If the washroom and bathroom are handmade without using ready-made products, it will be quite unique.
In PAC houses, we often use a half-unit bathtub with Japanese Sawara wood boards for the walls and ceiling, but daily maintenance of the boards is easy.
All you have to do is wash off the dirt from the shampoo and soap with the shower water after the bath.
No water drops will drip from the ceiling.
Since it is a solid wood, it will change its color to a lighter color over time.
It may be partially moldy, but it is a characteristic of solid wood that you can easily replace only that part.