Raised Garden Bed Bottom: What Works, What Doesn’t, and How to Get It Right

When you build a raised garden bed bottom, the base layer that supports soil and controls weeds and drainage in elevated garden structures. Also known as a garden bed base, it’s not just a floor—it’s the foundation that determines whether your plants thrive or struggle. Too many people think a raised bed is just a box filled with dirt. But if the bottom is wrong, you’re setting yourself up for waterlogging, weeds, or even root rot.

The right raised garden bed bottom, the foundational layer that manages water flow and blocks invasive roots and weeds. Also known as a garden bed liner, it’s not about fancy materials—it’s about function. Most experts agree: a layer of landscape fabric, a permeable textile used to suppress weeds while allowing water and air to pass through. Also known as weed barrier fabric, it is the gold standard. It stops couch grass and bindweed from creeping up from below, but still lets water drain. Skip the plastic. It traps moisture and kills soil life. Skip the cardboard too—it breaks down too fast and turns into a soggy mess by midsummer.

Drainage is just as important as weed control. If your bed sits on compacted clay or concrete, water has nowhere to go. That’s where garden bed drainage, the system or material that allows excess water to escape from a raised garden bed. Also known as bed underdrainage, it comes in. A few inches of coarse gravel or crushed stone under the fabric makes a huge difference. It’s cheap, it lasts, and it stops roots from sitting in water. You don’t need a French drain unless you’re on a slope. Just a 2- to 3-inch layer of 3/8-inch stone does the job.

Some folks swear by cardboard or newspaper under their beds. But if you’ve ever tried to dig through a wet, rotting layer of cardboard after a rainy spell, you know why that’s a bad idea. It turns into a slimy, anaerobic trap that invites slugs and slows root growth. The same goes for thick layers of mulch at the bottom—it looks nice, but it decomposes unevenly and creates air pockets that dry out roots.

What about raised beds on patios or driveways? Then you need a different approach. Use a liner with drainage holes, or elevate the bed on bricks to let water escape. Some gardeners use recycled plastic grids designed for drainage—those work well if you’re planting shallow-rooted herbs or lettuce. But for tomatoes, carrots, or root veggies, you need depth and real soil contact. That means a good base isn’t optional—it’s essential.

You’ll find plenty of advice online about lining raised beds with plastic, using geotextile, or even lining the sides with metal. But the truth is simple: the bottom layer should breathe, drain, and block weeds. Nothing more. The posts below show real results from gardeners who’ve tried every trick—from gravel to old carpet—and settled on what actually works. You’ll see how to layer materials for different soil types, how to fix a bed that’s already waterlogged, and what to avoid if you want healthy plants without constant maintenance.