Can L Use Prefinished Siding For Raised Bed Garden

Raised bed garden made from pressure treated lumber — Rot resistant lumber can be used for a raised bed garden, but not fiber cement siding.

Can fiber cement siding, such as HardiePlank, be used to make raised beds for a garden? -Ernie

All kinds of creative items can be used to make raised bed gardens, including siding and repurposed materials. While I've seen fiber cement siding suggested as a raised bed material, it doesn't strike me as a durable product for holding back heavy, wet soil.

In my own yard a few years ago, I put fiber cement siding to use in the landscape as a flexible form for a curved concrete porch, and also to hold soil back temporarily during a grading job. It worked great for my short-term purposes, but by the time I pulled it out a few weeks later, it was beginning to get soggy and crumbly and was a mess to get into the trash. The longer the fiber cement stayed in the ground, the more it fell apart.

HardiePlank and other types of fiber cement siding have a few points against them when planning a raised vegetable bed:

Wood Pulp: Fiber cement siding is a mixture of cement, silica, and cellulose (wood) fibers. Like any other product containing wood that isn't rot resistant, it will eventually break down in contact with wet soil.
Ground Contact: While fiber cement siding is made to shed water, it's not designed to be buried in wet soil. Most manufacturers of fiber cement siding, and many building codes, recommend keeping the siding at least 6" off the ground.
Flexible: Fiber cement siding is also very flexible, so you would need lots of reinforcement to keep it from bowing out from the weight of the soil behind it.
Brittle: Even though fiber cement siding contains cement, it's very fragile until firmly attached to a flat surface. If you've ever worked with fiber cement siding, you know that it's easy to snap in two. The edges of your bed would not stand up to foot traffic. And I'd imagine that an accidental kick, or bump with the lawn mower, could cause damage as well.

Cement Backer Board Alternative

As an alternative to fiber cement siding, you might have better luck with cement backer board, which is used as backing for ceramic tile. It's made with fiberglass fibers, rather than wood fibers, and would likely hold up much longer, although it would have to be cut to size.

Julie