If you have a DIY project that’s been sitting on your to-do list, whether a piece of unique furniture or large-scale construction, bamboo is a great material to work with. One of the rewards of growing your own bamboo is that you can harvest it yourself to use for construction and crafts. But do you need to dry bamboo poles before you start the DIY bamboo project?
There are a few ways to dry and cure your bamboo poles for construction, but all methods involve some form of air drying. If you set up your bamboo correctly to be air dried in the right location and prevent fungal growth, bending, or cracking, your bamboo poles will become useful construction material.
We’ll take a look at the different ways that you can dry and cure your bamboo poles so they are suitable for construction projects, along with other steps you can take to increase the strength and reliability of your bamboo culms.
Why dry your bamboo poles for construction?
Drying bamboo is especially important for construction because it ensures long-lasting strength and durability. Green bamboo should never be used for construction material for a couple of reasons. The first is that it is much more attractive to pests and vulnerable to fungus and mold, since it contains so much moisture.
Moreover, bamboo culms shrink as they dry. The culms can shrink by about 10-15% in diameter, and the thickness of the walls can shrink up to 17%. Therefore it’s much safer and more reliable to allow bamboo to fully dry out before using it for construction.
How long will it take for bamboo to dry?
How long it takes for your bamboo to dry depends on how you dry it and your drying setup. Drying your bamboo as quickly as possible won’t necessarily result in a great outcome if it isn’t done properly, unless you don’t mind the bamboo splitting.
Bamboo takes longer to dry than just about any other type of wood material. This is because bamboo has hygroscopic properties, which absorb and hold onto moisture. This means that, depending on your bamboo species and the season in which you cut your bamboo, it can have as much as 80% moisture content (freshly cut) – that’s a lot of moisture!
On average, air drying bamboo naturally will take 2-3 months, but some factors may extend or shorten your drying time, such as:
- The moisture content of your bamboo culms, which varies according to age and season
- How thick the walls of your bamboo are where the moisture is stored
- Your climate, especially humidity levels
- Rain and general exposure to moisture (such as from sprinklers)
- Additional processes like soaking and treating your bamboo
- Drying by air vs. with heat
- Wind and air circulation
How to air dry bamboo poles
Most of the work that goes into air drying your bamboo goes into setting up the right conditions for your bamboo to dry. After that, minimal effort is required. Without the proper setup, however, you risk your bamboo poles bending, cracking, or developing fungus, which can compromise the strength and integrity of the material.
Step 1: setting up your air drying space
Before you cut down your bamboo poles, it’s important to have the proper space ready to air dry them. The first key element you’ll need is air circulation: you want to avoid stagnant air at all costs because this is a breeding ground for fungus.
Next, you’ll want to ensure that your bamboo is protected. You’ll want some form of protection from direct sunlight, but especially rain. Ideally, this would be in a garage, storage unit, or even a well-ventilated barn. If you have no other options, you can set up a tarp, but you’ll have to find a way to prop it up over your bamboo so it isn’t sitting directly on top of it, which would trap moisture.
Make sure that your bamboo won’t be lying directly on the ground either, especially directly on soil, as this will also trap moisture and lead to mold or fungal growth. Instead, use a rack to dry the bamboo or lean them against a wall (depending on how many poles you are drying at a given time). If needed, you can stack your bamboo poles, but make sure not to stack them too high because they can crack under weight while still green.
Step 2: harvesting and stacking your bamboo
When harvesting timber bamboo, it’s key to only harvest culms that are mature enough to be used for construction. It’s best not to harvest bamboo until it is at least three years old. It’s also best to harvest your bamboo in the fall and winter months, when the weather tends to be a bit drier. This will help reduce the moisture content of the culms and allow them to dry faster.
Once harvested, the best way to lay out your bamboo is to stack them vertically with the help of separators. If you want to stack them horizontally you can, but the best way to do this is to alternate directions with each layer of bamboo. This will help increase airflow and also will help to prevent bending poles under stress.
Step 3: rotate and monitor your bamboo
Once your bamboo poles are stacked and ready to dry, all you need to do is monitor your bamboo closely and rotate the poles every 1-3 weeks. This helps to increase the drying efficiency, but it also ensures that your bamboo poles don’t warp or bend from sitting stagnant.
While drying, be mindful of fluctuations in humidity and temperature which can produce additional moisture. Check on your bamboo poles regularly for signs of mold, and if you spot any signs of mold or fungus on a pole, be sure to remove it immediately to keep the spores from spreading to other culms. It can take up to 2-3 months for the bamboo poles to dry completely.
Optional: when the bamboo is dry, some people like to let it sit in the sun for a week to allow the bamboo to change to a golden yellow color because they love the aesthetic.
How to dry bamboo poles with heat
You can dry bamboo using heat, although this process is more complicated than simply air drying. Some people believe heat drying bamboo is much more effective since you have more control over the environment. However, others insist that this is the worst way to dry bamboo for construction since it increases the risks of cracking your bamboo poles.
As such, this method works best for bamboo poles that have already been split, but it is still possible to dry whole bamboo poles if proper precautions are taken.
Step 1: heat method and safety
Whether it’s a kiln or a charcoal fire pit, you’ll want to ensure that your heat source is equivalent to 250°F (122°C). Regardless of the type of heat source you choose, you must set up your bamboo so that it will not touch the heat source directly.
You must also constantly monitor your bamboo to ensure that the culms don’t catch on fire. Using a grill and a drying rack is one way to do this. Make sure that safety cautions are taken at all times, including wearing fire-resistant clothing and safety goggles to protect your eyes.
Step 2: wiping the oil
Bamboo contains oils known as resins, which help to preserve the canes. When you heat bamboo, the resins will rise to the surface, and once it does the culm can be wiped down. Wiping the resins is said to seal the bamboo, but at the same time helps to wick the moisture out of the culms.
Step 3: drying and cooling
Once the bamboo has changed color from its usual dark green to a lighter green or yellow, remove it from the heat source. Set it aside in a protected, well-circulated area to air dry for 2-3 weeks.
Step 4: inspect your bamboo
Heat-dried bamboo runs a higher risk of getting damaged, cracked, or snapped. Make sure that once your bamboo is fully dry that you inspect it before using it to ensure that it still has structural integrity for the job.
Do you need to soak your bamboo poles before drying?
It may seem counterproductive but there is some sense in this, believe us. Soaking bamboo in water is often part of the treatment and curing process, but you may also add this step to increase the effectiveness of drying your bamboo. It takes a bit longer since it’s an additional step, but it can result in stronger bamboo that is ideal for construction material.
There are some benefits to soaking your bamboo before drying it. First, it helps to protect the culms from pests since soaking removes starches from the poles, which pests love to devour. It also ensures that your bamboo poles are evenly moist. Therefore it will also dry evenly and will reduce the risk of cracking or splitting. This is ideal for construction since strength and reliability are the most important.
Learn more about the process of soaking your bamboo here!
FAQ about drying bamboo poles
How do you know when your bamboo is fully dry?
When your bamboo is no longer green and has turned a light, faded green to a golden, tan color, you will know it is thoroughly dried out. Your bamboo poles will also have shrunk in size.
How is curing/treating bamboo different from drying it?
Many people call the drying process by many names: curing, drying, even treating – so what’s the difference? Drying bamboo refers to the process of allowing the moisture to evaporate from the bamboo, and is used in both curing and treating.
However, there are slight differences between the curing and heating. Curing typically refers to allowing the bamboo to dry over a period of time or with heat to preserve it naturally, while treating usually refers to soaking the bamboo in salts or chemical preservatives first, with longer-lasting results.
What does bamboo fungus look like?
While your bamboo is drying, keep an eye out for fungus. Fungal spots range from round, black and gray patterns on the culms to mosaic-like patterns. Mold can range from dark black to light green or even white. If you spot poles with mold or fungus, it likely means there’s too much humidity. In this case, increase the airflow and remove poles that are too infected to be of use in construction.