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Re-Drying Wood from Outdoor Storage
Question
Forum Responses
From the original questioner: Thanks. I am sure some of it has been rained on, as there are no sides to the shed she stored it in - only a metal roof - and winter storms bring strong winds with them. She sent me a photo and it shows the top of the lumber covered with blown in leaves. It was always stickered, so would that have helped? From contributor R: It will need to be dried again to bring the moisture down. We have limited indoor storage and whenever we have extra flooring from a job, it gets stored in our hoop house - side and top cover, but no heat - in New England. We have our own Nyle L200 dehumidification kiln. Test it with a moisture meter to find out for sure. From contributor J: I wonder if storing it inside for a length of time will bring the moisture back down? The wood will not regain all the moisture lost during the initial drying. The question is how much moisture did it gain? A moisture meter would tell you this instantly. From Professor Gene Wengert, forum technical advisor: The outside conditions are about 16% EMC, so the wood, especially the ends, will be close to 16% MC after a long storage. It is critical to get it back to 7% MC before using it so it will not shrink, warp, open glue joints in use. If the outside was less than 6 months, warm storage at 30% RH should bring it down. Otherwise, a kiln. When checking the MC, use a MC meter with insulated needles. Take a reading at every 1/8" depth as you drive the needles in. We woud hope that the higher MC readings will just be the shell and that the core is at 7% MC still. If so, then warm room drying. If the core is above 7% MC, then kiln drying is most prudent and safe. In either case, insects (powderpost beetles) can be in the wood (it may take up to 2 years for the eggs to hatch so sometimes the wood looks great, but the insects are there and will show up after something is made). So kiln drying to get the wood's internal temperature to130 F would be the best.
From the original questioner: Thank you, Gene. I never thought about powderpost beetles getting into it, so end of story. I will go to the kiln. Thanks for your help! What a great group of people. From Professor Gene Wengert, forum technical advisor: There may be beetles in the wood already, so keep this wood separate from any of your own wood (and other people's too) until after it is dried. It would be best to avoid having the KD wood in the same location that the original wood was in or in contact with undried 4x4s, etc. From contributor T: It is better to have it kiln dried again. You can apply some lacquer or wax on both ends of wood to prevent cracking. Then the lumber will not warp or crack due to the loss of moisture. In case of twist, you can also tie several together with each one side by side during kiln drying. Space among each bundle is required for hot-gas recycle. If the wood was not ever dried before, it would take more time and be more difficult to have it kiln dried, because of the molecular water. From contributor I: What do you mean by "molecular water"? It's seemed to me that kiln dried wood is much easier to redry - do you understand why? From Professor Gene Wengert, forum technical advisor: In the USA and Canada, and much of the world, we do not call it molecular water, but rather free water. Would you like to add information to this article? Interested in writing or submitting an article? Have a question about this article? Have you reviewed the related Knowledge Base areas below? 
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