Four or five years ago I had this crazy idea to burn our existing garden boxes. My hope was that it would preserve the wood, as we had opted to save some money and use construction grade lumber rather than cedar or redwood.
I blogged about that here.
That post has been popular ever since, and I get lots of questions about how they have held up. The answer is that while we eventually dismantled that garden, the wood held up surprisingly well. Even after we took them apart I stacked the wood to the side and it continued to withstand the elements.
That’s pretty impressive, given the fact that I burned them in place and not all that thoroughly.
So this year I decided to do a proper job of it.
We built three garden boxes, each about 20 feet long by 5 feet wide. That’s a lot of dirt. And a lot of wood to burn. While shou sugi ban, the Japanese wood burning technique I’m using here technically refers to burning cedar – and it does work great on cedar – I’m taking liberties and burning construction grade douglas fir. Because that’s what we have here.
The benefits of doing this are two fold: 1. It costs a lot less than purchasing more expensive woods that are typically used for garden boxes. Here, that’s mostly cedar and redwood. 2. The burning preserves the wood naturally, protecting it from the elements and from insects.
Here’s a look at the process:
The process of burning the wood is fairly straight forward and simple. Here’s an overview, starting with a short list of what you’ll need.
Materials and Supplies
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How to shou sugi barn garden boxes
Okay, shou sugi ban is not necessarily a verb, but let’s roll with it.
Regardless of the size of your garden, burning the boxes is a big job, so don’t get one of those tiny torches. Get a propane tank and a larger igniter/flame thrower thing. Harbor Freight has one cheap.
It is easiest to burn the wood before assembling the boxes. Be sure you are set up somewhere safe, with a water supply and hose nearby. We burned ours in the spring on damp grass and had no problem at all. I would not try this same job when it was dry, however. The problem is not that the wood will catch, but things around it. Be smart, be safe.
Give the wood a good deep char. You may need to go back over it. Wood has a high moisture content (particularly the construction grade stuff you get a big box stores), and it will take a lot of heat. Aim to get it to a alligator skin type texture if possible. It won’t take long to get the feel for it. Burn both faces, the sides, and the ends.
Scrub the garden boxes
After burning get a scrub brush and scrub it all. It will feel like you are removing a good amount of the char, but scrub them up. It is a good idea to go back and repeat the burn and scrub process a second time if you are up for it.
Look at those boards all burned and ready for oiling!
Seal with oil
After some research I chose to seal the wood with tung oil. The stuff you get at the home improvement stores isn’t the greatest. So spring for the stuff I linked or head to your closest Woodcraft or Rockler. Brush it on, run off the excess, and ba-da-boom, you are done.
Assemble the boxes and get gardening.
Over time the nice, bright clean black does give way and get dirty. But, well, it’s a garden.
To give you a little idea of how these wear, this photo was taken in June. The boxes were constructed in March.
Here’s the boxes again three months later. (With a shiny new fence!)
You can see that they really don’t look any different. I don’t expect that to change much at all over time. I may add a ledge or build on after time (our boxes are very basic since they are so large), but I have no plans to repeat the burning process.
I’m happy to answer questions about how these hold up over time. Given that we have already had a trial run I don’t expect any problems, but feel free to check in if you are interested!