LumberJocks

Keeping kiln dried lumber DRY.

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Blog entry by James Lango posted 1986 days ago 2551 reads 0 times favorited 8 comments Add to Favorites Watch

I live in north east OHIO. The 12×20 outdoor shed also serves as a my dehumidification kiln. Kiln itself is 6×12, insulated, heated and sectioned off from the main storage area. It is a gambrel type shed/barn. I can dry smaller loads of harwood in my kiln. After the batch is dry enough for use, the next load has to go in. How long can I store the DRY load above in the sheds attic?(Gambrel roof design allows me to stand up in the middle, I can store alot of wood up there) The dried wood is in the 6-9%MC range. Is it possible for the dry load to re-absorb moisture?
Think about this; You can buy dried hardwood from Lowes, HomeD, lumber yards etc… They have the lumber sitting in isles, on store shelves etc. Have you ever though about how long those particular boards have been sitting on the store shelves?
When you walk into those huge stores, the relative humidity is pretty much equal to the outdoor enviroment. “equalibrium”
So DOES wood re-absord?
Thinking further- Store bought lumber has to make the journey from kiln to wholesaler, to retailer. Sometimes traveling by train, truck etc. And again spends some time sitting on shelves before being bought.

So will the wood go from say 7% to 10-15% in a matter of days, weeks, months, or never?
Many times when i buy wood for a project, it sits for a few weeks before use. And I know my “garage shop” is not less than 30%humidity.

Little confusing when you think about the science behind it. Thank you JAMES- Ohio

-- Longovette@Roadrunner.com



8 comments so far

View childress's profile

childress

841 posts in 2140 days


#1 posted 1986 days ago

YES!!! wood will reabsorb. It’s called reaching EMC – Equalibrium Moisture Content. That is why wood moves with the seasons. It’s losing moisture in the winter (cooler air holds less moisture) and absorbs moisture in the summer.

Your shops absolute humidity (amount of water vapor in grains per cubic foot) determines relative humidity depending on the tempurature. If your shop has 50% RH @ 70deg. your wood will have aprox 9% MC when it reaches EMC.

Get the book “Understanging Wood” by Bruce Hoadley. He goes into detail on this stuff (and other stuff as well)

-- Childress Woodworks

View dennis mitchell's profile

dennis mitchell

3994 posts in 2913 days


#2 posted 1986 days ago

Try not to think about it.

View BarryW's profile

BarryW

1015 posts in 2505 days


#3 posted 1986 days ago

A moisture meter is a must…if you don’t already have one. A good one….I like Lignomat…

-- /\/\/\ BarryW /\/\/\ Stay so busy you don't have time to die.

View dougdeg's profile

dougdeg

107 posts in 2369 days


#4 posted 1986 days ago

How did you build your dehumidification kiln, what type of system do you have was it hard to build, how long to dry a load of lumber

-- Doug Cedar Log Furniture, www.cedar-stuff.com

View HalDougherty's profile

HalDougherty

1820 posts in 1835 days


#5 posted 1064 days ago

James,

I mill my own lumber, dry it and store it to make custom laminated rifle stocks. I air dry it till it’s below 20 percent moisture. My shop is in a 2 story farmhouse and after air drying, I stack it in my attic. The house has a tin roof and in the summer it’s at least 130 degrees in the daytime and cools off at night. Plus the heat pump is removing moisture all the time. In the summer fresh cut lumber will air dry in 30 days and 30 more days in the attic be down to between 8 & 12 percent moisture. In the winter it’s about 120 days stacked & stickered outside and then 120 days inside. I cut sample pieces from the center of a board or two and weigh them. Then dry them in the oven till they stop losing weight and calculate the moisture content. They will gain moisture in a very short time to get back to from 8 to 12 percent. After the wood is dry, I never take it back outside till it’s finished and it’s being shipped to a customer.

-- Hal, Tennessee http://www.first285.com

View mmccoy1951's profile

mmccoy1951

27 posts in 1268 days


#6 posted 1064 days ago

Wood can be too dry just as easy as it can be too wet.I have seen flooring buck up because it was not allowed to equalize.Wood here in Western NC seems to equalize at about 12%.I had some poplar flooring stored in my barn for over a year and it gave no problems after we put it down.This is just me but I like to let wood rest for at least one week after it has finished drying.I also run only the fans for 24 hours after the kiln cycle is done.I don’t know if this is a good practice or not but it seems to work for me. Mike www.sawmillwnc.com

-- Mike

View pintodeluxe's profile

pintodeluxe

3270 posts in 1412 days


#7 posted 438 days ago

I just took some readings from red oak that was kiln dried, and stored in my unheated (but insulated) garage for over a year. It is still at 6-8% moisture content, so it hasn’t changed much. If I put it in the barn, the M.C. may well climb, however in the garage it is fine.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View Echofive's profile

Echofive

90 posts in 1851 days


#8 posted 42 days ago

So if wood reabsorbs, which I understand it does, what moisture content should wood (maple in my case) be before sealing it? Doesn’t that lock moisture out?

New England has had a lot of rain this year. I have some maple I want to use for a project and it keeps cupping. As it dries, it flattens back out, but it’s obvious when there’s more moisture in the air. I was thinking about putting it in one of those big vacuum bags with some rice to help dry it out.

Thoughts?

-- Chip, Massachusetts

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