Seasoning firewood

[Mark A]

Hi chaps,

Earlier this year I started to cut and split firewood myself, with the intention of becoming less reliant on bought logs or scavenged timber and pallets.

Back in September a couple of oaks blew down and blocked the lane. My neighbour, the farmer who owns the surrounding woodland, let me help myself to the remaining logs. The oak was cut, split and stacked in my woodshed, with the expectation that it wouldn't be ready for burning until the following year at the very earliest.

Today I split and probed a few bits of oak with my new moisture meter and was very surprised to see a reading of 21%, as it's only been four months. The thing is, all the other telltale signs of seasonedness I've read about, like end grain cracks, peeling bark and a hollow sound when clunked together haven't arisen yet. The wood still looks, feels and sounds a bit green.

Can a moisture meter be relied on to determine the readiness of firewood, or would it be best to wait for the other signs to materialise?

Cheers,
Mark

 

[Fitzroy]

I find the best way to tell with oak is to burn a piece, if it hisses due to escaping moisture then it’s not ready yet.

F.

 

[porker]

I treat moisture meters as a relative measure. I don't think the cheap ones at least, are that accurate and I tend now to use my experience to tell if it is dry enough but are good to reference against a known good bit of wood. As you say the telltale signs and weight are the best indicator. For oak I would expect it to take longer than 4 months but it depends if it was dead before it blew down or how healthy it was. I don't burn much oak as there is mostly beech where I live but I understand it takes longer than other hardwoods in general so I would have thought one season minimum.

 

[paulm]

I've recently ringed up and split for firewood a large diameter ( circa 14" ) fallen oak branch in my woods.

Looked like it had been down for a few decades given the moss growing on it and the punky sap wood.

Very pleasantly surprised to find that under the inch or so of wet, punky bark and sapwood, the heartwood, being oak, was perfectly sound, and the newly cut/split surfaces were all showing around twenty percent on the moisture meter so seasoned and ready to burn

I've stacked and stored most of it for the time being, but the bits I did use on the open fire at home over Xmas burned fine, lovely actually

The point being that if it has been standing deadwood, or downed, for some time, it is quite possible that it could be usable straight away, or at least quite quickly.

Had the same with a standing dead beech tree that I had to take down for safety, dry as a bone and good for the fire straight away.

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[Beau]

Hi chaps,


Today I split and probed a few bits of oak with my new moisture meter and was very surprised to see a reading of 21%, as it's only been four months. The thing is, all the other telltale signs of seasonedness I've read about, like end grain cracks, peeling bark and a hollow sound when clunked together haven't arisen yet. The wood still looks, feels and sounds a bit green.


Cheers,
Mark

The supposed telltale signs are very misleading but often quoted. Put a wet log in the sun for a few days and you get end grain cracks but it's not remotely dry. In fact, they will show more cracks when part dry due to tension between the shrunken dry wood on the outer edge and the wet middle then when they are fully dry and some of the stresses are relieved. Bark falling off is just a sign the wood has been left in the rain for some time but again no indication of how dry the wood is. Now the banging together is better once you get a feel for it but oak is never going to make a lightweight clunk when banged together being such a dense wood. Most meters should give you a good indication of how dry the wood is but having said all that it's surprisingly fresh oak has dried in such a short space of time as oak is a slow one to dry. As said above maybe it was standing dead in the first place? Try oven drying a sample and see if you get the same results and if you do happy burning.

 

[dzj]

Oak with an MC of 20% should be ~750 kg/m3.
A bit of math will tell you if your moisture meter is correct.

 

[Mark A]

Hi chaps,

I typed a reply on my phone last night but mustn't have pressed submit.

I have enough dry wood for the time being so I think I'll leave the logs cut last autumn for another few months at least, just to be on the safe side.

Had some good luck today. Mr. farmer pointed out several fallen trees I could have (in exchange for whiskey) so spent the afternoon collecting the easily accessible branches. Bought a winch tonight, so in the morning I'll be able to get to the trunks. Some branches had been buried under mounds of composted leaves for a long time, but the wood's perfect underneath.

Cheers,
Mark

 

[xy mosian]

My brother's supplier, in france, recommends 3 years for fresh cut and split Oak. At that stage apparently Oak has a higher thermal output, when burnt, than heating oil. It may all be a myth of course.
xy

 

[Beau]

My brother's supplier, in france, recommends 3 years for fresh cut and split Oak. At that stage apparently Oak has a higher thermal output, when burnt, than heating oil. It may all be a myth of course.
xy

When it's dry it's dry. There is no magic formula for this. Oak is slow but we happily dry oak in less than a year in the right environment.



This is my take on Seasoning Firewood

If your wanting to season logs the first thing to do is get it cut and split asap. The bark is fairly waterproof and inhibits drying so a fresh split face is better and end grain drys faster still. A cubic meter of fresh cut logs has approximately 150 liters of water in it so to dry them you need to maximise airflow around the logs to evaporate the water. We sell around 300 cubic meters of logs a year and the longer lengths are stacked in open sheds with slatted sides and a roof. The rows of logs have a gap between them again to maximise airflow. The front rows that get the sun dry in a matter of months with the right species. The smaller logs are loaded lose into crates and stored with covers but open sides to speed the drying. Pictures below

Most woods have a similar calorific value per dry kg but interestingly softwoods like larch and douglas fir are have slightly more energy by this standard but the differences are slight. In reality we buy wood by volume and this is where density of the species comes in with the likes of oak being near the best. Drying speed varies a lot from species to species. The likes of oak, chestnut and ash are slow to give up there moisture while sycamore, birch and beech are quick drying species. Now you will hear people rave about ash as firewood as it's often said you can burn it green. Dont burn anything green IMO as all woods are too wet when fresh cut unless standing dead. Ash is a funny one in that when fresh cut it will have less water in it than most species but it's slow to dry from here on. Beech is the exact opposite in that it is one of the wettest species when fresh cut to the point it can sink in water but it's fast to release it's water. My beech logs will get to 20% moisture content before the ash if all other things are equal.

As to how dry they should be I would say below 25% for sure and 20% is ideal and lower better still. All depends on your local climate as to what can be achieved. Wood being hydroscopic and given enough time it will find equilibrium with it's environment. If you live on the western hills 20% is about as low as you can get in the winter months but if you live in one of the dryer parts of the country 15% might be achievable. I would recommend a moisture meter to anyone who is serious about drying logs. It takes so much guess work out the process. To test a logs split it down the middle or cut it half and test there. Yes meters are not 100% accurate but close enough for logs IME

 

[xy mosian]

Thanks for that Beau.
In fairness the French supplier merely cuts his supply to length, normally 1m, sometimes 0.5m. Then it is stacked without special consideration to drying, other than a cover of some sort. He supplies cutomers who tend to use dog grates rather than dedicated stoves.
Thanks again, xy