An important aspect of having a fire in anytype of fireplace, whether it’s an open fireplace or wood burning stove, is to ensure that the firewood is dry enough touse.
For wood to burn efficiently on a fire itneeds to have a low enough moisture content, so what moisture level shouldfirewood be?
Forfirewood to burn efficiently it should have a moisture content of 20% or lower.As the moisture content of firewood increases above 20% it gets progressivelyharder to burn effectively in a fire.
So how do you know whether firewood is dryenough, how can you measure moisture content in firewood, and can firewood betoo dry? We’ve explained moisture content for firewood in much more detail below.
The General Tools pin type moisture meter with LED bar graph display is perfect for detecting the water content in a variety of materials to help ensure the appropriate level of surface dryness before painting, sealing or treating. General Tools MMH800 Moisture Meter. It is the professionally best moisture meter for wood as it has both pin type and pins fewer modes to help you precisely measure moisture in the flat wood surface. The General Tools MMH800 has intelligent dual pad sensors to find the rapid areas of moisture in the wooden surface.
What MoistureLevel Should Firewood Be?
Many of the issues associated with poorlyburning fireplaces or stoves can be the result of burning wood that is too wet.These issues can include wood that isn’t:
- Catching alight properly
- Burning efficiently
- Generating much heat
- Burning without producing smoke
You may also notice that wet wood alsomakes hissing and spitting noises as the fire tries to burn off the excessmoisture. Wet wood is harder to burn because more energy is required by thefire to burn of the excess moisture before it can start to efficiently burn thewood.
Freshlycut wood can have a moisture content of anything over 20%, meaning that this ‘green’ wood is very high in moisturecontent and would struggle to burn on a fire.
The time of the year that the wood is cutcan also determine how high the moisture content of the wood is. Wood cut inthe winter months will typically have a lower moisture content than wood thatis cut in spring.
This is important because for wood to beuseful as firewood then it needs to have a moisturecontent of under 20% to burn efficiently.
To achieve this moisture content the woodneeds to be dried out, through aprocess known as seasoning.
The higher the moisture content of the woodwhen it’s cut, the longer it can take for it to dry out to recommended firewoodmoisture content levels. Cutting wood when it’s already low in moisture contentas possible can help to speed up the drying out process.
Seasoning wood can be a lengthy process. Certainhardwoods can take up to 2 years to dry out, while softwoods can typically takeup to 1 year.
Hardwoods such as Ash or Oak are from deciduous trees, which typically take longer to grow compared to softwoods such as Pine, from coniferous or ‘evergreen’ trees.
The slower growing process of hardwoods can mean that the wood grows more densely, meaning that the seasoning process can also take longer as a result.
Although the seasoning process for firewoodcan take a long time, almost no involvement is required once it has been setup.
To ensure that wood dries out in the mostefficient way, and to prevent it from rotting, the wood should be:
- Stacked on top of some sort ofimpermeable ground, such as concrete, to ensure that moisture from the grounddoesn’t seep up into the wood, and for any excess water to runoff into thenearby ground.
- Located under some sort ofcanopy, to help shelter the wood from the majority of the rainfall throughoutthe process.
- Open on one side to allow theweather to help dry out the wood, in particular the wind.
The wood also shouldn’t be directly coveredover by anything, such as sheet of tarpaulin, as this can trap the moisture andcause the wood to rot rather than dry out.
We season our own firewood to be used inour wood stove, and the picture below shows how we arrange the wood so that isdries out effectively.
You can read more about how we season our own wood here.
As the conventional seasoning process cantake many months or even years, a process known as kiln drying helps to vastly speed up the drying process offirewood. High moisture content wood is simply placed in an oven-like chamberwhere the excess moisture content is evaporated off.
You’ll typically find that bags of logs orkindling bought from your local store will have been kiln dried as stated onthe bags.
How Do You Know IfFirewood Is Dry Enough?
Dry firewood ready for burning looks a lotdifferent to wood that is freshly cut and high in moisture content.
The table below highlights the maindifferences between wet and dry wood
In summary, you can tell whether firewoodis dry enough if the wood is:
- Brown with no hints of green.
- May be splitting at the endswith cracks forming.
- The bark can be coming away oris easier to peel off.
- Can make a hollow sound whenpieces are hit together.
The images below show what you can expect adry piece of wood to look like.
Ultimately the best way to get an accuratereading as to whether firewood is dry enough is to use a moisture meter.
A moisture meter is a handheld device thatcan be used to accurately measure the moisture content of any wood by giving areading when pressed against it.
Moisture meters will typically have twometal pins that stick out the top (although some models of moisture meter canbe pinless), and will also have a digital screen on the front that will giveyou an accurate reading to typically one decimal place.
Here’s what our moisture meter looks like:
In many cases wood can be sold in bags as‘seasoned’ wood but the actual moisture content of the wood isn’t low enoughfor it to burn efficiently.
A study by the University of Tennessee (which can be found here) showed that a typically bag of ‘seasoned’ wood had moisture content values ranging from 50-90%, which is far too high to burn efficiently. The study concluded that low moisture content is key for firewood, and that the best approach is to buy and further season the firewood well before it’s needed.
We bought a bag of ‘kiln dried’ kindlingand logs from our local store and used our moisture meter to find out what theactual moisture content of the logs actually were.
The bag stated that the logs were ‘lessthan 20% moisture content’.
The moisture readings of a random selectionof the logs were found to be too low for our moisture meter to read, meaningthat the moisture content of these kiln dried logs was less than 6.8% (thelowest reading our moisture meter takes).
By checking these pieces of wood we’veensured that we’re not burning any wood that is too high in moisture content,which could have lead to problems being able to start the fire and keep itgoing.
How To MeasureMoisture Content In Firewood
In order to correctly measure moisturecontent in firewood you’ll need to have a moisturemeter.
A moisture meter is a simple-to-use toolthat gives you a very accurate reading of moisture content in firewood.
Tomeasure moisture content in firewood:
- Remove the end cap of the unit to reveal the pins, unless it’s apinless moisture meter.
- Turn on the moisture meter using the on/off button on the unit.
- Gently push the two pins at the end of the moisture approximately1mm into the piece of wood.
- The moisture meter will give a reading as to the moisture content ofthe wood.
How to measure moisture content in firewoodis explained in more detail below using our own moisture meter as an example.
If you have a pinless moisture meter thenyou’ll need to remove the part that covers the pins at the top end of the unit.
With the cover removed the pins are nowavailable to be used to read the moisture content. You’ll also need to turn themoisture meter on before using it.
To read the moisture content of any pieceof firewood, simply place the two pins against the wood. Both of the pins needto be touching the wood for the moisture meter to provide a reading.
The Environmental Protection Agency (EPA) recommends that:
- To ensure that you’re testingthe inside of the wood, moisture reading should be taken on any newly splitsides of wood.
- The prongs on the moisturemeter should run parallel with the grain when testing.
- 2-3 tests should be done indifferent locations to ascertain the overall moisture content of any piece ofwood.
Your moisture meter will then give areading on the digital display as to the exact moisture content of that pieceof wood.
The display on our particular model ofmoisture meter also lights up in either green, orange or red depending on themoisture content of the wood it’s reading.
In general, the lower the moisture contentthe better, and in the case of our moisture meter, it lights up green formoisture contents up to 15%, amber for up to 20% and red for any firewoodmoisture readings of over 20%.
As the seasoning process can take such along time, the EPA recommends that firewood with a moisture content of between 15% and 20% is most efficient forburning.
Ensuring that wood is dry enough to burn is essential for having a fire in your home that burns efficiently and effectively. Moisture meters are therefore an essential piece of kit for any type of fireplace or stove that burns wood.
If you don’t already have a moisture meter then we highly recommend looking into getting one. They’re an inexpensive purchase and will help to reduce a number of issues associated with burning wood that is too wet.
You can see our current favorite moisture meter over on Amazon here.
If you’re in the UK you can see our particular model of moisture meter over on Amazon here.
Can Firewood BeToo Dry?
For firewood to burn efficiently on a fireit needs to be as dry as possible, but can firewood be too dry or too wellseasoned?
Wood can be too dry to burn efficiently ona fire, but it’s not common to find a piece of wood that’s too in low moisturecontent that it would burn too fast on a fire.
Wood that is too dry can produce more smokethan wood with a slightly higher moisture content of between 15 and 20%, whichis regarded as the target moisture content for all firewood.
Wood won’t naturally dry out so much thatis becomes too dry, as the humidity will always mean that there’s moisturewithin the air and prevent firewood from drying out too much.
We’ve had a few pieces of wood in our homethat we haven’t got round to burning and that have been inside for over two years.
Wood Moisture Meter General Tools At Home Depot
Taking a reading of the moisture content ofthese logs showed that the moisture content was around 10%.
Wood Moisture Meter Review
Further Reading
How A Fireplace Works
Parts Of A Fireplace Explained
How A Wood Burning Stove Works
How To Use A Wood Burning Stove