I dont know why they have to lie about it. At $5/8ft board you’d think I paid for the full 1.5. Edit: I mixed up nominal with actual.

  • Captain Aggravated
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    8 months ago

    Construction lumber, especially pressure treated lumber, is sold so wet I don’t think it really matters. I’ve actually never tried to calculate wood movement for construction lumber because who the fuck cares? But for furniture lumber which is dried to between 6 and 14% moisture, there is a formula:

    width of the board in inches x percentage of moisture change * expansion coefficient for a particular species.

    Yellow pine (extremely common construction lumber) has an expansion coefficient of .00263. A 2x4 (actual dimension 1.5" by 3.5") that undergoes a 4% moisture content change will grow/shrink 3.54.00263 = 0.03682 inches, or just over 1/32". That’s in width; it’ll vary by less than half that in thickness. Wood basically doesn’t move along the grain; the board won’t get appreciably longer or shorter.