Moisture Meter for logs - report

I recently ran an enquiry here about using a moisture meter for checking the moisture level in wood for a wood burning stove.
There wasn't much help offered - in fact there was a degree of flack about wasting effort and money.
Well, I think that is worth feeding back what I am finding.
The first thing is this quote from the website of a wood burning stove manufacturer :-
"Wood
Most types burn well provided they are properly seasoned with a moisture content below 20%. NOTE.- It is bad practice to burn recently felled timber or wood that is wet. The heat output will be poor and it will cause excessive tar deposits to form in the chimney. "
I was questioned in the original thread over my statement that the flue had blocked possibly because of damp wood being burnt. I think that statement is now justified - the caveat is the 'possibly' but this is clearly stating that the tar level will go up if the wood isn't dry enough.
The quote also gives a baseline figure for acceptable moisture content.
I bought a cheap two pin digital read-out moisture meter off Ebay. I used it to check the moisture level of a stack of well seasoned (5 years old most of it) pile of logs stored in an open, roofed, log shed and found a consistent level of 18% at the surface of the wood. I then cut up several of these logs and found that the moisture level was 18% throughout.
I then investigated the beech that I have recently been logging - this is off a tree that died 15 months, fell 11 months ago and was cut up in May. It's moisture level is 25% currently and again is consistent throughout each log.
For a tenner this has given me valuable information and reassurance.
I don't apologise for now thinking two fingers to the naysayers.
Rob
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robgraham wrote:

That's a neat idea Rob. I hadn't thought of using a moisture meter to check logs. It also confirms that even long-dead trees need to have a drying period after being felled and cut up.
Peter Scott
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On Fri, 30 Nov 2007 04:28:57 -0800 (PST), robgraham

Can it do loaves? Cake? What moisture level should a good cake have?
--
http://www.freedeliveryuk.co.uk

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robgraham wrote:

My advice on sweeping the chimney/flue still stands...

If you re-read one of my posts, this what I said:
"If the tree has died, then after around 15 months, the only moisture in there is going to be from the rain, if it was put under cover after it was felled then it should be dry enough to burn surely?"
Was the beech put under cover when it was felled?
With regard to "I don't apologise for now thinking two fingers to the naysayers" then that's your prerogative - but my grandfather used to burn logs as a main source of heat and he *never* had a problem (he didn't use a moisture meter either), but he did sweep the old flue four times a year.
Brian G
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"he did sweep the old flue four times a year." - that as you will appreciate, Brian, just allows me to come in with the point that he had obviously found it necessary to sweep it that frequently because of the damp wood he was burning !! :>)
There did seem to be a general attitude of negativity amongst the replies to my original posting and considering the low investment cost I was surprised that no one had gone down this route out of curiosity if nothing else.
My attitude was that at a tenner this was a no brainer - OK I may be a bit of gadget freak in that I've also just bought for the same sort of price an infra red thermometer to let me check the radiator settings and the wood burner outlet temperature. Interestingly the latter has lead me to find, and double check, that the pipestat was hopelessly out of calibration.
My original quest was to find out an opinion on cheap moisture meters - the opinion was that the idea was nonsense. I bought one regardless, have found it an excellent little tool and have reported thus here.
Rob
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In message

Well done you
that's what I say
--
geoff

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Rob,
I have a large pile of wood and a log burner being installed. Have searched on ebay for 'moisture meter' but there are about 100 of different designs. What model was yours?
Davy

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I had a wood burning stove and also a very damp house some years ago. I found that using my multimeter on the ohms range and sticking the two probes into the wall or log got a resistance read out which was reduced as the moisture increased. I presume all that a moisture meter measures is electrical resisitance.
Once you've tried it out on a few examples you quickly get to know what are acceptable figures and what is damp.
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I'll reply to Davy here too. The model I got was the 2 pin one coming in from Hong Kong for 99p +10 postage - only took 4 or 5 days to get here. Seemed the cheapest option and works nicely - how long for is another matter of course !.
As far as being able to judge the moisture level of wood by hand, I'm not too sure about that as I've been burning wood for 25 years and I would have said that the beech I recently logged was dry enough, but the meter is showing it at 25%. Another log had me surprised this morning - I got some old agricultural oak that had been used as shed legs. It seem really heavy in contrast to some dry beech which made me suspect it's moisture level, only to find that it was only 12%.
OK the meter cold be seen as a toy, or a bit of geekism, but it is supplying me with some usable information, and it doesn't take any time just to reassure oneself that the wood is good.
Rob
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robgraham wrote:

Surface moisture goes up and down like a yo-yo. You really need to split the log to get a true indication of the MC
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.
Rob Density of wood has a huge variation. Oak can be nearly twice as dense as pine See http://www.simetric.co.uk/si_wood.htm Chris
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Dear Rob As you say, at 10 it was a no-brainer and will provide you with a reasonably accurate method of assessing how effective your drying process is. Wood will naturally equilibrate to 18% if it is kept under shelter and ventilated. (in stick of some sort) As long as you establish a system of storage and drying that is consistent (size of log etc) once you have determined how long it takes (plus a factor for the weather) you need only use your meter as an occasional check. Good luck Chris
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With softwood 17% (aka "shipping dry") is considered immune from fungal attack, and is the level you expect in joinery stuff from a timber merchant. It may then air dry down to 15% in summer but not, apparently, any further

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I've kept bees since my 20's and one of the early things I got from the books that came with the job lot of bee keeping stuff I got, was the fact that bees "dry" the honey from the 80% moisture the nectar comes in at - they actually digest it and sick it back up into the cells - to 18% moisture at which point any bacteria or yeast cells are killed by osmosis, and hence the honey keeps ad infinitum in the wax sealed cell.
I never made the link with the storage of other organic materials until many years later I met a grain storage man - and yes it's 18% there too, and logically of course that applies to wood, etc. as well.
I know that one of the problems that my cabinet-maker brother faces is the worse than desert like dryness in many modern houses where anything in pure wood shrinks and cracks horribly. I believe his reckoning is that many are in 10 to 12% area.
Rob
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... and do they use cheap moisture meters ?
--
geoff

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robgraham wrote:

No, I've never really made that connection either.

Tell me about it! In the softwood area "furniture grade" is normally kiln dried from green to "10-12%" in one process at source but, for economic reasons, that option is only feasible for big manufacturers.
Taking the standard 17% stuff and having a merchant in UK dry it further ("secondary kilning") is the only real option for the cabinet maker, but the results are never as good. Softwood kilning is a complicated business and best left to the Scandinavians (but not the Russians!)
IIRC US hardwoods are suppled at 10-12% for the kitchen trade but, again, how many cabinet makers can handle (physically or financially) a container load? Maybe the market has opened out a bit since I was involved.
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Rob,
I have a large pile of wood and a log burner being installed. Have searched on ebay for 'moisture meter' but there are about 100 of different designs. What model was yours?
Davy

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