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If you've got a basement, I'm assuming you're in the N GA mountains, correct?
Anyway, I'm in NE FL and air dry EMC here is 16% +/- depending on the wood species. IOW the lowest we can get air dry is 16%.
I don't work with slabs but I know they are notoriously bad about cupping. The thing is not so much the absolute MC but equal exposure both sides. I would sticker them with thick stickers like 2" to give plenty of air flow.
Personally I wouldn't be comfortable with 20%. I think the only way you're going to get there is a) move the slabs inside a climate controlled room or b) kiln dry. You can determine which option is best for you, but I do know there are heat driven as well as solar kiln plans out there and they aren't hard to build.
Some depends on how you're going to use them.
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(05-31-2024, 07:09 AM)plharrison Wrote: Thanks John. Not sure what the relative humidity is in my basement shop where they are currently. They are 1 1/2" thick. I should have mentioned that. I realized this was going to take a while which is fine. Not planning anything that needs to be done immediately. I do have an outdoor covered porch on the second level with a lot of room to leave them outdoors. Maybe I'll give that a try. A Georgia summer has very high humidity so that will be interesting.
I looked up the EMC for the cities listed for GA in the Forest Products Lab document on that topic.
It's hard to believe it's that low in Savannah in the Summer, but the FPL is a reputable outfit.
I don't know what the RH is your basement, but I would bet it's pretty high if you aren't running a dehumidifier. You can still get drying at 70% RH, even higher, if you move air across the wood. This is exactly how kilns work. You start out at high RH and then lower it as the wood dries. Indoors/outdoors, doesn't matter, but moving air over the wood is needed in any case to make it efficient. 6/4 walnut will air dry in my area in less than a year. FWIW, the EMC where I live is not much different from where you are, at least according to the FPL data.
John