How to Weatherproof Untreated Wood Naturally and Cheaply
Updated: Jun 10
This post contains affiliate links. If you use these links to buy something we may earn a commission. Thank you.
There are many ways to weatherproof wood, but most of them do not last. You can apply polyurethane, varnish, lacquer, linseed, Tung oil, or a combination. However, none of these methods last more than 2-10 years (depending on the method and how well it was maintained). Also, these methods can become pricey if you’re trying to weatherproof a large amount of wood. These methods may work well for some outdoor furniture but are not a good option for something like raised garden beds, a fence, or siding for a structure like a shed or even a house.
Did you know that you can char wood to weatherproof it? Charring all surfaces of the wood actually weatherproofs it for up to 80 years! This method comes from Japan and is called yakisugi method or shou sugi ban. Traditionally it refers to charing either cypress or cedar wood over an open fire and then coating the wood in a light layer of oil. However, this method will work with any kind of wood and does not require oil.
Personally, I love this method. It's cheap and easy, and I love the look of the black wood.
Recently, I used this method to build a fence around my garden. We tore down an old shed in our yard about 2 years ago. We saved as much lumber as we could from the building, and have kept a good size stack in our yard under tarps since then. While we have had plenty of outdoor projects requiring lumber, we were hesitant to use the wood outdoors because it’s untreated and would rot after a few years. And then I learned about the shou sugi ban method! We were building the fence soon after!
There are 2 ways to char lumber, using a propane torch or over an open fire.
Wanting to do this project as cheaply as possible, I initially charred the wood over an open fire. Our fire pit made this job easier, as I could set the wood up on the edges of the fire pit over the fire, and not set it directly in the flame. I did a large amount of lumber that day, but the overall process actually took me less time than I expected.
To char wood over an open fire:
1. Build a healthy fire. Do not let the fire get so large that you cannot stand close to it. I would recommend waiting for a cool damp day.
A fire pit with stone or brick walls makes this job easier, as you can slide the board across the top of the pit without setting it directly in the flame.
2. Place the end of the wood directly over the fire, and leave it for 2-3 minutes. Watch closely, turning the wood occasionally to check the color. The wood needs to turn solid black. Once the wood is black, rotate the wood and do the other side.
3. Once the end is solid black on all sides, slide the wood down and do the next section.
4. Repeat this process until you only have enough un-charred wood left to hold on to without burning your hands.
5. Set the wood aside (sawhorses would be helpful), and wait until the wood is completely cooled. I set it on the grass as the grass was damp that day.
6. After about 15-20 minutes, the wood should be cooled. Pick it up by the charred end, and burn the other end.
Be sure to be safe! If you have a burn ban in your area, do not burn! A fire pit or designated burn area is best as it prevents fire from spreading. I chose to do this on a damp day and kept the fire inside our fire pit. I live in an area that gets plenty of rain. Keep a hose or fire extinguisher nearby in case of emergency.
Heavy work gloves are helpful to prevent burns and splinters. I did not wear gloves, but luckily I did not burn myself. I did however get a few splinters as the wood I was working with was in rough shape.
I only burned 8 ft long 2x4s and 2x3s. Anything longer or heavier than this may make the job difficult. I later had 4x4s to char, and found I could not maneuver them well enough to do the job effectively over an open fire…
Hence, the purchase of the propane torch.
To use a propane torch to char wood:
1. Carefully read and follow the instructions for using the propane torch.
2. Place your wood carefully so that it’s not laying down on something that can easily catch fire. A patch of dirt, concrete, or gravel would work. You can also lean your wood up against something that will not catch fire, or set it in the ground.
3. Using the propane torch, fire the wood until it’s a solid black color. Be sure to get all sides that will be exposed to the weather.
This works best on wood that is thoroughly dry. Wood that is damp or still green will not burn evenly or well.
Here is the propane torch I used:
We used this method to build our garden fence, and we like this method so much that we plan on using it for many future projects! The purchase of the propane torch makes the job so much easier! It is more costly, as you have to purchase both the torch and the propane, but if you’re like me, you’re always doing an outdoor project, the torch will be an excellent addition to the toolbox. In the future, I plan on using the shou sugi ban method to weatherproof raised beds. It would also be useful in larger builds such as a chicken coop, dog house, garden shed, or any other number of builds! Have you ever used this method? Would you ever use it? If so, tell me your experience in the comments!