When most people use under the stair for storage, you can try to have different idea. Use it for powder room. It doesn’t need large space. You only have to provide sink, bowl, towel holder, mirror, and some accessories if needed. Then, you will have functional under stair room.
Powder room may less priority. Due to this is a part of bathroom, so some people may ignore its role. However, this is an important place for women. They tend to repair their makeup anytime. Beautiful powder room will make women get their mood back. Magnificent powder room may seen through it mirror, sink, or pedestal.