Quote:
Originally Posted by kccrow
A few cents...
2 things happen, generally... either it was wet and dried out or it was dry and acclimated (got wet). Air dried for a few months, you might be at 19-20% (<=19% meets the standard for making S-DRY or surfaced dry lumber that you'll see stamped at the box store) while kiln dried is usually 6-8% for hardwoods and 10-12% for softwoods. Either one, after time, will reach it's EMC which will be somewhere around 12% in the US, give or take depending on the relative humidity in the ambient air (might get up to 15-16%). Gaining moisture means swelling, twisting and cracking. Losing it can be the same thing basically, shinking twisting and cracking. The positive about kiln dried is that the lumber loses alot of it's elasticity so it usually won't bend and twist as badly as green or air dried. You're also going to notice alot more movement in larger pieces of wood, so your 4x4ss will move much more than your 2x4s. Tangential cuts will move more than endgrain cuts, etc.
If your lumber is treated, it would have been kiln dried before or after treatment with the latter being better. With kiln dried before treatment, you are drying the wood, then getting it wet, then letting it sit, then installing it where it will dry again and generally twist, cup, etc. If you get treated wood dried after treatment, it's far less likely to twist up on you. If lumber is treated after drying and you use it where one edge is exposed to sun and the other is exposed to ground or a wetter environment, expect that shit to twist.
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These are just vertical posts on the north end of the building, not really exposed to any sun. Purchased at HD. Is the big box store lumber typically dried before treatment?
Edit: Did some Googling and it sounds like I need to find some stamped KDAT, or buck up for real cedar even though that's not as good as it used to be. Or wrap the ****ing things with PVC sleeve.