The challenge: The homeowners, a couple with a young son, had a large master bedroom with a walk-in closet, but no bathroom in their vintage Minneapolis home. They wanted to create a private owners' suite where they could relax and unwind at the end of the day. Space wasn't an issue. A previous renovation had combined two small bedrooms to create a large room with a sitting area — plenty of space to fit a new bathroom. But figuring out how to weave new plumbing down through the old house without disrupting other walls would be challenging.

The team: Architect Mindy Sloo of MM Studio, Minneapolis; designers Victoria Sass and Carrie Valentine of Prospect Refuge Studio, Minneapolis; contractor Mike North Construction, Orono.

Hide and seek: Sloo noticed something as she observed the exterior of the home. "There was a window on the north side of the house, where the bedroom is, that wasn't visible from the inside. It had been Sheetrocked over at some point." That happy discovery meant that there was another window to add to the suite of rooms without having to alter the 100-year old exterior. And the window was in a perfect spot on which to center the doorways from the bedroom to the closet, and closet to the bath — creating a nice focal point and the bonus of natural light.

Period details: To make the space feel in keeping with the age and character of the home, Sloo included details that would make it seem like they had always been there, including cased openings on the doorways and trim on the windows, ceiling and baseboards that matched the rest of the house. New cabinetry in the closet and bathroom also were designed to complement a century-old home.

Check-in time: "The owners wanted a timeless design that felt cohesive with the rest of the house and quietly luxurious, like a five-star hotel," said Valentine. "They're well traveled people who have stayed in a lot of nice hotels, and they thought, 'Why not have this at home for ourselves?' " The design team chose to avoid anything trendy like Moroccan or subway tile in the bathroom, and instead chose natural marble in a variety of shapes and sizes. In the bedroom, they went with a tonal white palette with lots of subtly textured fabrics in wool, linen and cotton. Wall-to-wall carpet was removed in favor of the original hardwood floors, plus a large, custom-made wool rug that would feel comfy underfoot.

Not fit for a king: In order to make room for a new bathroom, the owners had to sacrifice the sitting area and, more dramatically, go from a king-size bed to a queen to accommodate its placement in the windowed alcove. "The clients had to decide if they were ready for a cozier sleeping arrangement. They had originally started out with a queen bed, so this was a return to their first years together," said Valentine.

Warming up: The bedroom alcove was cold in the winter, largely due to four drafty windows. They were replaced with more energy-efficient versions, along with heavy pinch-pleat drapes and roman shades (made by the homeowner's mother), in creamy shades of white, to add privacy and create a luxurious and insulating cocoon for sleeping. A bulky radiator was replaced with a slimmer baseboard version — an essential swap to ensure that the bed and two small nightstands would fit in the space.

Finishing touches: "As important as maintaining a dialogue with the rest of the house was, we also wanted to incorporate a little freshness and modernity to the space," said design principal Sass. This was achieved through furnishings and finishing touches, such as alabaster lamps, leather nightstands and a contemporary wood ceiling fan in the bedroom, and a soaking tub, modern side table and oval glass knobs in the bath — subtle details that make the space feel current, but not too contemporary. "We want these rooms to look as relevant 20 years from now as they do today."

Laurie Junker is a Minneapolis-based freelance writer.