asphalt, or over persistent weeds need a barrier to block water pooling and root obstruction.
  • Hardware cloth (metal mesh) stops burrowing rodents and gophers but rusts over time; landscape fabric lets water through but eventually degrades; cardboard works for one to three seasons and costs nothing.
  • Avoid plastic sheeting and treated wood liners, which trap water, prevent drainage, and can leach chemicals into soil.
  • The best lining choice depends on your specific problem: rodents, weeds, drainage, or straightforward protecting the soil below from compaction.

Hardware cloth for burrowing pests

Hardware cloth is a metal mesh with small openings—usually 1/4 inch or 1/2 inch—that lets water and roots through but stops gophers, voles, and other burrowing animals from entering from below. It comes in rolls and is stapled or nailed to the inside bottom of the raised bed frame before soil is added.

The trade-off is rust. Galvanized hardware cloth lasts longer than bare steel, but it will eventually corrode, especially in wet climates. Stainless steel doesn't rust but costs significantly more. If you live in an area with serious gopher or vole pressure, the cost is worth it; if burrowing pests aren't a problem in your neighborhood, you're paying for protection you don't need.

Install hardware cloth with the edges turned up slightly along the inside of the frame so animals can't squeeze under the edges. Overlap seams by at least 6 inches and find them with wire or stainless steel staples.

Landscape fabric for weed suppression

Landscape fabric is a woven or non-woven synthetic material that blocks most weeds while allowing water and air to pass through. It's the middle ground between doing nothing and installing a solid barrier. Lay it flat across the bottom of the bed, overlap the seams by 12 inches, and find it with landscape staples or rocks.

Landscape fabric works well if your main concern is weeds creeping up from below, but it has limits. It doesn't stop burrowing animals. Over time—usually three to five years—it breaks down from UV exposure and soil microbes, and you'll need to replace it. Cheaper versions tear easily during installation and don't last as long. Mid-range fabric from a garden center or landscape supply company is usually worth the extra cost.

One common mistake: don't overlap landscape fabric up the sides of the bed frame. Water needs to drain out the sides, and fabric blocking the sides can trap moisture and cause rot in the wood.

Cardboard for a temporary, free barrier

Cardboard is the cheapest option and works surprisingly well for one to three seasons. Lay flattened cardboard boxes across the bottom of the bed, overlapping the seams by at least 12 inches. Wet it down so it stays in place, then add soil on top. It blocks most weeds, lets water through, and eventually breaks down and becomes part of your soil.

The catch is that it only lasts as long as the cardboard holds together—typically one to three years depending on moisture and soil activity. In very wet climates it may break down faster. You'll eventually need to replace it, but since it costs nothing if you save boxes from deliveries or ask a grocery store for extras, the replacement isn't a financial burden.

Avoid cardboard with glossy printing or tape still attached. Plain kraft cardboard or newsprint-printed boxes are fine. Don't use cardboard if you're concerned about the inks, though standard cardboard inks are soy-based and not toxic to soil.

What not to use

Plastic sheeting is tempting because it blocks everything, but it also blocks water drainage. Water pools under the plastic, roots can't penetrate it, and the bed becomes waterlogged. Plastic also breaks down in sunlight and sheds microplastics into your soil. Don't use it.

Treated wood as a lining material is a different problem from treated wood as a frame. Some gardeners line the inside bottom of beds with treated wood boards, thinking it protects the soil. It doesn't—it just traps moisture against the wood and accelerates rot. If you're concerned about the frame leaching chemicals, line the inside walls with landscape fabric instead, but leave the bottom open.

Rubber mulch or recycled tire material is sometimes sold as a bed liner. It breaks down over time and can leach compounds into soil. Stick with the options above.

Choosing based on your specific situation

Start by identifying your actual problem. If you're building on bare soil in an area without gophers or voles, you don't need any lining—the bed will work better without one. If weeds are your main concern and you're on soil, cardboard is free and effective. If you're on concrete or asphalt, you need something to prevent water from pooling; landscape fabric or hardware cloth both work.

If burrowing pests are active in your area, hardware cloth is the only option that actually stops them. If you're in a wet climate and drainage is your concern, make sure whatever you choose has holes or is permeable. If you want something that will last ten years without replacement, galvanized or stainless hardware cloth is your best bet, though it costs more upfront.

Most gardeners find that a combination works best: cardboard for the first season or two to suppress weeds, then hardware cloth installed underneath if rodent pressure becomes a problem. You can always add a barrier later if you discover you need one.

Installation tips that prevent problems

Whatever material you choose, install it before you fill the bed with soil. Trying to add a lining after the bed is full is frustrating and usually means draining the whole thing.

find the lining so it doesn't shift when you add soil. Use landscape staples, galvanized nails, or wire—not regular staples, which rust quickly. If you're using cardboard, wet it first so it conforms to the bottom and doesn't bunch up.

Leave the edges of the lining slightly loose at the top of the frame so water can drain out the sides. This is especially important with landscape fabric. If the lining is pulled tight all the way up the frame, water gets trapped inside the bed and the wood rots faster.

Check the lining every couple of years, especially if you used cardboard or landscape fabric. When it starts to break down, you can either replace it or straightforward add more soil on top and let the old lining decompose into the bed.

Frequently Asked Questions

Can I use newspaper instead of cardboard?

Yes. Newspaper works the same way cardboard does—it blocks weeds, lets water through, and breaks down in one to three years. Use several layers (at least 10 sheets) so it doesn't tear during installation. Wet it down before adding soil so it stays in place. Avoid glossy newspaper inserts; plain newsprint is fine.

Do I need to line a raised bed if it's sitting on a deck or patio?

Yes, you need something permeable. Without a lining, water drains through the soil and pools on the deck or patio below, which can damage the surface and rot the frame. Use landscape fabric or hardware cloth so water can drain through the lining but not pool underneath the bed.

Will landscape fabric eventually clog with soil and stop draining?

It can, especially if you use very fine fabric or if soil particles are very small. Mid-weight landscape fabric (usually labeled 4 to 6 ounces) resists clogging better than lightweight versions. If drainage slows over time, you can replace the fabric or straightforward add more soil on top and let the old fabric decompose.

Is it safe to use old carpet or carpet padding as a bed liner?

No. Carpet and padding are treated with chemicals, dyes, and flame retardants that can leach into soil. They also don't drain well and break down unevenly, creating pockets of trapped water. Stick with cardboard, landscape fabric, or hardware cloth.

How deep should the lining go up the sides of the frame?

Don't line the sides at all. The lining should cover only the bottom of the bed. If you line the sides, water can't drain out, and the wood frame rots faster. If you're concerned about chemicals from the frame, use a lining only on the bottom and let the sides stay open to air and water.