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Thread: How much will soft woods (ie, pine) typically expand and contract over, say, 20"?

  1. #16
    Join Date
    Apr 2015
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    New England area
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    588
    Face laminated lumber (think 2x4s or 2x6s glued face-to-face to make a benchtop) move through their thickness, and very little through the width as a glued top. This is why face laminations make great benchtops. Use your endcaps, screw the well board tight to the rabbet, and don't worry about it. The end caps and well board will move a little with the top as it expands and contracts through its thickness. Don't bother with glue on your endcaps (it's end grain gluing anyway) and of course no glue on the well board - just screws and not gigantic number 12s. 8s should be plenty, 6s even.
    Last edited by Charles Guest; 04-14-2022 at 5:10 PM.

  2. #17
    Join Date
    Dec 2007
    Location
    Valrico, FL
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    You are right, but most of us who build furniture consider wood movement the most important factor...not whether the wood is air dried or kiln dried.

  3. #18
    Join Date
    Apr 2017
    Location
    Michigan
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    2,758
    I have a tabletop glued up and waiting for the table to be finished. (taking my time on it) The top has moved 1/32" over 24" in 6 weeks. I'll have to fasten it in about 6 more weeks and have a total of 1/4" of play available. Just need to decide where in the play it's at then.

  4. #19
    Join Date
    Jan 2013
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    FINGER LAKES AREA , CENTRAL NEW YORK STATE
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    Quote Originally Posted by Luke Dupont View Post
    Yeah, I came across such charts but I have no idea how many percentage points the humidity here fluctuates indoors throughout the year, so I can't hope to calculate correctly.
    I was hoping for a general "rule of thumb that should work in most situations"

    Edit:
    Looking this up further, it seems there's a distinction between "Moisture Content" in percentage terms, of the wood, and "Relative Humidity" -- a distinction that I wasn't making as I first tried to calculate.
    https://www.thisiscarpentry.com/2010...wood-movement/
    Okay, but I still have no idea how to even measure moisture content, nor do I have a year to do so with a given piece of wood before I start building...
    Nor does Google seem to understand any of my conceived ways of wording the question "how much does furniture typically change in moisture content over the course of a year?"

    I'm just amazed that every article I come across just assumes you have all of this data and can therefore calculate everything and put a plan into action, lol
    This chart may help it lists values in equilibrium moisture for locations in the US and for cities around the world. file:///C:/Users/tflit/Downloads/WEBSITE_DOWNLOAD/FOR%20VIDEO%20EMC%20Equilibrium%20Moisture%20Conte nt%20of%20Wood%20in%20Outdoor%20Locations%20in%20t he%20United%20States%20and%20Worldwide.pdf
    The value of this chart and other interesting details can be see on this you tube video by Jonathan Katz-Moses https://www.youtube.com/watch?v=EOr06I9JoAU
    mike calabrese

  5. #20
    Join Date
    Aug 2019
    Location
    Pittsburgh, PA
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    827
    Quote Originally Posted by Luke Dupont View Post
    Yeah, I came across such charts but I have no idea how many percentage points the humidity here fluctuates indoors throughout the year, so I can't hope to calculate correctly.
    I was hoping for a general "rule of thumb that should work in most situations"

    Edit:
    Looking this up further, it seems there's a distinction between "Moisture Content" in percentage terms, of the wood, and "Relative Humidity" -- a distinction that I wasn't making as I first tried to calculate.
    https://www.thisiscarpentry.com/2010...wood-movement/
    Okay, but I still have no idea how to even measure moisture content, nor do I have a year to do so with a given piece of wood before I start building...
    Nor does Google seem to understand any of my conceived ways of wording the question "how much does furniture typically change in moisture content over the course of a year?"
    "Moisture Content" is a percentage value of the moisture content inside a piece of wood. You can buy meters for this.

    "Relative Humidity" is a measure of moisture content in the surrounding environment, in this case inside your house. Most household thermometers have a RH scale.

    You don't need an exact measurement of any of these values since they're varying constantly throughout the year. In a temperature controlled environment, furnace and A/C, the fluctuations of RH are not as wide as those outside. Your estimates need to use typical values for your house and the wood you're using. It'll give you an estimate of movement. Double it and design accordingly.

    Charts of movement of wet wood until it reaches equilibrium are not necessarily the same as the movement of wood already in equilibrium and just fluctuating due to ambient moisture changes.

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