Installing wood floors in a bathroom does not seem like an ideal solution because most people foresee the wood cracking and splitting, growing mold, and requiring too much care and attention. There are a number of alternatives to reduce the impact of moisture and its related problems on a wood floor.
Type of Wood
Choose an engineered, pre-finished wood. The wood should be well laminated so as to sustain the high moisture levels inevitably found in any bathroom
Once you purchase the wood, store it in the bathroom for a few days in order to allow it to acclimate to the high moisture levels.
Allow for Expansion
Bear in mind that wood will expand. Allow for some expansion gaps while installing it. You can then use floor trim to cover such gaps.
You will need to cut the wood so as to fit everything neatly. It is best to use a jigsaw for such a task.
Once you have installed the wood, vacuum to remove dust particles. Then patch problem areas with wood putty. Apply a coat of sealant in order to add extra moisture protection.