The purpose of what goes underneath your raised bed
What you put under a raised garden bed serves two main jobs: stopping weeds from growing up through the soil, and blocking burrowing pests like moles and voles from tunneling in from below. You do not need anything underneath if your raised bed sits on solid concrete or asphalt, but on bare ground or grass, a barrier makes a real difference in how much weeding you will do and how many rodents will eat your vegetables.
The material you choose depends on your budget, how long you want it to last, and whether you care about it breaking down over time. Some gardeners use cardboard because it is free and biodegradable. Others use landscape fabric or hardware cloth because they last longer and work more reliably. Many use a combination of two layers for better protection.
Key Takeaways
- Cardboard is the cheapest option and works well for one to two seasons, but breaks down faster in wet soil and does not stop determined burrowing animals.
- Landscape fabric (also called weed cloth) lasts three to five years, stops most weeds, but allows water through and does not block rodents without a second layer underneath.
- Hardware cloth with half-inch or quarter-inch openings stops burrowing pests completely but costs more and can rust over time unless you buy galvanized or stainless steel.
- Many gardeners layer cardboard or landscape fabric on top of hardware cloth to get both weed and pest protection in one setup.
- Whatever you choose, overlap seams by at least six inches and extend the barrier slightly up the sides of the bed to stop pests from burrowing around the edges.
Cardboard: the free and temporary option
Cardboard is the most common choice because it costs nothing if you save boxes from deliveries or ask a grocery store for extras. Lay it flat on the ground, overlapping pieces by at least six inches so weeds cannot push through the seams. Wet it down so it stays in place while you fill the bed with soil.
Cardboard works well for blocking weeds for the first year or two, but it breaks down faster in wet climates or if your soil stays constantly moist. In dry conditions it can last longer. It does almost nothing to stop burrowing rodents—they will chew through it or tunnel underneath the edges. Remove any plastic tape or stickers before laying it down, since those do not break down.
The advantage is that as cardboard decomposes, it adds organic matter to the soil below. The disadvantage is that you will need to replace it every couple of years, and you have to pull out the rotted pieces to do so.
Landscape fabric: the middle-ground choice
Landscape fabric (also called weed cloth or geotextile) is a synthetic material that lets water and air through but blocks most weeds. It lasts three to five years depending on sun exposure and quality. Lay it flat, overlap seams by at least six inches, and pin it down with landscape staples or rocks so it does not shift when you fill the bed.
Landscape fabric stops weeds reliably, but it does not block burrowing pests. Moles, voles, and gophers will tunnel right underneath it. If rodents are a problem in your area, you need hardware cloth underneath the fabric, or you need to accept that you will have some pest pressure.
One drawback: over time, soil and organic matter settle on top of the fabric, and weeds can root into that layer. You will still do less weeding than with no barrier, but not zero. Some gardeners replace landscape fabric every three to four years rather than waiting for it to fail completely.
Hardware cloth: the pest-proof barrier
Hardware cloth is a metal mesh with small square openings, usually half-inch or quarter-inch. Quarter-inch stops smaller rodents like voles; half-inch stops larger ones like moles and gophers but lets some smaller pests through. Lay it flat on the ground, overlapping seams by at least six inches, and extend it up the sides of your raised bed by two to three inches so animals cannot burrow around the edges.
Hardware cloth is the most effective barrier against burrowing pests, but it costs more than cardboard or landscape fabric—typically $0.50 to $1.50 per square foot depending on mesh size and material. Standard galvanized hardware cloth will rust over five to ten years. Stainless steel lasts much longer but costs significantly more. Vinyl-coated hardware cloth splits the difference on price and lifespan.
Hardware cloth alone does not stop weeds, so most gardeners layer landscape fabric or cardboard on top of it. This combination gives you both weed and pest protection. The hardware cloth sits directly on the ground, and the fabric sits on top of the cloth.
Combination setups that work best
Many experienced gardeners use two layers because each material does one job well. The most common setup is hardware cloth on the bottom (for pests) and landscape fabric on top (for weeds). Overlap all seams by at least six inches, and make sure the hardware cloth extends up the sides of the bed.
Another option is cardboard on the bottom and landscape fabric on top. This is cheaper than hardware cloth and works fine if burrowing pests are not a major problem in your area. The cardboard breaks down over time, but by then the landscape fabric is doing most of the weed-blocking work anyway.
If you are on a tight budget and pests are not an issue, cardboard alone is a reasonable starting point. You can always add hardware cloth underneath later if you find yourself fighting rodents.
How to install the barrier correctly
Start by clearing the ground of large rocks and debris so the barrier sits flat. Lay your first layer (hardware cloth, cardboard, or landscape fabric) directly on the soil. Overlap seams by at least six inches—this is the most common mistake people make, and it is why weeds or pests find their way in.
If you are using hardware cloth, fold the edges up the sides of your raised bed and find them with staples or wire. This stops animals from burrowing around the perimeter. If you are using cardboard or landscape fabric, you can tuck the edges under the bottom board of the bed or weight them down with rocks.
Fill the bed with soil on top of the barrier. The soil will hold the barrier in place and keep it from shifting. If you are using a combination of materials, install the bottom layer first, then the top layer, overlapping both sets of seams.
When you might not need a barrier
If your raised bed sits on solid concrete, asphalt, or a deck, you do not need anything underneath—weeds cannot grow through solid surfaces, and burrowing pests cannot tunnel through them. If your raised bed is very shallow (less than six inches deep), a barrier is less critical because most weeds will not reach far enough to cause problems.
If you live in an area with no burrowing rodents and you do not mind doing some weeding, you can skip the barrier entirely. Many gardeners find that the time and cost of installing a barrier is worth it, but it is not absolutely necessary for a raised bed to work.
Frequently Asked Questions
Can I use plastic sheeting instead of landscape fabric?
Plastic sheeting blocks weeds and pests, but it also blocks water and air from reaching the soil below. Over time, this can create a waterlogged layer that smells bad and kills beneficial soil organisms. Landscape fabric or hardware cloth are better choices because they let water through while still blocking weeds and pests.
How deep should the hardware cloth go into the ground?
Hardware cloth does not need to go into the ground—it sits flat on top of the soil. What matters is that it extends up the sides of your raised bed by two to three inches and overlaps all seams by at least six inches. This stops animals from burrowing around the edges or through the gaps.
Do I need to replace the barrier every year?
Cardboard breaks down in one to two years and should be replaced. Landscape fabric lasts three to five years. Hardware cloth lasts five to ten years if galvanized, longer if stainless steel. You do not need to replace it every year, but you should inspect it occasionally and replace it when it starts to fail.
What if I already built my raised bed without a barrier?
You can still add one. Carefully remove the soil from the bed, lay down your barrier material, and refill. It is more work than installing it before filling, but it is doable. Alternatively, you can accept some weeding and pest pressure and add a barrier the next time you rebuild the bed.
Will a barrier stop all weeds?
A barrier stops most weeds from growing up from the ground below, but weeds can still blow in as seeds and root into the soil on top of the barrier. You will do significantly less weeding than without a barrier, but you will not eliminate weeding entirely.