If you are planning on building raised beds then you will have probably spotted the gravel boards at your local DIY store and wondered how well these would work. Can you use gravel boards for raised beds? let’s have a look and find out.
Yes, you can. Look closely at the photo above and you will even see that I built the raised beds in my greenhouse out of gravel boards.
So where does the confusion in relation to ravel boards come from? Well, similarly to decking boards it turns out there is still some outdated information online telling you not to use gravel boards for raised beds, so what gives?
Well the advice was sound at the time and still is in relation to old gravel boards, what has changed is the gravel boards themselves. Mainly I am talking about the treatments the boards receive in order to make them more resistant to the weather.
Dangerous Chemicals
It used to be that all pressure treated timber had lots of pretty nasty stuff in it. Stuff like arsenic and high levels of chromium.
This has all changed now and the pressure-treating process now uses a copper-based treatment. The older process of using arsenic has been outright banned so you don’t have to worry about buying wood that has been treated in that way by accident.
What this means is that any new gravel board is safe to use for raised beds but won’t last as long as old gravel boards used to. The new treatment, while safer, doesn’t provide as much protection.
Extending the life of gravel boards
if you do build a raised bed out of gravel boards and want to extend its life of it then consider using a plastic membrane behind the boards.
This is just a layer of plastic sheeting that goes in between the board and your soil. It will stop the board from soaking up moisture from damp soil and make it last longer.
If you do this and also extend the plastic membrane across the ground to work as a weed barrier then make sure you put some drainage holes in it! You don’t want to inadvertently make a muddy pond.
Why use gravel boards?
Well, the reason I chose to use gravel boards for the raised beds in my greenhouse is that they were simply the cheapest pressure treated board in the DIY store when I went in. They were cheaper than the equivalent sized decking board and will do the job just as well so I picked them up over a decking board.
What is a gravel board?
a gravel board is a long flat board that is intended to go at the bottom of a fence and hold gravel back, hence the name gravel board.
They also provide a separation between the bottom of your fence and the ground below. This is to help preserve the life of the fence, it is the gravel boards job to soak up all that punishment and not the much more expensive fencing panel.
Because they are designed to be used in fencing they are pressure treated to withstand the elements. This makes them perfect for use as a raised bed as they will last a lot longer than untreated timber.