Tubs and Showers in a Stack Log Home:
The design of your bathroom in a stack log home has some special considerations. In your typical five feet by eight feet bathroom, the tub/shower fixture usually goes against the outside wall. There are other ways of arranging the layout, but this is the one that will have the most impact on the logs themselves.
In a stick frame home this is not a big issue. Waterproof the wall with the proper materials. If there is a window in the wall, make sure it is tight and caulked. Maintaining the integrity of the seal will prevent water from getting into the wood behind the finish, which is your main concern. A stack log wall is solid, the individual logs are round and the wall settles. Where your frame walls meet the log walls there will be slots to tuck the drywall into for a nice clean line. These factors do make keeping the water out a challenge.
One of the best ways of eliminating the possibility of water problems is to reorganize the layout and move the tub/shower away from the log wall. This will allow you to show off the logs and it will reduce your maintenance. If you cannot move the tub then you must prevent the water from getting at the logs. The minimum would be a top quality sealer for log homes and maintain the finish on a regular basis. Another simple preventative measure would be to have a shower curtain that fully encloses the tub, as this would keep all the water away from the log walls. A claw foot tub would be an excellent choice for this option.
A better and more long term solution would be to frame a wall in front of the log wall. This will allow you to waterproof it and protect the log wall. The top of the furred out wall does not need to go to the ceiling, but you will want to be mindful of the settling of the logs if you do. If you have a window in the log wall, special consideration will have to be made to account for the movement of that window due to settling.