My question is regarding rot within the walls. Has anyone ever come across this, and if so, what can be done about it? Can it be costly to fix? Is there any way at all to tell before the wall is opened up if this is going to be a problem? The house is about 30 years old, but the room that the slider is going in was added on after the house was built. The roof is in excellent shape, but there does appear to be a couple of small water stains on the ceiling.

The contractor we are working with said he's only run into this a couple of times in his 15+ year career, and the last time was in a house that was over 100 years old. I just need some reassurance that this project isn't going to end up costing us twice as much as we budgeted for, or more!

Any suggestions or advice?

Thanks!