Kiln Dried

[deema]

I would like to know if there is a standard for kiln dried, when stated for hardwood? I don't actually know what it means, my interpretation is that the wood should have a moisture content no more than say 12%, is there a British standard? And if so what's the definition?

Thanks

 

[Peter Sefton]

I am sure there is a British standard but I couldn't quote it. Aired dried timber should come down to around 18% depending on the season and weather conditions. The kiln dried % would depend on the specification of the drying yard or timber merchant. The American driers tend to bring there timber lower than ours, one thing to always bare in mind is that although a timber may have been dried down to say 10% if it has been stored outside in poor conditions it may have taken moisture back on and gone back to 18% again. Also most but not all timber merchants are full of BS :!:
Peter

 

[deema]

Thanks Peter,
I bought some oak, kiln dried and most if it was as expected at circa 12% moisture content! ok for most internal applications away from a heat source. But some if it was at 20%, useless for indoors without drying out! Felt rather miffed and that started me looking at what Kiln dried actually stood for before having a word with the merchant. I try to have a balanced view, and if it's my ignorance, well life is a one learning opportunity after another!

 

[KevM]

Deema, How are you establishing moisture content? Is it possible that you've just picked an anomalous spot for your measurement?

 

[Sgian Dubh]

I would like to know if there is a standard for kiln dried, when stated for hardwood? I don't actually know what it means, my interpretation is that the wood should have a moisture content no more than say 12%, is there a British standard? And if so what's the definition? Thanks

*North American kilned target is 7% MC ±~2% for furniture and internal joinery.
*The UK target for internal joinery and furniture grade is generally ±11% MC ±~1-2%, which I think applies to all of Europe, but I'm not 100% sure of that. I've heard there may be moves afoot within the EU for a lower target MC, but again I'm not sure if that's just a rumour or really on the cards.
*The target for kilned woods, mostly softwoods, aimed at the construction industry is approximately 20% MC.

As others have said, the MC can change significantly after kilning depending on how the dried pile of wood is packed and transported, and how and where the wood is stored.

In my experience it's very rare to find air dried wood below 20% MC in this country unless it's been air dried in some sort of open ended or open sided shed that encourages air throughput. More usually, especially if the wood has been dried stacked outside with no cover or just rudimentary cover, it will generally be closer 25% MC, especially towards the end of winter. Slainte.

Edit. I noticed I'd incorrectly placed the ± symbol without qualifying the accepted variation from the target MC for kiln dried wood, which I've now rectified. Sorry about the blooper.

 

[deema]

Hi Kevin M

I have a top spec Timbermaster moisture meter with a hammer probe. I've tested the ends (circa 3" in) and the middle. I've checked the calibration on the standard provided. A bit of a dumb moment in that I made a door frame out of the timber having checked a jamb and the piece to make the top rail, which were fine. Didn't check the wood for the cill or other jamb! These are now drying out with shakes appearing all over the place......grrrr!

The timber merchant stores under cover in an open ended shed. First time I've had an issue with MC.

 

[RogerS]

Out of curiosity I stuck my Wagner Moisture Meter on some air-dried ash (1" and 2") that I have had in my workshop for the last ten years. Readings were between 9.5% and 12%.

 

[Peter Sefton]

Yesterday I turned on my dehumidifier in the wood stockroom, the moisture content in there is generally between 9-11% but with the current weather it has crept up to the 13% mark - too high for my liking; should come back in line within the next week or so. Just worth keeping an eye on occasionally.
Cheers Peter