First principles: sight down every piece of timber before cutting and installing. For framing you can live with cupping across the timber and bowing in either direction up to a point. Wind (twist) is another matter - any pieces exhibiting wind need to.be put to one side and used for stuff like sole plates and noggins where they can either be fixed down to flatten them, or where the length is short enough for the wind to be insignificant over the length. Accept the fact that you may get one or two pieces in a delivery which is unusable. If you have to install timber that is bowed or twisted a straight edge such as a 4ft level will give an indication how far out the timber is (once the whole frame is assembled) and minor discrepancies can often be corrected by the judicious use of sharp jack plane. Twist you should try to evenout between sole plate and header to minimize the amount of correction you need to do.. After it won't ever be seen. If a noggin wont fit it may be a case of cutting one end or the other a few degrees off 90° in order to get a decent fix (see pics 1, 3 and 5)
TBH i always order 5 to 10% over quantity in order to be able to weed out the crap. Timber is a natural material and is never going to be perfect even from the best merchants
Foxhole - we use treated htinbers for framing in places like cellars, or wherever there is damp. I have to admit thst it generally isn't brilliant stuff to use
