Tucked Under a Stairway
This option makes use of an area that's frequently underutilized. For privacy's sake,
it works best in homes with an enclosed foyer that opens into adjacent entertaining spaces. The two biggest obstacles are providing ample headroom (I recommend a minimum height of
5 feet above the toilet; check your local codes
for height requirements) and ventilation (an exhaust vent will need to be run to the exterior). Place the sink or vanity on the tallest wall so hand washers won't bump their heads.