We have some old firewood on the side of our house and we were wondering if it’s okay to burn it. It seems okay, but I did some more research to find out more. Here’s what I found.
According to the CSIA, firewood that is seasoned (dried) lasts about 3-4 years before it loses efficiency in burning. Firewood lasts longer if it is properly seasoned and stored. For the best seasoning, firewood should be cut and split after felling. Store it outside, covered, and off of the ground to avoid rotting.
Even though firewood lasts several years, how can we tell if it goes bad, and is it okay to burn? Let’s take a closer look.
Want an easy way to check if your firewood is seasoned? I recommend using a firewood moisture meter. Here’s the moisture meter I use from Amazon.
How To Tell if Firewood is Bad
|Good Firewood||Bad Firewood|
|Solid wood||Has holes or is crumbling|
|Has 20% or less moisture||Moldy|
|Burns longer||Burns too quickly|
You can tell if firewood is bad if it’s rotting and crumbles with little effort. At this point, the firewood is deteriorating into dust and possibly infected with mold or insects. The most common reason firewood goes bad is if it’s stored on the ground or in a wet place.
The good news is that once firewood is seasoned it lasts at least 3-4 years and sometimes indefinitely. This is because a moisture content of 20% or less prevents fungus and bugs such as termites from taking hold. Storing in a dry place and off of the ground also improves its lifespan.
You can tell if firewood is good and seasoned with 3 methods.
- Visual – Seasoned firewood has cracks forming and is lighter in weight (due to the loss of water). Firewood that is still good is solid and not falling apart.
- Sound – Good and seasoned firewood has a ringing sound when two pieces are hit together. Unseasoned firewood has a dull thud sound as its water content absorbs the sound.
- Moisture – The best way to confirm if firewood is good is with a moisture test. Firewood should be seasoned until it has a moisture content of 20% or less. You test this with a moisture meter. For example, I use this firewood moisture meter on Amazon.
Ideally, only burn good and seasoned firewood as it burns cleaner, hotter, and longer.
Seasoned firewood is when firewood is dried to have a moisture content of 20% or less. This typically takes around 6-12 months but varies on the type of wood and how it’s cut. Firewood that is split into quarters seasons the fastest.
Unseasoned or “green” firewood is wood that was recently cut from the tree and has 60% or more moisture. This not only makes it more difficult to light but produces much more smoke and creosote (the harmful tar buildup you see in chimneys).
Recommended: What is Seasoned Firewood? (Explained)
Is it Okay to Burn Old Firewood?
Old firewood is safe to burn as long as it doesn’t have mold, fungus, or bugs. However, firewood that is too old and dry burns too fast and hot. This doesn’t make good firewood and can damage masonry from the excess heat. You can tell if your firewood is too old and dry if it has a moisture content of less than 10%.
While firewood over 3-4 years in age is usually too dry and considered “old”, I don’t recommend disposing of it automatically. For example, first check it visually to see if it’s still intact and not falling apart. Next, use a firewood moisture meter to check that its moisture content is between 10%-20%.
If you do find your firewood is still good, rotate it towards the front of your pile so you burn it sooner.
However, if your firewood is too old and has moisture under 10%, consider putting it aside for an outdoor fire pit or composting it. Firewood that’s too old and dry also makes great kindling since it catches easily.
Also, avoid burning treated wood or driftwood as it has contaminants and is released into the air.
Is it Okay to Burn Rotting Firewood?
Rotting firewood shouldn’t be burned as it likely has mold or fungus, which is released into the air when burned. It also burns extremely quickly and doesn’t make good firewood. While some people burn rotting firewood outdoors, it’s not recommended to burn it indoors or in an enclosed space.
Other than mold, a problem with rotting firewood is that its material is breaking down and has little moisture content. Similar to old firewood, rotting firewood burns too fast for it to make good wood. The primary reason to burn rotting wood is to simply dispose of it.
Most times, you can tell if your firewood is rotting or infected by inspecting it visually. If it has many holes or is crumbling, the firewood is rotting. Also, you might be able to see blue or white mold on it.
There’s also a good chance rotting firewood has bugs in it. While this typically isn’t a problem for outdoor fireplaces or fire pits, it’s not a good idea to bring rotting firewood indoors.
To help prevent critters from visiting your home, it’s best to store firewood at least 10-20 feet from the house.
If you have rotting firewood and you decide not to burn it, it’s amazing to use in compost piles for your garden or as hugelkultur mounds. We used some of our old firewood logs as hugelkultur for our raised beds last year and we had some of the best tomato yields!
How Long Can Firewood Be Stored?
After taking about 6-12 months to season, firewood lasts at least 3-4 years. If stored well, it lasts definitely. For the best storage, keep your firewood in a covered shed with some exposure to wind and sun if possible. This helps season the firewood and preserves it.
Once firewood is seasoned and has below 20% moisture content, it’s too dry for the liking of mold and most bugs. As long as it’s stored in a dry place off of the ground, it’ll last for a long time.
More Tips to Store Firewood
The best place to store firewood is in a covered shed. The second best place is on a firewood rack with a cover. Only cover the top of the firewood pile to protect it from the rain and snow. This also allows airflow to reach its sides.
After cutting firewood, split it into quarters as soon as you can. This increases the surface area of the inside of the firewood to dry out and minimizes the surface area of the bark. Since bark naturally protects the wood from moisture and fire, having less of it speeds up the seasoning process.
Stack firewood bark-side down except for the top row. This allows the top and the sides to dry out quicker. Placing the top row bark-side up gives the top of the wood a natural protectant against moisture such as rain and snow.
It’s common to store firewood in advance to allow it to season for at least 1 year before burning. Many people store 2-3 years worth of firewood so they only have to worry about it every few years. Ideally, burn the oldest firewood first to prevent firewood from expiring.
Firewood stored indoors and outdoors lasts the same amount of time as long as it’s off the ground and in a dry place. However, firewood seasons faster outside because of the sun and wind drying out the wood. While seasoning normally takes 6-12 months, it can be as fast as 3 months in certain conditions.
To see more about the pros and cons of storing firewood inside vs outside, check out my other post: Should Firewood Be Stored Inside or Outside? (Answered).