Lumber Storage After Kiln Drying

Advice on storing kiln-dried wood in the proper humidity conditions. November 14, 2009

I am new at kiln drying. I have a container that I use as a dryer. I have only dried a few loads of wood ranging from Oak to pine. I placed the wood in a building that is not heated or cooled. This building has a concrete floor that sweats sometimes. The lumber showed between 6 to 8 percent moisture after I took it out of the kiln. Now it shows as high as 12 with an average of 10. The moisture meter I am using is a Wagner that you just slide across the surface, no pins. I just want to know if that is acceptable to still sell as kiln dried lumber?

Forum Responses
(Sawing and Drying Forum)
From Gene Wengert, forum technical advisor:
Furniture, flooring and cabinets in a house will be at 6 to 7% MC, so a piece of wood, like oak, at 11% MC will dry substantially and shrink as it reaches its interior MC value. This can be a serious problem for many products. For construction softwoods, 12% MC is normal. Kiln-dried also means wood that is dried at over 130 degrees F to many people. This kills any insects, their eggs, fungi, etc. For softwoods for interior use, 150 or 160 degrees minimum is often expected as that will begin to set the resin.

Bottom line: for clarity and happy customers, you need to specify what sort of drying you provided and what MC level the wood is at before you attach the woods "kiln dried" to the lumber. Note that the meter you are using will respond more to the MC on the surface, so the MC may not be as high as you think. Borrow a meter with insulated needles or plane a piece of lumber and then measure the MC when the surface moisture is gone.

The final chapter in drying hardwood lumber talks about practical storage ideas. The storage facility that you are now using can be improved. Do you have room for another container that you can paint black or a dark color, keep outside, and then use free solar heating to provide the dryness you need?

From the original questioner:
Thank you for your response Gene. I may be able to add another container in the future. I wonder if a dehumidifier would help out any if I used one where I store the lumber? Also on the moisture meter I have, I read some more in the manual and it gave a list of several different species. Each species had different numbers. For example, if it was cherry bark oak and the meter read 10%, then this chart said it was really something like 7%, these numbers are just an example, I donít have the manual right in front of me now to give accurate numbers. The only thing about this chart is it gave several types of oak, red and white, and as far as my lumber goes, it might have been a load of lumber from 30 different species of red oak. When the lumber came out of the kiln I measured it and the meter read between 6 and 8, now keep in mind I only checked a hand full of boards that were in different places of the stacks. I just want to make sure I give someone a good quality product and when I tell someone something, it is what I say it is.

From Gene Wengert, forum technical advisor:

Somehow you need to store the lumber at about 35% RH. You can get this RH by heating the outside air or by dehumidifying it.

From contributor W:
You might want to paint the slab you're storing the material on. Maybe an epoxy paint with some sand or abrasive of some kind thrown in so it's not slick to walk on. Also, I've heard of guys wrapping a flat stacked pile of dry material in that stretchy plastic wrap used on pallet loads. That or just sheet plastic, tightly wrapped.