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Thread: Drying Pressure Treated Lumber

  1. #1

    Drying Pressure Treated Lumber

    I'm working on a project that involves gluing up 4 pieces of 2x6 PT lumber to make a 2' x 2' board. I want to make sure the wood is reasonably dry before gluing. Right now the lumber is stacked on edge in my basement with a dehumidifier running and I have a box fan moving air over it. Is there anything else I can do to speed up the drying process without all the usual cupping, twisting and warping that PT typically goes through when losing moisture?

  2. #2
    Join Date
    Sep 2013
    Location
    Wayland, MA
    Posts
    1,479
    Start with KDAT lumber (kiln dried after treatment)? Real lumber yards will have it, the box stores don't.

  3. #3
    I would recommend that you stack and sticker those boards with substantial weight on them so that they will stay flat and straight. Drying them as you have stated will likely lead to disappointment.

    I would also recommend that you get a moisture meter so you know when the are truly dry. It will take months or more for the interior to dry out.

  4. #4
    Join Date
    Sep 2006
    Location
    Deep South
    Posts
    3,810
    I special ordered #1 KDAT pressure treated lumber at a high premium to replace the railing and posts on a large front porch. It seemed to me like the definition of "kiln dried" was wiping the wood off with a towel. It took 3 months of air drying to get the lumber to 12% in a hot garage before I used it.

    Quote Originally Posted by roger wiegand View Post
    Start with KDAT lumber (kiln dried after treatment)? Real lumber yards will have it, the box stores don't.

  5. #5
    Join Date
    Sep 2016
    Location
    Modesto, CA, USA
    Posts
    2,879
    Since we have no idea where you live can you give us a hint about the climate there. Is it a desert or a swamp? Is it summer or winter now for you?
    Higher humidity and lower temperatures will slow the drying process.
    I put PT out in the sun in summer and return about 80% to the store because they warp too much. It has only been over 100 a few days this summer so it takes a little longer this season.
    Bill D
    Last edited by Bill Dufour; 07-18-2019 at 11:35 AM.

  6. #6
    Join Date
    Feb 2014
    Location
    Lake Gaston, Henrico, NC
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    3,954
    I keep some in a storage building that has tin on the South side, and roof. It gets really hot in there in the Summer. I just leave it standing on end, and let it do what moving it wants to. After a year, or two, I know what will move, and what won't. The pieces that move get short parts cut out of them, but there is still some waste.

  7. #7
    I buy a couple of extras in each size I need and sticker stack any pressure treated lumber I use. If you get the semi dry boards off the top of the stack at the box store, they'll never straighten out. I would much rather have something further down in the stack, still wet and heavy, and by stickering when I get home I have a better chance of controlling the degrade as much as possible.

  8. #8
    Join Date
    Mar 2003
    Location
    San Francisco, CA
    Posts
    8,672
    If what you need is a pressure-treated flat plate, you might consider starting with pressure-treated plywood, and laminate enough layers to get the thickness you want. I understand that the mill treats the laminates first, and then glues them into plywood. They have to dry the laminates before the glue-up to get the glue to take.

  9. #9
    Join Date
    Feb 2014
    Location
    Lake Gaston, Henrico, NC
    Posts
    3,954
    One thing that helps is to only pick boards with straight grain. Any time we're buying framing lumber, I glance at the treated stacks of 2x8's, and larger. If there are any clear boards laying on top of a new stack, chances are good that there will be more near those. I'll buy any good ones, and add them to the rest. I really don't get much loss by doing this.

    I don't bother to look at stacks that are less than half of a whole bundle. Those have already been picked through.

    Any board with grain that changes direction going down the board has a chance that approaches zero of staying straight.

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