This article is part of our Design special section about new interpretations of antique design styles.

One might describe Andrew Trotter’s passion for Puglia, in southern Italy, as a slow burn. The British-born, Barcelona-based designer first visited the region, which forms the heel of Italy’s geographic boot, about a decade ago. His close friend Carlo Lanzini planned to create a boutique hotel that would cater to the growing number of travelers lured by Puglia’s charming medieval villages, its sun-bleached landscape dotted with ancient olive groves and its nearly 500 miles of coastline, featuring picturesque coves with limestone cliffs and lovely sand beaches.

Mr. Lanzini enlisted his help in finding and renovating a masseria, the name of the traditional whitewashed farmhouses found across the Pugliese countryside. “We went twice, both times in the winter, and I didn’t actually like it very much,” said Mr. Trotter. “It’s a place that’s grown on me rather than an immediate love.”

At that time Mr. Trotter, who is 51, had recently left a career in fashion, launched a short-lived Barcelona design shop and co-founded Openhouse, a boutique and gallery that evolved into a semiannual interiors and lifestyle magazine, with his friend Mari Luz Vidal, a photographer. Having studied interior design and spent a year at the London firm of Anouska Hempel in the early ’90s, it was a return to his roots.

When Mr. Lanzini ultimately decided to construct a new masseria-inspired building for his hotel venture, near the town of Ostuni, Mr. Trotter put himself forward to oversee its design. After some convincing, he got the gig, and the resulting six-guestroom Masseria Moroseta “very quickly became a little bit famous,” as Mr. Trotter put it, leading to other commissions designing and renovating vacation homes in Puglia, including for Mr. Lanzini as well as new clients who admired Mr. Trotter’s minimalist yet warm aesthetic.

While Studio Andrew Trotter soon had projects in locations around the world, Mr. Trotter and his domestic partner — the firm’s business manager, Marcelo Martinez, 31, who is Spanish — continued to travel to Puglia regularly. They decided to look for a residence in the region that could serve as their base and as an income-generating rental property when they weren’t using it. Their search led them to the southern Pugliese town of Soleto, in the heart of the Salento peninsula, where a centuries-old house, tucked into a cobbled alley, caught their attention. “The town is very sleepy, and it’s something I love about the real south of Puglia, which is very untouristic. In the smaller villages you feel like you’re in a movie, like ‘Cinema Paradiso,’” Mr. Trotter said, adding, “We’re the youngest people in Soleto.”

Even though an offer had already been made on the house, the couple convinced the agent to let them have a look. Behind the front wall and arched stone gate with large wooden doors, an open-air courtyard served as the entry to the two-story residence. Expanded in stages over time, the house incorporated two vaulted chapels, one estimated to be 400 years old, while parts of the upper floor were believed to have been added as recently as the 1920s.

The family that previously owned the property hadn’t used it in a long time, but many of their belongings remained, untouched. “There were clothes and furniture, artwork, photos of the family,” said Mr. Trotter. “But for about 20 years, nobody had come to the house. Nothing worked. There was no running water, no electricity. There was a hole in the back garden where the sewage went to.”

Not to mention, there was only one bathroom, the walls were wonky and decaying, and the only way to climb to the second floor was by an exterior staircase in the front courtyard. “That quirkiness is what gives charm to the house,” Mr. Martinez said. Features like a 15-foot vaulted ground-floor ceiling gave the interior a character and mood that a mere glimpse at plans and snapshots did not reveal.

Also, the house was exactly the size they wanted, and it had a garden with enough space for a small pool. When the other offer fell through, they “just went for it,” Mr. Trotter said. (He declined to divulge how much the couple paid for the property.)

Mr. Trotter and Mr. Martinez, who discussed the project over Zoom from Barcelona, set about updating the house for contemporary living, making it comfortable and simply stylish, while retaining as many elements as possible to preserve the home’s distinctiveness and historic feeling. They dubbed it Casa Soleto.

For convenience and rentability, they added three upstairs baths so that each bedroom has its own, plus a powder room on the ground floor, all of which meant putting in extensive plumbing. New electrical systems were installed, though lighting was kept minimal. Many of the antique doors and existing floors — terrazzo tile or polished concrete — were preserved, and portions of the roof and walls were repaired.

On the ground floor, where the rustic walls were built with stones and earth up to three feet thick, Mr. Trotter and Mr. Martinez had to replace expanses of cement plaster added in the last century that were trapping moisture within. Throughout the house the walls have been refinished in subtly textured lime plasters or washes, in earthy tones from dusty beige to chocolaty brown to pale green. All were made by Domingue Architectural Finishes, one of a handful of firms the couple partnered with on the project.

The Scandinavian furniture company Frama provided an assortment of clean-lined wood tables, chairs and stools that complemented the mix of antiques and simple upholstered seating clad in solid, neutral linens. The Australian carpet maker Armadillo provided the jute rugs that are found in most rooms. (In exchange for their contributions, the companies can use Casa Soleto’s images and story in their marketing.)

Mr. Trotter and Mr. Martinez, who spoke by phone and over Zoom, kept some of the furniture left by the previous owners, including large wooden gun cases they repurposed as coffee tables, a few beds with distinctive headboards and, in the largest bedroom, a glass-front cabinet filled with old books accumulated by the doctor who once owned the house.

Resisting the urge to contemporize the kitchen, they instead worked with local craftsmen to restore the wood cabinets, replicating them for additional storage, and to create fronts for a built-in refrigerator and dishwasher. They installed an ILVE range that’s “quite old school,” said Mr. Martinez. “The goal was to make everything functional and up-to-date, but without trying to do something too contemporary or out of place.”

The couple used a fair amount of the artwork that had been left hanging on the walls, a mix of unattributed landscapes, still lifes and portraits. But they also commissioned new works from Eleanor Herbosch, an Antwerp-based artist who made three abstract paintings mixing ink with soil excavated from beneath the home and from the garden.

Ms. Herbosch’s works hang prominently in the atmospheric dining room, which occupies the later of the two chapels, at the front of the house, and a cozy lounge in the older chapel at the back, where they opted for a darker, moodier palette. “We wanted it to be a bit like a cave where you go and watch a film or just hang out, read a book,” Mr. Trotter said.

The garden has been completely reimagined, with a plunge pool and plantings selected with advice from the London landscape designer Luciano Giubbilei. A terrace connected to the largest bedroom overlooks the garden, while a smaller balcony off the front bedroom offers views of the nearby Gothic bell tower commissioned by the medieval nobleman Raimondo Orsini del Balzo. “It rings at 6:30 every morning, and on Sundays it’s not just a simple bong-bong-bong,” Mr. Trotter said. “It keeps going, every 20 minutes.”

Completed in July, the renovation of Casa Soleto took two years, and there’s nothing else like it in town. “The mayor and the priest came to see the house,” Mr. Trotter said. “Italians like to make everything new and perfect, and we’ve done it in a way that it still feels old, so I think they don’t get it.” But for him and Mr. Martinez, he added, “true luxury is not about being in super-polished perfection.”