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.
I have to disagree that HardiPlank will eventually break down in wet soil. In numerous supply houses I have been in that sell Hardi products, I have seen displays of it submerged in water for years with no swelling, crumbling or any other adversity. I have installed mosaics with it and embedded them in concrete patios with no problems. That was four years ago. While Hardi products are not designed to be used as garden planters, I believe that you have discredited their abilities and function concerning water exposure.
I have a camp I am building that has porches all the way around the house. Would Hardi Board sheets be suitable to use to cover the under side of these porches/
I WOULD NOT use hardi board for a raised bed due to wood cellulose component. In fact, I wouldn’t use hardy plank siding on a house or anything. for the same reason because it has failed and there are quite a few class action suits plus private suits. I personally have seen it fail on a 5 yr old house. On one of those class action suits – they lost in Nov 2017 Millions in fines etc. It is public record – can read the articles or look up the cases at your local library or online. Who wants to pay more for a supposed premium product on a new house have it fail 2-3 yrs in. If anyone believes it is a good exterior product – they work for the company, or are a distributor or a contractor with it on a bunch of houses. They should all be sued for ripping people off. But the issue begins at the head of the snake.
I would use Durarock cement board or Permabase cement board – (the 2nd by testing is supposed to be even more moisture resistant. Not by much but if you can get cheaper than big name Durarock I would try it. All I have used is Durarock. These are cement, aggregate (stone) and glass or wire mesh. Nothing to crumble. I had it on my back porch covering a generator 20 yrs – snow, ice, rain – no issues. Same for a planter box on top of the ground – as long as one side can breathe. If you go over 12” I would cut it in 6” or 12” widths so water can drainmout the sides in case of heavy days long rains. You could also drill holes along the sides or towards the bottom. You don’t need but 2-3 per side but will have to cover holes with row cover cloth or fine screen to keep dirt from washing out holes. If you live in low rain areas you won’t need to do.
Just make sure it is cement (no wood or cellulose). Hope that helps someone.
Fiber cement makes outstanding raised beds….if you paint it with 2 coats of first class exterior acrylic latex paint. My entire garden is raised beds made with hardie board siding and not a single one has failed in over 10 years. And the paint still looks great too.