Most of the 2x4's I have for an exterior wall I'm constructing are slightly bowed. Also, the boards i'm using for the top and bottom plates are slightly twisted. Can they be a little off or do they need to be close to perfect? Will the boards straighten out when nailed together or should I get new lumber? Thanks
Theory on crowns facing out:
The crown should face the inactive side of the wall. If you are building an exterior wall, the crowns should face toward the outside...which would be the inactive side...since inside you may be hanging cabinets(inside in this case is the active side of the wall).
http://www.youtube.com/watch?v=6lSJ4Mwr-Uw
Theory on crowns facing in from the Journal of Light Construction:
I've framed several houses with 2-story balloon-framed exterior walls. On one such house, three 16' tall walls formed the living room. I selected studs with
very little crown, and crowned them out, but when I was later installing the ceiling joists over these walls, I noticed the studs had all developed much greater crowns than they had when the wall was built. I wondered why.
On another occasion, a fellow framer stopped by my job, and while he was talking to me, he flipped over the 2x12's on the top of the pile, noticing they were starting to cup. This would let the other side dry out, of course.
The proverbial light bulb turned on! The 2x's were exposed to the air/sun on three sides, so those faces dried out and pulled together. The bottom face remained moist, due to its contact with the board under it. I reasoned that the same thing was happening with the studs. The edge of the stud attached to the sheathing was not drying as much as the rest of the stud. As the exposed parts of the stud dried out, those wood fibers pulled together, resulting in a "cup" along its length, thereby
increasing its crown! Atleast that was my theory.
I tested my idea on the next house which had a 19' tall balloon wall at the entry. Crowns in, not out. When I got on top to set the joists, that wall's studs were practically perfect!
I now frame all my exterior walls this way, still checking the studs' crowns after the wall has been up for awhile, and most all of them straighten out, or atleast end up with less crowns. The balloon walls still end up nice and straight!
Tom
