If it was the bathroom area was too narrow, so not possible to place the sink in it, Nothing unusual, really, to put the sink outside the bathroom. The important point to note is how and where the place, so the sink does not necessarily make the house so muddy.
The first thing to note is the sink function. If forced to put the sink outside, make sure you use it for activities that are not much use of water. Just brush your teeth, washing hands, or shave is still possible.
Where to place? Better, not far from the bathroom. So that continuity of its functions remain intact. After all weird as well, placing the sink in the family room or dining room? To keep the surrounding area remained dry, it’s worth putting the carpet of the material is thick and absorbs water. After all activities involving water, potentially result in water splashing around.
The next consideration in terms of design. Because stationed outside the bathroom, meaning very easily visible. Better choose a simple design, which does not simply place the sink bowl. Could complete it with tables, mirrors, and shelves, making the cantilever system, and many other creative ways.