This good-sized hotel, is in natural wood, normal, there should not be "treated". If you want to protect or decorate, color it, careful not to apply repellent by its composition, in particular stain, odor or other products too that will only push "clients" of the hotel! I bought a gift for my mother, it corresponded to his expectations, although it is a bit late in the season (late December) to provide shelter. Although, if there are still homeless ... The instructions are in English and German, so I translated it the need to install it in a sunny area, close to their food (roses and other draws -pucerons, grasses ...) quiet (so not next to the niche of the dog, even if he has fleas!) and protected from the wind. A country cottage 4 stars what! They say nothing concerning the protection of wood.