Lots of people will throw out numbers for what they consider good moisture levels, but in the end stable moisture is reliant on your local absolute humidity levels, absolute humidity being how much water is in a certain volume of air rather than how much water is in that air compared to how much it can hold at that temperature (which is relative humidity)
The stable moisture level will be significantly lower in Arizona than Indiana.
Here in humid Indiana, we will generally consider things to stabilize around 12 to 15% moisture content. I have heard that in some places that level can be as low as 6%.
Now from here on lets be careful lest we turn this into a green framing v. seasoned framing debate... (I am on the green side myself) But suffice it to say moisture level is only a concern to some. There are those who use carefully dried timbers in their frames, and there are those who put it all together green. If you are letting your own timbers air dry, then you need a moisture meter. If you are doing with green or Kiln Dried wood, then you don't really need one, unless you are operating your own kiln of course.
