Wainscots generally cover less than a third of a wall. In a bathroom, however, you have to factor in the height of the tub deck. A tile wainscot looks best when you have full tiles on the top row, as well as along the bottom. This means that you shouldn't cut the top or bottom rows to fit the standard wainscot height. Raise the height of the wainscot to accommodate full tiles.
Overall installation is the same for any type of wainscot, but in a bathroom you have to think about waterproofing. Waterproofing is an installation component and not a finish material. You can purchase waterproofing in several different formats, including paint-on and fabric systems that are self-adhering. Once the waterproofing is in place, you can install the wainscot on top of this layer.
Bathrooms are wet areas, and the bathtub is one of the wettest spots in the bathroom. As a result, there are limitations in terms of what kind of wainscot material you can use. While unfinished wood might sound charming, the reality is that water is going to stain and damage the wood after it is installed unless it is sealed. Another example is wallpaper. Tile, painted paneling or other water-resistant materials are better choices.
Similar to the way you have to worry about the height of the tub deck when you're choosing a finished height for your wainscot, you need to take into consideration the overall design of the room. For example, if you have a vanity backsplash with a pattern you want to carry around the room, you will have to adjust your wainscot accordingly.