Updated:
Start with the ground under the bed. On usable garden soil, an open bottom can preserve access to the soil below. Over lawn, plain cardboard can be a temporary smothering layer. Where pocket gophers are the problem, secured wire mesh can help exclude them from below. On concrete, plan soil containment and a water outlet together. A taller wall does not make an unsuitable site drain well.
Choose the barrier for a specific problem: weeds, gophers, or soil containment. Those jobs need different materials and installation checks.
This is source-based planning advice; we have not field-tested these products. Amazon links are affiliate links, and qualifying purchases may earn us a commission. Check the selected configuration, installation instructions, price, and availability before buying.
Quick Answer
| Situation | Best bottom choice | Why |
|---|---|---|
| Bed over usable, well-drained garden soil | Usually no permanent barrier | Keeps access to underlying soil; does not repair poor drainage |
| Bed over lawn or annual weeds | Plain cardboard as a temporary smothering layer | Needs time to suppress vegetation; perennial weeds need separate control |
| Pocket gophers are confirmed | Wire mesh fitted to the bed footprint and sides | Helps exclude entry from below; gaps and aboveground access still matter |
| Bed over concrete or patio | Suitable planter or supported containment design with drainage | A permeable liner alone does not create an outlet or carry the load |
| Very deep bed | Preserve usable rooting depth before considering lower filler | Wall height alone does not determine which crops or layers will fit |
| Poor drainage site | Fix location or soil mix first | Rocks or plastic do not solve a bad site |
What Most Raised Beds Need at the Bottom
An open bottom and good drainage are different decisions. University of Maryland Extension's soil-fill guide separates existing garden soil, compacted ground, turf, and hard surfaces. Assess the underlying soil before choosing a barrier. Its minimum-till approach uses a fork or spade to loosen compacted soil without turning it over; adding a bed frame alone is not the treatment.
Cardboard is a temporary smothering layer, not a drainage layer. Remove tape and labels, use plain uncoated material, and allow time for vegetation to die before planting.
For pocket gophers, UC IPM describes mesh beneath raised vegetable beds and screening the sides and bottom of small planting areas. The barrier needs continuous coverage and secure edges. This evidence concerns gophers; it does not establish that one bottom mesh excludes voles, mice, chipmunks, or animals reaching plants from above.
Landscape fabric is more situational. It can help hold soil in place on a hard surface if water can pass through, but it is usually not needed between soil and an open-bottom bed. Plastic sheeting is the one to avoid in most raised-bed bottoms because it blocks drainage.
Products Where Bottom Choice Matters
Vego Garden 17" Tall 9-in-1 Modular Metal Raised Garden Bed Kit
Best for: Most open-bottom backyard vegetable beds where no permanent bottom barrier is needed.
Why this pick: Compare a specific modular kit; confirm its selected configuration.
- Height
- 17"
- Size
- up to 8 ft x 2 ft configuration; 9 possible layouts
- Type
- modular metal raised bed
Key tradeoff: Check the selected layout, included hardware and accessory mounting requirements.
Not best for: Shoppers who have not measured their space, fill volume, and walking clearance.
Key features
- 17-inch open-bottom profile
- 9-in-1 modular layouts
- Premium coated metal panels
- Measure crop rooting space and underlying soil separately
Pros
- An option to compare for an open-bottom layout
- Keeps contact with suitable underlying soil
- Estimate fill cost for the selected configuration
Cons
- Needs site prep if placed over grass
- Hardware cloth is extra if burrowing pests are present
- More assembly than a simple rectangle
Sunnydaze 5 x 5 x 1 ft L-Shaped Galvanized Raised Garden Bed
Best for: A corner footprint to compare after checking crop depth and preparing the ground.
Why this pick: Compare exact footprint, usable planting depth, parts and current total cost with rectangular alternatives.
- Height
- 12"
- Size
- 5 ft x 5 ft x 1 ft L-shaped layout
- Type
- l-shaped galvanized metal raised bed
Key tradeoff: Verify actual planting depth, assembly instructions and placement requirements
Not best for: Shoppers who have not measured their space, fill volume, and walking clearance.
Key features
- 12-inch L-shaped bed
- Open-bottom galvanized design
- Corner-friendly footprint
- Good for shallow-root crops and mixed plantings
Pros
- Useful shape for awkward corners
- Lower fill volume than tall beds
- Good fit for herbs, greens, and flowers
Cons
- Not deep enough for every vegetable plan
- No room for bulky lower layers
- Less efficient for row-style production
SnugNiture 36" Tall 8 x 4 ft Galvanized Metal Raised Bed
Best for: Deep low-bend gardens where the bottom layer and fill strategy decide the real project cost.
Why this pick: Compare recorded tall-bed dimensions; height alone is not an accessibility test.
- Height
- 36"
- Size
- 8 ft x 4 ft x 3 ft
- Type
- extra tall galvanized metal raised bed
Key tradeoff: Measure reach and path access
Not best for: Shoppers who have not measured their space, fill volume, and walking clearance.
Key features
- 36-inch tall profile
- 8 ft x 4 ft footprint
- Open-bottom deep bed
- Large vegetable capacity
Pros
- Strong comfort-height option
- Can use clean lower bulk layers to reduce fill cost
- Large enough for serious vegetable layouts
Cons
- Huge soil volume requirement
- Bottom planning matters more than on shallow beds
- Too large for many small yards
Vego Garden Elevated Raised Garden Bed V Series 2 ft x 4 ft
Best for: Patios, renters, and hard surfaces where an open-bottom bed is not the right category.
Why this pick: Supported planter requirements versus ground-bed placement
- Height
- about 32" total height; 12" planting depth
- Size
- 2 ft x 4 ft
- Type
- elevated bed with legs and storage rack
Key tradeoff: Verify manufacturer filled-load and installation requirements
Not best for: Deep-root vegetable growers who need more soil volume than a planter box can hold.
Key features
- Elevated working height
- 2 ft x 4 ft planter box
- Storage rack
- Container-style growing
Pros
- Better for patios than open-bottom beds
- No need to build directly over soil
- Comfortable for herbs, greens, and compact vegetables
Cons
- Less root volume than open-bottom beds
- Needs container-style drainage and watering
- Not ideal for large deep-root crop plans
Bottom-layer decision
Choose the bottom layer by what problem you are solving
A bottom layer should solve weeds, pests, hard surfaces, or fill cost without blocking drainage.
No permanent barrier
Preserves access to usable underlying soil.
Watch out: Check compaction, drainage, and soil suitability first.
Plain cardboard
It suppresses grass while breaking down over time.
Watch out: Avoid glossy or plastic-coated material.
Continuous wire-mesh barrier
Helps exclude gophers entering from below.
Watch out: Secure seams and sides; identify other pests separately.
Suitable contained design with an outlet
Soil retention, drainage, and support must work together.
Watch out: Do not seal an open-bottom frame with an undrained sheet.
Scenario 1: Bed Over Existing Garden Soil
If the soil underneath is safe, not badly compacted, and not full of aggressive perennial weeds, the best bottom layer is usually no bottom layer. Loosen the surface, remove large weeds, place the bed, and fill with a good root-zone mix.
Check what happens at the site after rain before filling. Standing water or severely compacted subsoil needs attention even when the frame has no bottom. A 17-inch wall is a dimension, not proof of suitable rooting depth or drainage. Match the crop plan to usable soil above and below the frame; see Best Soil for Raised Garden Beds for the growing-mix decision.
Scenario 2: Bed Over Grass or Weeds
Plain cardboard is an option for smothering turf, not instant weed removal. Maryland Extension describes covering it with compost in fall or early spring and allowing roughly six to eight weeks for the vegetation to die and decompose. Plan that lead time before planting. Results depend on the vegetation and conditions at your site.
Do not use glossy cardboard, plastic-coated boxes, tape, or labels. Do not assume cardboard is permanent weed control. Deep-rooted perennial weeds can still be a problem, and aggressive weeds should be removed before the bed goes in.
Scenario 3: Burrowing Pests
Identify the animal before buying mesh. UC IPM's pocket-gopher guidance supports a barrier underneath the growing area, but also notes that gophers can feed aboveground. A bottom-only barrier does not address that route. Inspect the whole footprint, corners, side connection, and any seams before adding soil; sharp cut wire needs careful handling.
Mesh specifications vary with the pest and installation. UC Master Gardeners of Orange County's raised-bed guide specifies quarter-inch hardware cloth for its gopher example. Use that as a documented example, not a universal requirement for every animal. Check local Extension guidance and the bed manufacturer's attachment instructions. Mesh does not improve compacted soil beneath it.
Scenario 4: Concrete, Patio, or Deck
An open-bottom bed is usually not the right choice for concrete, patios, decks, or rooftops unless the manufacturer specifically supports that setup and you have a drainage plan. Soil, water, and wet compost are heavy. Stained concrete and trapped water can also become problems.
A liner can retain soil, but it is not an engineered floor or an exit for water. The Orange County guide describes landscape cloth on concrete or stone, or a base with drainage holes. Maryland Extension treats hard-surface beds separately from soil-based beds. Confirm the frame or planter is suitable for the surface, then follow its drainage and support instructions. An impermeable side liner in a designed planter is a different use from sealing an open-bottom frame with plastic.
Scenario 5: Deep Beds and Cost-Saving Lower Layers
Some gardeners consider woody lower layers to reduce purchased fill. Treat this as a separate design choice with uncertain decomposition and settling, not a default recommendation for every bed above a particular height. Preserve usable rooting space for your crops. The Extension sources below do not establish a universal woody-layer recipe or certify the linked beds for one.
This is where the bottom-layer question overlaps with fill strategy. Read How to Fill a Raised Garden Bed before buying a very tall bed.
What Not to Put at the Bottom
Do not seal an open-bottom frame with an undrained plastic sheet. Do not assume a rock layer repairs a waterlogged site. Diagnose the ground and choose a suitable growing mix before spending money on a supposed drainage layer.
Avoid unknown treated scraps, painted wood, invasive weeds, pet waste, and household trash as fill.
Do not decide lower filler from wall height alone. Draw the usable root zone for your crops first, subtract any unusable ground or barriers, and allow for settlement. If a design depends on unknown decomposition or leaves inadequate rooting space, use an appropriate growing mix instead. The soil calculator estimates volume; it does not certify that a layer plan will grow your chosen crop.
Pre-Fill Worksheet
Use this planning worksheet before buying a barrier or filling the frame. These are inspection prompts, not results from testing the products above.
| Record | Your decision | Pause if |
|---|---|---|
| Surface and water route | Soil, concrete, or supported planter; where excess water can leave | There is persistent standing water or no planned outlet |
| Soil and crop plan | Usable rooting depth and appropriate soil testing or amendments | The underlying soil is unsuitable or depth is unknown |
| Barrier purpose | Turf suppression, confirmed gophers, or soil containment | One material is being expected to solve all three |
| Installation | Seams, corners, edges, attachments, and manufacturer instructions | Mesh gaps or an unsupported liner remain |
| Filling sequence | Weed preparation, barrier inspection, then measured fill volume | Vegetation has not been dealt with or the barrier cannot be checked later |
Photograph seams and outlets before they disappear under soil. Recheck the water route and growing-mix level after the first substantial rain or watering; settling and site drainage still need observation.
FAQ
Should I put anything at the bottom of a raised garden bed?
If the bed sits on safe, workable soil, you usually do not need a permanent bottom layer. Keep it open-bottom for drainage and root growth. Add cardboard only for temporary weed suppression or hardware cloth for burrowing pests.
Should I put cardboard at the bottom of a raised bed?
Cardboard is useful when placing a bed over grass or annual weeds. Use plain cardboard, remove tape and labels, overlap it, wet it, and fill the bed. It breaks down over time and is not a permanent barrier.
Should I put rocks or gravel at the bottom of a raised bed?
Usually no. Rocks take up root space and do not fix most drainage problems. Good soil structure, an open bottom, and the right site matter more.
Should I use landscape fabric under a raised bed?
Landscape fabric can retain soil in a suitable hard-surface design, but it does not provide structural support or create a water outlet. Over usable garden soil, assess whether a permanent barrier is needed before adding one.
What should I put under a raised bed for pocket gophers?
UC IPM describes wire mesh beneath raised beds for pocket-gopher exclusion. Secure the footprint, seams, and side connections. A bottom barrier does not stop aboveground access or establish protection against other animals.
Can I put logs at the bottom of a raised bed?
Only consider a lower woody layer after planning usable rooting depth, drainage, and settlement. The sources here do not establish a universal recipe. If those conditions are unknown, use an appropriate growing mix instead.
Final Verdict
For a bed over usable garden soil, start by checking whether any permanent barrier is needed. Use cardboard for a planned turf-smothering step, mesh for a documented pocket-gopher problem, and a suitable containment-and-drainage design on hard surfaces. None of those choices replaces checking soil, rooting space, and the water route.
Sources and Scope
- University of Maryland Extension: Soil to Fill Raised Beds — preparation differs for turf, compacted soil, existing gardens, and hard surfaces; read on October 8, 2026.
- UC IPM: Pocket Gophers — gopher-specific exclusion and the limits of underground barriers; read on October 8, 2026.
- UC Master Gardeners of Orange County: Raised Beds — examples of ground preparation, mesh, and hard-surface containment; read on October 8, 2026.
The worksheet is editorial advice. These sources do not certify the linked products for your site.
