# Kiln Dried VS Air Dried



## bbc557ci (Sep 20, 2012)

Hello everyone. I sometimes have the opportunity to pick up air dried rough cut hardwood lumber at decent prices. I read in another post here that if air dried, it should be about 1 year air dried per inch of thickness.

Now, I was told by a friend that, for inside trim and furniture building, the lumber must be kild dried. Of course I can see the advantages of kiln dried. But, my thought/question is, if I have some ash, poplar, oak, whatever, and the ambient humidity outside or inside the house is say 50%, won't the kiln dried lumer eventually take on about the same humidity level? I have a cherry table that I built about 20 years ago, and the top expands and contracts during changes in humidity. I live in central NY so inside the house the air is dryer in the winter due to the forced air heat. And in the summer it can get very humid.

Any thoughts and or guidance on the subject would be greatly appreciated.

Thanks - Bill


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## donwilwol (May 16, 2011)

All wood takes on the content from its surrounding. It's my opinion your friend is wrong.

I live just outside of Albany NY and I've been using air dried lumber forever. (yes I'm about that old) There are advantages to kiln drying (as you said you know) but air dried lumber can be used for anything kiln dried lumber can.

Now with that said, there are places where building code requires kiln dried lumber for certain applications, but I believe that's just framing, but its been a while, so don't quote me on that.

If you look through most of my projects, I'd bet 90% of them are from air dried lumber.


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## Dusty56 (Apr 20, 2008)

I'm in Western MA and haven't had any issues using air dried inside the house. 
Of course , after air drying , I allow the wood to acclimate to my shop (basement) for a few weeks to stabilize the MC before using it. I do the same with kiln dried…... Wood moves and we can't stop it.


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## bbc557ci (Sep 20, 2012)

Those are my thoughts as well. I had a small'ish construction biz for 25+ years and much if not most of what we did was finish carpentry related. I never used "air dried" on the jobs, as I needed to (and of course wanted to) guarantee out end product. And on my own home projects I didn't go with aire dried because I was not sure what the outcome would be. Might give it a go now though!!

Thanks for the input!!


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## Dusty56 (Apr 20, 2008)

Whether air or kiln dried , 8% MC is still 8% MC : ) JMHO


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## donwilwol (May 16, 2011)

I've got a moister meter you can get a Lowes or amazon. I think they are like $39. They go on sale once in a while for $29. Pick one up, they are handy whether its air dried or kiln dried.


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## Arminius (Dec 27, 2007)

For a lot of furniture applications, air-dried is better than kiln-dried. Kiln-dried is cheaper, because air-dried is indeed on the order of 1 year per inch of thickness, with all the costs involved. But air dried wood works better and is more consistent. At high temperatures, the lignin in the wood alters characteristics, and the wood becomes more brittle, often hardening at the exposed surfaces. The most obvious way to see this is try steam-bending kiln-dried wood versus air-dried, but even working with a chisel on two opposing samples of the same species will be pretty revealing.


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## bbc557ci (Sep 20, 2012)

I've got a moister meter you can get a Lowes or amazon. I think they are like $39. They go on sale once in a while for $29. Pick one up, they are handy whether its air dried or kiln dried.

I'll pick a MM up Don W….I should have one. Used to have one, but it got gone some how, several years ago.

Thanks again for the replies everyone it's appreciated.

Bill


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## MonteCristo (May 29, 2012)

I prefer air dried lumber because a kiln can screw up the wood and add a whole lot of built-in stress if the drying cycle is not right.

Also, some kilns mess with the lumber; eg some steam walnut to color the sapwood. Bad idea as you just get dull colored sapwood.

Don't take the 1"/year thing as gospel. It's just a very rough rule of thumb. Either get a good moisture meter or weigh a typical piece every week or whatever until it stops losing weight.


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## bondogaposis (Dec 18, 2011)

I prefer air dried lumber if it is truly dry. I think it finishes better and to me looks more "alive" than kiln dried. However I'm lucky that I live in an arid climate and lumber truly dries out out here over the course of a year or more. A moisture meter will be your friend here. Bring it inside during the winter for a while to let it adjust.


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## crank49 (Apr 7, 2010)

Kiln dried will only contain dead bugs or eggs where air dried may contain live bugs or eggs.
Otherwise, I like air dried.

And, some folks think a few worm holes just add character.


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## Dusty56 (Apr 20, 2008)

That's a good point , Michael : )


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## bbc557ci (Sep 20, 2012)

I agree crank49, few worm holes can and often does add character to wood. I recently picked up a few hundred BF of ash for trim work at my place, kiln dried, and there is one board that the critters definatly got to before it entered the kiln, which is fine with me!!

Thanks again for all the replies. This opens up new horizons for me )

btw…. just saw I spelled kiln "kild". Not quite sure how the heck I did that. Never could spell too well LOL.

Bill


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## Dusty56 (Apr 20, 2008)

You can go back and edit your title and post at any time , just not the comments here : )


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## SteviePete (May 10, 2009)

Rule of thumbs for drying wood completely miss the physical actions going on before and after its cut. Get Hoadleys book-be careful- he has so many facts you'll come off as a smarty pants. Best wood book I own.

As for me-I carve and like air dry or green wood. Plastic bags, sawdust, etc. Long winters give you a break. If you like what hoadley says you may be getting a meter or look for more rules of thumb that consider ambient RH, starting moisture in wood, wind speed, air temp and species.


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## Dal300 (Aug 4, 2011)

Our house leaks air.
My shop is a separate section from the house but served by the same HVAC.
Our house is old and compromised and even in the winter in Texas we seldom get to 15% RH in the house.

So that's what I air dry my wood to. Not just on the outside, I will cut a piece and see what it reads with the moisture meter on the inner parts.

As for bugs and other critters, I usually put the pieces that are under 24" in my oven @ 150-170°F for an hour.

Larger pieces require the heat box with some infrared lamps. We use to call it a bathroom, but it changed a bit over the decades.


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## RonInOhio (Jul 23, 2010)

So this thread has got me to thinking. Since wood usually (for furniture) should be dried to say
7-15% MC. Then, acclimated to the shop or ideally, similar to the humidity of the pieces final resting place.

Isn't it the uneven drying out that causes wood to warp ? As well, the taking on of moisture and release of 
moisture causes wood to expand and contract (or move).

So wood is more prone to warp and disfigure from drying out unequally, than it is from taking on moisture.Is it not why wood is dryed to such a low level of moisture ? Or am I over-thinking this. Maybe I am wrong in assuming wood doesn't warp by taking on moisture. I had some rafter ends warp on me that were exposed to 
outdoor spring air with no roof sheathing on them. 
So did those rafters warp because:
A. They were not dried enough ?
Bl They were partially exposed to the damp spring air and took on moisture unevenly. That is 
the top 2/3 of the rafter was covered with a tarp. Only the ends were exposed to the air.
C. Or being partially exposed, the ends exposed to the air were actually releasing moisture and 
the covered part of the rafter was not.

So the drying down to 7-15% MC its just to bring the wood to a stable MC so cutting and milling is easier and the piece will remain stable;or acclimate slowly as long as the surrounding humidity is not to high or low from the wood's MC.

No one's home should be anywhere near 7-15% moisture content or relative humidty. More like 25-55 % (roughly)humidity I would think in a home heated in the winter and cooled in the summer.

Guess I'm not sure of the relationship between ambient humidity and how that correlates to a woods MC. Other than to know the comfortable humidity range in a home is somewhere between 35 an 55 %. And wood tends not to warp or move much in this range. Unless the humidity changes from the low extreme to the high in a short period of time.


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## bbc557ci (Sep 20, 2012)

RonInOhio….sounds like we both dwell/think about cause and affect, for every action there is a reaction, etc. LOL

You mention moving wood when it's exposed to moisture or humidity…the top on the cherry table I made about 20 years ago moves with the seasons, even with several coats of ply on the top, and a couple of coats of poly on the bottom side of the table top. Common sense tells me the table is moving due to changes in humidity.

I've been in houses where in the winter, taped drywall seams have popped loose here and there. I have little doubt that dry air in the winter months contributes to that. In the house I moved out of a couple of years ago my primary heat source was a wood stove. Heat from the wood stove was really dry. I had trimmed the house out in ash. Corners at doors & windows were mitered. And I'd see in the winter where the 45s would open up a tad at the short sides. And in the summer when the wood stove was not in use, the joints would move back to perfect. That drove me nuts as I'm somewhat anol about my work (like many others here on LJ are, I'm sure). So, hence my original post. Oh. casings at doors and windows at this ouse will be cut at 90* and butted together, so I won't go nuts again )

My thoughts were/are that wood of most any kind will expand, contract, warp, move, whatever, due to changes in humidity. That's why it seemed to me kiln dried will eventually take on the MC of it's surroundings. So using air dried wood for the trim in the house I'm in now, and for other projects, should be ok as long as the wood used is "air dried" to the point that it has the same MC as its surroundings. Fortunately (for me), it seems allot of others here are thinking in that same direction.


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## Dusty56 (Apr 20, 2008)

It's ALIVE !!!


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