Wood Window Damage
Wood windows works fine located in
bathrooms as long as they're not located inside of the shower. Wood and
water don't seem to mix too well and over time, there's a very good
chance that the window can suffer from water damage.
Even if these windows are prepared and painted properly, the amount of moisture inside of the bathroom, if it isn't ventilated properly can cause the wood to swell and this would make the window hard to open or close.
You can repair the damaged wood, but I would recommend replacing the wood window with a vinyl one. Vinyl windows are made from plastic-based materials and will last a long time if exposed to water or moisture.
In the picture above, there is a vinyl window with a wood window sill. And you guessed it, it's located inside of the shower. Now the damage will be a little different here, the window sill provides plenty of room for soaps, shampoos and hair conditioners to be stored until discarded.
As the wood window sill gets wet from using the shower, the moisture that is exposed will evaporate quicker than the moisture underneath the shampoo containers. The moisture underneath the containers can stay there for days, during the right conditions.
The longer the moisture stays on the wood window sill, and more susceptible it will be too water damage. The problem isn't the wood window sill by itself, water can leak behind the window sill and eventually damage the wall framing.