In the 1840s, a farmhouse was erected in Bridgehampton, New York, a quiet agricultural community on the South Fork of Long Island. The builders relocated an old one-room schoolhouse from the main street of the village and turned it into a wing of the house, a common practice in the 19th century — why waste perfectly good wood?The mudroom\u2019s ceiling light is by Schoolhouse Electric & Supply Co., the 19th-century mirrors were found in Antwerp, the pine floors are from Heritage Wide Plank Flooring, and the door is painted in Coach Green by Fine Paints of Europe. The house continued to grow over the decades, with additions in the 1870s and 1900s, until it became something of an architectural jumble, with an ill-suited Italianate cornice and porch columns. Still, it was a lovable jumble. Five years ago, a couple with three young daughters stumbled across a listing for the house on 1stdibs. The Manhattan residents already owned a weekend house in neighboring Sagaponack.Awnings shade the back of the house.\u201cWe\u2019d always been enamored with the idea of finding an idyllic farmhouse,\u201d says the wife. \u201cBut we didn\u2019t plan on moving. My husband said, \u2018Over my dead body are we buying another house.\u2019 Then we drove to see it the next day, and within 24 hours, we had put in an offer.\u201d It was clear, however, that their new purchase needed to be gently coaxed into the 21st century. Through mutual friends, the couple became acquainted with the family who had, until recently, owned the house for three generations. In a bathroom, the ceiling lights are by Remains Lighting, the walls are painted in Benjamin Moore\u2019s Stonington Gray and the window frame is painted in Genteel Gray by Pratt & Lambert; the wooden ship artwork was found in Europe.\u201cIt hadn\u2019t really changed much,\u201d says the wife. \u201cSame layouts, same floors. The only change they had made since their grandmother\u2019s day was to add bathrooms. Back then, they would use chamber pots.\u201d The couple soon realized that they didn\u2019t have a clear sense of how to make the house function for their family. Enter Steven Gambrel. The husband and wife, who both work in the hedge-fund industry, met Gambrel when he did a project for one of her colleagues. The interior designer, who has worked on dozens of homes in the Hamptons, has also owned six cottages in nearby Sag Harbor. He embraced the farmhouse\u2019s mix of architectural styles. The dining room\u2019s Julian Chichester chairs are covered in Lulu DK and Rose Tarlow Melrose House fabrics, the 18th-century pendant light is French, the curtains are of a fabric by Eskayel and the trim is painted in Aegean Teal by Benjamin Moore.\u201cIt\u2019s a quirky house, and I didn\u2019t want to lose that,\u201d he says. \u201cThe 18th-century schoolhouse wing is an important part of the history of the area, and I wanted to maintain its spirit.\u201d Nonetheless, the house had to be largely reconstructed from the foundation up. Gambrel enlisted Historical Concepts, an architecture firm based in New York and Atlanta that builds and restores houses while respecting a project\u2019s local vernacular, from materials to colors. The kitchen\u2019s marble sink has fittings by Sonoma Forge, the cabinetry is painted in Benjamin Moore\u2019s Hearthstone, and a collection of 1930s Bea Evan paintings found in Europe are in new frames by Bark Frameworks. In the end, says Gambrel, \u201cevery single thing was replaced except the interior staircase and railing. But it looks like the same building on the outside.\u201d In fact, it looks immeasurably better. The inappropriate Italianate details have been jettisoned. In the master bedroom, the bed is upholstered in an Arabel Fabrics linen and dressed in Schweitzer Linen bedding with a Serena & Lily quilt, the sofa is covered in a Mark Alexander fabric, and the chair and ottoman are upholstered in a Lauren Hwang fabric; the side tables by Olivier Gagn\u00e8re are from Neotu, the chandelier is from the 1940s and the 1973 screen prints are by Robert Mangold. A new wing wraps around two sides of the building and encompasses the living room, master bedroom and a screened porch. The formerly choppy interior has been reconfigured to comfortably accommodate a contemporary family of five. The guest room in the poolhouse contains a John Himmel bed dressed in Schweitzer Linen bedding, a Swedish painted chest and a rug by Restoration Hardware; the matchstick Roman shades are custom. True to houses from this era, the rooms feel intimate, with low ceilings. \u201cIt\u2019s not a grand home,\u201d says Gambrel. \u201cIt\u2019s rambling and charming.\u201d At the beginning of the endeavor, Gambrel walked the clients through his own Sag Harbor residence. \u201cMy husband and I fell in love with its cozy elegance,\u201d the wife says. \u201cWe wanted that vibe, and Steven gave it to us.\u201dIn the living room of a weekend home in Bridgehampton, New York, designed by Steven Gambrel, the custom sofa is upholstered in a Mark Alexander fabric, the same Arabel Fabrics linen is used for both the curtains and the armchair, the Thebes-style caned stools are vintage, the cocktail table is by Dos Gallos and the abaca rug is by Stark; the ceiling is painted in Super White by Benjamin Moore, with beams in Armory by Pratt & Lambert. A custom sofa in the living room is upholstered in a de Le Cuona fabric, the side table is by Henredon, the chest is a 19th-century ship\u2019s cabinet and the French still life is from the 1930s.For their living room, Gambrel chose a palette of pale neutrals. \u201cIt\u2019s old Hamptons,\u201d he says, \u201cSand and biscuit and oyster and driftwood, dry and not shiny. The room is meant to look like it\u2019s always been there.\u201d The family room\u2019s custom furnishings include a sofa upholstered in a Lee Jofa fabric, a tufted sofa in a Chapas Textiles weave, a leather ottoman and a pair of armchairs covered in a Kravet linen blend; the 1950s cerused-oak side table and 19th-century copper lantern are French, the curtains are of a Home Couture fabric and the wallpaper is by Phillip Jeffries.A lofty family room now occupies the schoolhouse wing, which has a similar color scheme but is accented in bursts of green and blue that complement the garden outside the window. Bohemian patterns give the room a younger, hipper feel. The laundry room\u2019s washing machine is by LG, the seagrass hamper is from Crate & Barrel and the marble wall tile is by Walker Zanger.A pair of run-down buildings in a corner of the yard posed a challenge. \u201cOne was a potting shed with a huge tree growing out of the middle,\u201d the wife says. \u201cThe other was a garage that was so rotten with mold, I wouldn\u2019t let my kids near it.\u201d On the covered porch, the dining table and benches are of New Zealand teak, the rattan sofa by Bielecky Brothers has cushions in a Perennials fabric, and the pendant lights are from Circa Antiques; the walls are painted in White, the ceiling in Silver Gray, and the window frames and doors in Black, all by Fine Paints of Europe. Gambrel, working with Historical Concepts, transformed the structures into an entertainment space and a guesthouse outfitted with a bedroom, dining table, bar, and fireplace. Beside the pool, the awning is made of salvaged corrugated-and-wired glass, and the custom outdoor furniture is topped with cushions covered in a Perennials fabric; the pool surround and patio are of Kota stone and the topiaries are boxwood; the garden design is by Marders.The family installed a pool, as well as an open-air glass pergola for lounging that was inspired by a greenhouse-style dining pavilion the wife had admired at Stockholm\u2019s Ilse Crawford\u2013designed Ett Hem hotel. The hardest part about working with Gambrel, the wife says, is the fact that the home is now complete. \u201cWhen Steven leaves your life, you feel like a little bit of creativity slips through your fingers. I\u2019m dying to find another project to work on with him, because he brings so much joy to the process.\u201dThis story was originally published in the June 2017 issue of ELLE DECOR.