[pizzafeelsright]

I have remodeled a dozen houses of and haven't hit anything of importance. How:

Study the building code to determine with >95% accuracy what is behind the wall based upon surrounding fixtures.

[Quarrel]

You're going to be in trouble once you get to 20 houses :)

[mrgoldenbrown]

How do you know the building code from 100+ years ago? And whether they actually followed it back then?

[pizzafeelsright]

100 years ago there wasn't really code, or electricity or extensive plumbing and everything is pretty obvious.

As for following - after the 50's everything was, in theory, built to code with exceptions.

Worse case really is hitting a water pipe.