New York-based Builtin Studio has helped a young family expand their Upper West Side apartment into the adjacent unit and create mid-century-influenced interiors that complement the historic details.After the family jumped at the chance to buy the neighbouring apartment to their current home, they tasked Builtin Studio with combining the two spaces and uniting them with the decor.The apartment's kitchen and dining area includes a chestnut island, olive green cabinetry and built-in seating around the table"What resulted is an elegant lesson in how to refresh a home for a growing family that is reflective of their needs and personality," said the studio.United after removing the dividing wall, the property measures 2,200 square feet (204 square metres) and now contains two beds, four baths, two offices and a den.In the light-filled living space, a navy sectional and pink occasional chair offer plenty of seatingThe entire interior was gutted to offer "a clean slate", allowing Builtin Studio to restore the traditional mouldings while rethinking the layout and the atmosphere of the spaces.An open floor plan connects the lounge to the kitchen and dining area, which includes a chestnut island and built-in seating around an oval table.Mid-century influences can be seen in the den's furniture and lightingKitchen cabinets are painted olive green, while the marble backsplash features golden flecks that match the range hood trim and Apparatus light fixture over the island.The mid-century influences are visible in the choice of dining chairs, as well as the furnishings in the den.Read: General Assembly creates "comforting and quiet palette" for Manhattan apartment"Given the complex's age, once a residency for Babe Ruth, Builtin played off of the apartment's historic character while modernising it," the studio said.In the primary bedroom, a neutral palette complements the rich wood used for the bed frame, side tables and millwork in the closet.Varied shades of blue can be found in the kid's bedroomThe kid's bedroom was designed to "strike a balance between maturity and playfulness", featuring various shades of blue across the ceiling, carpet, curtains and bedding.A moodier tone is set in the hallway bathroom, where earthy green plaster and brass scones create a sense of intimacy.A moodier tone is set in the hallway bathroom thanks to earthy green plaster and brass sconcesThe front office has high-gloss painted ceilings, steel doors and a built-in bookcase that again nods to the mid-century style.Other recently completed apartments on the Upper West Side include a pad by General Assembly that has a "comforting and quiet palette", and a residence by Messana O'Rorke that features striking marble bathrooms.The photography is by Trevor Parker.Project credits:Architecture and design: Studio director; Kyle Landau, designer; Connor TauntonConstruction: MKON ConstructionStyling: Mariana MarckiThe post Builtin Studio combines and renovates two Upper West Side apartments appeared first on Dezeen.