Wooden door frames near the toilet area can get damaged by water easily. Sometimes we do encounter door frame that are rotten near the bottom due to water damage by water over a long period of time when cleaning the floors.
Recently we were engaged to do a partial patch up work for a rotten door frame without painting. We start by removing the rotten portion which is at the bottom part of the frame with care as the rear of the door frame has tiles by the side.
After which a new portion of the frame is inserted and nailed by machine into the wall. Last but not least the gaps are covered by putty. Finally a paint is coated over (not in pictures) to cover the wood.