Basically this is a simple section dealing mainly with wood sub floors and their respective supportive framing members. Very often the damage occurs under wet areas like that found in bathrooms or kitchens.
That is not to say that water damage is limited to only wood floors. Water or chemical damage can occur to other areas as well. When dealing with stone or ceramic tile, any damage to a structure that will adversely affect the tile or its intended performance needs to be repaired. This work ideally should be completed prior to the installation of the tile work and its supportive structures.
The following photographs were obtained in a 1950's residential shower. There are additional details of this job in the section on Replace Leaking Shower Pan. The detail concerning the reason the shower pan failed is also found in the Replace Leaking Shower Pan section. Suffice to say that the shower pan meant to be waterproof for many years had failed long ago.
Nevertheless the tile and mortar were removed exposing a badly damaged and deteriorated wood sub floor.
The wood sub floor had originally been constructed of 1"X8" Douglas fir boards laid diagonally to the 2"X6" flooring joists that had been laid 16" on center.
It was a blessing to find that the 2"X6" joists were still intact and were salvageable as framing/supportive members. The 1"X8" boards were mostly rotten. At least the ones that were closest to the shower dam.
If the wood can be easily removed by a simple scraping action of a claw hammer or compresses easily load, it needs to be replaced.
As seen in the photographs, the damaged wood is removed handily with a reciprocating saw, circular saw, jig saw, hand saw, or any type of device used. Whatever tool is chosen try not to damage adjacent surfaces or structures. Also, be sure to wear the appropriate safety devices.
Once the damaged wood is removed, new wood is placed and securely fastened. In this case the new wood of choice is ¾ exterior plywood as it was very convenient to have a joint in the middle where the new shower drain is to be placed.