Troubleshooting Cracks in Kiln-Dried Live Oak
Experts attribute a cracking problem in 8/4 Live Oak slabs to drying the wood too fast at too low humidity. August 26, 2008
Question
I live on the southeast coast and had a live oak cut into thick slabs 8/4. I picked them up at the kiln and they are full of cracks, mostly in the heartwood, some all the way through the slab. Can anyone tell me what happened? Is it a problem with the wood or the kiln? I paid to have this dried and I'm not going to be able to use the wood for much of anything. Any information would be helpful.
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Forum Responses
(Sawing and Drying Forum)
From contributor D:
It looks to me that they tried to dry it too quick. With the 8 quarter they should have taken an extra bit of time. I have found the heat tries to drive the water out too quickly and can turn to steam instead and do just what I see in your picture.
From Gene Wengert, forum technical advisor:
Live oak takes special care to dry without these cracks. Whoever dried this wood, especially high MC’s, did it wrong.
From contributor H:
I once bought a T/L of 8/4 oak just like that (at a very good price). It seems the kiln operator, as Dr. Wengert stated, did it wrong. Too hot, too fast and too long! I was able to use it but not until it surfaced down to 1 1/4. I did have some tension problems in a few of the units.
From the original questioner:
I'm really disappointed. I got this log from a campground here that is being developed into condos and have lots of people interested in buying what I would have made out of these 10 slabs. I paid to have them cut, paid to have it dried, and now it's junk. We cut it 2 1/2" thick and had to plane it down to 1 3/4" because of cupping and still I have all these cracks, on all the boards and some go all the way through. If I get another opportunity to get more logs how should it be dried?
From contributor D:
As for your lumber, definitely go back to the guy that dried it and demand satisfaction. The argument can be made that he ruined what was perfectly good material, and should replace the dollar value. That is a regional species, and anyone in the region in the business of drying wood should know what and how to do it right. If you want to use the lumber for anything other than firewood, then I suggest filling the open pores with epoxy and sandust, and sanding so the epoxy is only in the pores. It should look pretty good.
From Gene Wengert, forum technical advisor:
The shed must have some air flow, but not much. The RH must be high initially.
I also agree that the drying person owes you some money.
From contributor R:
Did you air dry it at all before sending it to the kiln, or was it green from the sawmill?
From the original questioner:
Thank you all for your advice. It was green, we brought the log to him and were there when it was slabbed, then left it with him to dry. He's had it for about a year and I'm not sure if he air dried it first or just put it in the kiln.
From contributor S:
8/4 will take less than two weeks if you could find a good vacuum kiln. And it should go in green with absolutely no air drying. But it's too late for that. All you can do is fill the cracks but they are at the rays and filled won't look that much different to the untrained eye.
