Replacing Tar Paper from the Inside
I am remodelling my bathroom (first remodel for me).
The house is old, 1900, and one wall of this bathroom is an exterior wall of the house. Yesterday, we took the whole room down to the studs and discovered on that one exterior wall that the tar paper underlayment between the exterior siding and the studs was peeling off badly and mostly absent in large areas. My hunch is there was a bad leak from the bathroom immediately upstairs at some point in the history of this house.
So I've got two questions for the experts:
1) Is it imperative that I replace that rotten weather proofing?
2) If yes, is it possible to replace or otherwise repair it from inside the house, while I have that wall open?
I have pictures I can send to anyone who really wants to diagnose this further.
Thanks, Nick Merz