Lining a raised bed stops weeds from growing up through the bottom and keeps soil from washing into the ground below

A raised bed liner is a barrier you place on the ground before you fill the bed with soil. It blocks weeds from pushing up from underneath, prevents soil from mixing with contaminated earth, and keeps your planting area separate from grass or compacted ground. You do not need to line every raised bed — it depends on what is underneath — but lining takes about 30 minutes and saves months of weeding later.

The most common mistake is using plastic that will not break down. Plastic traps moisture, rots wood faster, and eventually fragments into microplastics in your soil. Cardboard, landscape fabric, and hardware cloth are the practical choices, and you can use them alone or in layers depending on what problem you are solving.

Key Takeaways

  • Cardboard is the cheapest liner and breaks down in one to two years, making it ideal for beds over grass or weeds.
  • Landscape fabric lasts five to ten years and works best over bare soil or as a second layer under cardboard.
  • Hardware cloth (metal mesh) stops burrowing rodents and goes underneath other liners if that is your main concern.
  • Overlap all seams by at least 6 inches so weeds cannot push through the gaps.
  • Wet cardboard before laying it so it stays in place and makes better contact with the ground.

Cardboard: the fastest and cheapest option

Cardboard is the best choice if your raised bed sits on grass, weeds, or soil you want to smother. It is cheap (often free from grocery stores or appliance shops), straightforward to cut, and breaks down naturally in 12 to 24 months, adding organic matter to the soil below. By the time it disintegrates, the weeds underneath will have died and your soil will have settled.

Use corrugated cardboard at least 1/4 inch thick — single-wall is fine. Avoid cardboard with plastic tape, glossy printing, or wax coating; plain kraft cardboard works best. Remove any plastic tape before laying it down. Wet the cardboard thoroughly with a hose so it stays flat and adheres to the ground, then lay pieces so they overlap by at least 6 inches. Overlap is critical: weeds will find any gap and push through. Overlap the edges where cardboard meets the raised bed frame too.

After the cardboard is down, you can fill the bed when ready. As you water the bed over the coming weeks, the cardboard will soften and compress. By the second season, it will have mostly broken down, and you can add a second layer if you want longer protection.

Landscape fabric: the middle ground for durability

Landscape fabric (also called weed cloth) is a woven or non-woven synthetic material that lasts five to ten years. It lets water and air through while blocking light, so weeds cannot grow. It costs more than cardboard but less than replacing cardboard every two years, and it does not break down into your soil.

Buy landscape fabric rated for gardens, not the thin stuff sold for mulch. Lay it flat on the ground and overlap seams by at least 6 inches. You can staple it to the inside of the raised bed frame to hold it in place, or weight it down with soil as you fill the bed. If your ground is very uneven, smooth it first with a rake or shovel — fabric that does not touch the soil leaves gaps where weeds can grow around the edges.

Landscape fabric works especially well as a second layer under cardboard. The cardboard breaks down and feeds the soil, while the fabric underneath continues blocking weeds for years after the cardboard is gone. This combination is popular in vegetable gardens where you want both short-term decomposition and long-term weed control.

Hardware cloth: protection against burrowing rodents

If gophers, moles, or voles are a problem in your area, hardware cloth (galvanized steel mesh with 1/4-inch or 1/2-inch holes) goes on the ground under your other liners. It stops rodents from tunneling up into your bed while still allowing water and roots to pass through. Hardware cloth alone does not stop weeds, so use it with cardboard or landscape fabric on top.

Lay hardware cloth flat and overlap seams by at least 2 inches. Bend the edges up slightly where they meet the raised bed frame so rodents cannot burrow around the sides. This is the most labor-intensive liner because the mesh is stiff and can pinch your hands, but it is the only liner that stops burrowing pests. If rodents are not an issue, skip this step — it adds cost and complexity without benefit.

Preparing the ground before you line

Spend a few minutes preparing the ground so your liner makes full contact and does not shift. Remove large rocks, sticks, and debris. If the ground is very lumpy, rake it smooth. You do not need to remove grass or weeds — the liner will smother them — but if you have a thick mat of dead grass or thatch, scrape it away so the liner sits on bare soil.

If the ground is very wet or muddy, wait a day or two for it to dry slightly. Wet ground makes cardboard soggy and hard to handle, and it prevents landscape fabric from settling properly. If the ground is very hard and compacted, water it the day before so it is easier to work with.

Laying the liner and filling the bed

Start at one corner and unroll or lay out your liner material. Work in one direction — usually along the length of the bed — so you can see where seams overlap. For cardboard, wet each piece as you lay it. For landscape fabric, smooth it as you go so it lies flat without wrinkles.

Overlap seams by at least 6 inches. This is the most important step: a 2-inch overlap will fail within weeks as weeds find the gap. Overlap the edges where the liner meets the raised bed frame by at least 3 inches so weeds cannot grow around the perimeter. If you are using hardware cloth, lay it first, then overlap landscape fabric or cardboard on top of it.

Once the liner is down, you can fill the bed with soil when ready. As you pour soil, it will weight down the liner and hold it in place. You do not need to staple or nail cardboard, but you can staple landscape fabric to the inside of the frame if you want extra security. Avoid stapling cardboard — the staples will rust and the cardboard will break down anyway.

Common mistakes and how to avoid them

The biggest mistake is using plastic sheeting or plastic bags. Plastic does not break down, traps water against the wood frame (rotting it faster), and eventually fragments into microplastics. Avoid it entirely. The second mistake is overlapping seams by less than 6 inches. Weeds are persistent and will find any gap. Measure your overlaps and do not skimp.

A third mistake is laying cardboard on wet ground without wetting it first. Dry cardboard will not stay in place and will shift as you fill the bed. Wet it thoroughly before laying it down. Finally, do not assume you need a liner if your raised bed sits on bare, weed-free soil. If the ground underneath is clean and you do not have a rodent problem, you can skip lining entirely and save the time and cost.

Frequently Asked Questions

Can I use newspaper instead of cardboard?

Newspaper works in a pinch, but it is thinner than cardboard and breaks down faster — usually in 6 to 12 months instead of 12 to 24. Use at least 10 sheets thick, overlap by 6 inches, and wet it thoroughly before laying it down. Cardboard is more durable and easier to handle, so it is the better choice if you can get it.

Do I need to remove the liner after it breaks down?

No. Cardboard and landscape fabric break down into the soil and add organic matter. You do not need to remove them. If you are using hardware cloth, it will not break down, but it will sink into the soil and you can leave it there — it will not harm plants or roots.

What if my raised bed is on concrete or a patio?

You still need a liner to prevent soil from washing out the bottom and to keep roots from growing into cracks. Cardboard or landscape fabric works the same way. The concrete underneath will not rot, so you can use plastic if you want, but cardboard and fabric are better for soil health.

Can I line a raised bed after I have already filled it with soil?

It is much harder but possible. You would need to remove the soil, lay the liner, and refill. If weeds are already growing through, pull them out first, then lay cardboard or fabric on top of the soil and weight it down with mulch or compost. This is less effective than lining before filling, but it will slow weeds for a season or two.

How do I know if my ground has contaminated soil?

If your raised bed is in an old industrial area, near a busy road, or on land that was previously used for something other than gardening, the soil underneath may contain heavy metals or other contaminants. A liner prevents your soil from mixing with the ground below, which is a good precaution. If you are concerned, a soil test from your local extension office can tell you whether contamination is present.