Wet Firewood

What Wet Firewood Is (And Why You Shouldn’t Burn It)

In Firewood by James O'KellyLeave a Comment

Burning wet firewood can cause both short-term and long-term issues for your fireplace or stove and so it’s never recommended to burn wet wood.

It can sometimes be difficult to tell the difference between firewood that is dry and firewood that is too wet to burn. Wet wood can have a few traits that helps distinguish it from dry wood, so what is wet firewood?

Wet firewood is wood that is too high in moisture content to burn efficiently in a fireplace or stove. Wood that is too wet to burn can struggle to catch fire, produce more smoke, release less heat and create an overall unpleasant burning experience.

To help you have the hottest and most successful fires it’s important to understand how burning wet wood can affect all stages of having a fire.

We’ve therefore put together this complete guide to burning wet wood to explain what it is, why burning wet wood is bad, the problems caused with burning wet wood and what you can do to make sure that you’re only burn wood that is dry enough.

What Is Wet Firewood?

Not all forms of wood are suitable for use as firewood. In order for wood burn effectively and efficiently in fires it must have the right properties, including being low enough in moisture content.

Wood is naturally high in moisture, and a large majority of wood can be made up of moisture content.

If you take a freshly cut branch or log and test its moisture content using a moisture meter you’ll be able to see that it will be relatively high in moisture.

Green Wood Moisture Content
Unseasoned wood will be too wet to burn

Not all wood will have the same moisture content however. The moisture content of wood can be influenced by:

  • The time of year the wood was cut.
  • The type of wood.
  • The species and health of the tree.
  • Whether the wood has had time to dry before being tested.

One of the biggest factors that can affect how successful a fire is can be the nature of the firewood being burnt.

High moisture content will not burn well on a fire. A fire will need to use more of its energy to burn off the excess moisture within the wood before the firewood can be properly combusted.

When wet wood is burnt it can lead to short-term issues such as struggling fires and more smoke being produced, as well as longer term issues such as increased creosote buildup within chimneys.

If wood is to be used as firewood it must dry enough so that it doesn’t cause a fire to struggle. Incomplete combustion of wood due to struggling fires can lead to increased smoke and creosote production.

Wet firewood is therefore wood that is too high in moisture content to burn effectively, resulting in poorly burning fires with incomplete combustion, producing more smoke and creosote, and releasing less heat.

It’s important to identify when you’re burning wood that is too wet and so we’ve explained throughout this article how you can tell whether your particular firewood is dry enough to burn without causing issues.

What Is Classed As Wet Wood?

Wet firewood can be one of the main reasons why fires struggle to catch and keep going. Dry firewood is able to burn much more easily and will lead to hotter and more successful fires, but what is actually classed as wet firewood?

Wet firewood can be classed as wood that contains over 20% moisture content.

The Environmental Protection Agency (EPA) states that firewood with a moisture content within the 15 to 20% moisture range burns the most efficiently on fires.

It’s also generally recognized within the industry that once wood has reached below 20% it can be considered to be ‘properly seasoned’ firewood, and therefore suitable for burning.

20% moisture content can therefore be considered as the cut-off point between wet firewood and dry firewood.

At 20%, firewood contains a low enough amount of moisture that a fire won’t struggle to burn it, but also retains enough moisture that it won’t burn too quickly and be an inefficient source of heat.

As the moisture level of firewood increases above the 20% threshold it becomes progressively harder to burn. For wood that contains more moisture a fire must use more of its energy to burn off the excess water within the wood before it can be properly combusted.

Will Wet Firewood Burn?

Depending on how high the moisture content of the firewood is and whether the whole piece of wood is wet or just the outer layers, wet firewood will either struggle to burn or not burn at all.

Wet firewood closer to the recommended 20% moisture content level can be harder to burn compared to firewood under 20%.

Very wet firewood, typically freshly cut unseasoned ‘green’ wood, may not be able to catch fire and burn at all. It can be very hard to start a fire using very wet wood, while adding a high moisture content log to a fire can also cause it to go out.

In what form firewood is wet can also influence whether firewood will still burn if wet.

Unseasoned firewood will still be higher in moisture content throughout, and burning wet unseasoned firewood will be a bigger cause of fires struggling and producing more smoke.

Seasoned firewood that has simply got wet due to rain will only typically be wet on the outer layers of the wood. Burning wet seasoned or kiln dried firewood can therefore not be as bad as burning unseasoned wood.

Why Is Burning Wet Wood Bad?

It’s not recommended to burn wood that is too high in moisture because of the number of issues that can be caused as a result of doing so.

Burning wet wood can be bad for both fires and fireplaces or stoves because of the byproducts produced from poorly burning fires. A fire can release more smoke and creosote when excess moisture in wood causes incomplete combustion.

Increased production of creosote can lead to increased build up within the insides of your chimney or flue over time. This can lead to needing to have your chimney swept more often than usual as well as a number of other issues associated with creosote that you can read more about here.

A chimney lined with too much creosote can also cause a reduction in draft on your fireplace or stove, and in very extreme cases can cause chimney fires.

The main problems associated with burning wet wood are:

  • It will be harder to get the wood to catch fire.
  • It will be harder to keep a fire going.
  • The fire can produce more smoke.
  • More creosote can be released by the fire due to incomplete combustion of the wood.
  • Creosote can build up within the chimney or flue leading to a reduced draft or the potential for chimney fires.
  • A chimney or flue will require more frequent cleaning due to increased creosote production.
  • The fire can make hissing noises as the excess moisture is burnt off.
  • Less heat produced by the fire.
  • Can take a longer time for a fire to heat up to operational temperatures.
  • The fire won’t be able to produce a clean burn and more pollutants can be released into the atmosphere, adding to local air pollution.
  • The fire will be far less efficient overall compared to burning properly seasoned and dry firewood.

All of these can be the effects of burning wet wood in either a fireplace or stove.

How To Tell If Firewood Is Wet

Firewood that is too wet to burn will be harder to light and harder to keep burning, and may produce more smoke than usual. Wet firewood can have moisture visible under the bark or feel wet to the touch, and will have a moisture content level higher than 20%.

Before burning any new stack of firewood it’s important to understand what properties the wood currently has and how it will perform when burnt.

To check whether your firewood may be too wet to burn you can:

  • Check the firewood for any visible signs of excess moisture.
  • Use a moisture meter to confirm the actual moisture level of the wood.
  • See how small pieces of the wood perform on a fire.

Wet Wood vs Dry Wood

To see if your firewood is too wet to burn, in the first instance you can check the wood over for any visible signs.

Wood that is too wet to burn can:

  • Be moist to the touch.
  • Have moisture visible under the bark or in the center or the log when split.
  • Be heavy. Properly seasoned and dry wood will be lighter than unseasoned wood
  • Be greener or darker brown in color.
Green Wood
Unseasoned wet wood

You’ll want to be burning only properly seasoned or kiln dried firewood that:

  • Is light in weight.
  • Dry to the touch.
  • Has no moisture visible throughout the wood.
  • Course looking at the ends that may have cracks.
  • Has bark that can easily come away on one piece.
Seasoned Firewood
Well seasoned and dry firewood

Checking The Moisture Content

The best way to understand how your firewood will behave on your fires is to use a moisture meter to see the actual moisture content of the wood.

If you don’t already have a moisture meter we highly recommend getting one (see our recommendations here.). It allows you to see the exact moisture percentage of your wood and can give the best indication of how well it will burn.

We have a complete guide on how to check the moisture content of your wood using a moisture meter, but you essentially need to press the prongs on your meter into the wood in order to provide a reading.

It’s generally recognized that wood with over 20% moisture content is too wet to burn.

Wet Firewood
This log is currently too wet to burn as it contains over 20% moisture

If your firewood is reading over 20% moisture then look to season it for a while longer until it’s dry enough to burn efficiently. See our guide on how to season your own firewood for more information.

You don’t want to be burning wood that has a much higher moisture content than 20% as it will become progressively harder to burn and lead to all the issues we’ve outlined in the article such as more smoke and creosote production.

Firewood that reads 20% or less moisture content is what you want to be burning.

Dry Firewood Moisture
This log is under 20% moisture and therefore ready to burn

Testing The Wood

You can also use small pieces of your firewood in a fire to see how well it performs.

If your wood is too wet to burn:

  • It can be hard to catch fire.
  • Struggle to keep burning.
  • More smoke can be produced than usual.
  • A musty wet smell can be apparent.

Will Wet Firewood Dry Out?

Wet firewood will be able to dry out. If firewood is wet because it hasn’t been seasoned for long enough then it must be air dried or kiln dried in order to reduce its moisture content. If firewood is wet because of rain then it should be air dried for a short while until the moisture level returns to normal.

We’ve explained the best way to dry out your wet firewood below.

How To Dry Wet Firewood

To dry out wet wood for burning stack the firewood in a row in an open location that benefits from the wind and sun. Keep the stack of seasoning firewood off any moist ground, and located under a suitable form of cover if located in a wetter climate.

If your firewood is too wet to burn then you’ll need to leave it to season for a while longer. Seasoning is the process of naturally air drying the wood until it has reached a low enough moisture level for it to burn effectively.

Utilizing the sun and wind to naturally dry out your firewood is the best way to get your wet firewood ready for burning.

Whether your wood is still unseasoned or has got wet due to rain, the best way to stack and dry out your wet firewood quickly is to:

  • Choose a location for the firewood that is open to both the prevailing wind and the sun.
  • Stack the firewood in a single row leaving enough of a gap between the logs to cater for airflow.
  • Keep at least one side of the stack completely open to the atmosphere.
  • Keep the wood off any moist ground on either a dry platform or raised up on treated timber.
  • Provide a suitable cover over the firewood in the form of a roof or lean-to/overhang if located in a wetter climate.
How we season our firewood

For more information on how to dry out firewood we have a complete guide to stacking and seasoning firewood.

Wet Firewood

Firewood Wet From Rain

If your firewood has got wet from the rain then look to leave it in a dry location for up to a week until the excess moisture has been removed from the wood.

When dry firewood is rained on it can penetrate the surface layers of the wood so that they become damp. The whole area of a log typically won’t become completely moist due to rain but it can be enough to cause the wood to burn inefficiently on a fire.

It’s therefore important not to burn wet firewood due to rain even if it has been fully seasoned.

However, wood wet as result of rain will dry much faster than unreasoned wood and so it simply needs to be left outside in dry conditions and it will be able to return to normal moisture levels within a couple of days.

Rained on firewood can be stacked outside as you would do for seasoning firewood, but can also be placed in another form of shelter such as a wood rack.

Firewood Shed
Leave wet wood to dry off in a dry place such as a wood rack

How Long Does It Take For Wet Wood To Dry After Rain?

It can take a couple of days or up to a week for wet firewood to dry after rain.

The actual time it takes for wet wood to dry out after rain can depend on how long the firewood was exposed to the rain and how effective the air drying process is.

Firewood subjected to prolonged contact with rain can take a longer time to dry out compared to wood that has experienced a short amount of light rain.

Firewood located in an open dry area outside, and off the ground and with sufficient cover will dry faster than firewood that isn’t properly exposed to the wind and sheltered from further contact with moisture.

Use a moisture meter to check the progress of your drying firewood every couple of days.

Does Burning Wet Wood Cause Creosote?

Burning wet wood can cause increased creosote production because of incomplete combustion of the firewood. As the moisture level of firewood increases the amount of creosote being produced by the fire can also increase.

Creosote is a black tar-like substance that can be found lining the internal walls of your chimney.

Creosote is a byproduct of wood fires that is released when incomplete combustion of the wood occurs.

Incomplete combustion of firewood happens when there’s an issue with either the fuel or the air supply to the fire.

In this case, wet wood can lead to incomplete combustion of firewood and therefore creosote being released. Incomplete combustion of wet wood occurs because more energy is required by the fire to burn off the excess moisture before the firewood can be burnt effectively.

This means that the higher the moisture content of the wood the more a fire can struggle to combust it, and therefore the more creosote can be produced.

Over time creosote can line your chimney and lead to issues such as a reduced draft and potentially dangerous hazards such as chimney fires in even more severe cases. You’ll also need to have your chimney swept much more often to help minimize the risk of these problems occurring due to burning wet firewood.

Ensuring that you’re burning only properly seasoned firewood with at most 20% moisture content will help to reduce creosote production to a minimum and keep your fireplace or stove clean and safe.

Does Burning Wet Wood Smell?

Wet wood can produce a musty smell when burnt. The increased production of creosote from burning high moisture content wood can also create a lingering tar-like smell from your fireplace or stove.

When wet firewood is used on a fire the excess moisture within the wood needs to be burnt off before the wood can be properly combusted.

This moisture will be released as steam and may cause the internal walls of your chimney to be become damp over extended periods of burning wet wood.

Wet wood can therefore cause a musty smell in both the short-term and long-term, where you may notice a damp smell during your fires as well as from your fireplace or stove when they’re not in use.

Burning wet wood can also lead to increased creosote production from your wood fires as a result of incomplete combustion. Creosote has a tar-like smell and can buildup and line your chimney or flue over time.

The more wet wood you’re burning the greater the build up of creosote within your chimney or flue can be.

If you’re burning wood that is too wet you may need to have your chimney swept more than the recommended once per year in order to combat both the smell and the other issues caused by increased creosote production from your fires.

Why Is Burning Wet Wood Bad For The Environment?

Burning wet wood can be bad for the environment because a fire isn’t able to provide a clean burn of the wood. A struggling fire due to wet wood can lead to increased production of smoke, creosote and other harmful products.

In order to burn wet wood a fire must first burn off the excess moisture within he wood before it can be properly combusted.

During this time a fire is using more energy to burn off the moisture and providing an incomplete burn of the wood.

Incomplete combustion of wood can lead to increased smoke, creosote and other harmful particulates being produced by your fires.

These emissions can contribute to poor local air quality.

It’s therefore always recommended to only burn properly seasoned or kiln dried firewood, where the moisture content of the wood is at an acceptable level that will lead to a clean burn of the wood with significantly reduced harmful emissions.

Can Seasoned Or Kiln Dried Firewood Get Wet?

Seasoned firewood is wood that has been air dried outside, while kiln dried firewood is wood that has been artificially dried in a kiln.

The aim of both seasoning and kiln drying wood is to bring the moisture levels down until the wood is useable as firewood. Properly seasoned or kiln dried will therefore already be low in moisture content.

Seasoned or kiln dried firewood can get wet without causing long lasting issues. If either seasoned or kiln dried firewood gets wet then they can still be used in your fires as long as they have had time to dry out again.

If seasoned or kiln dried firewood has got wet because of rain then look to stack it in a dry location outside for up to a week for the excess moisture to dry off. Rain will only typically affect the outers layers of the wood.

If firewood has been submerged in water then it may take a much longer time for the wood to dry out. Keep an eye on any firewood that has been submerged as it dries by using a moisture meter to check how the drying process is progressing.

Further Reading

How To Season Your Own Firewood

How To Stack Firewood For Seasoning

What A Cord Of Firewood Is

A Guide To Seasoned Firewood

A Guide To Kiln Dried Firewood

Why Firewood Pops and Crackles

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