The low inventory of luxury condos has owners looking for alternative ways to solve their space crunch. Increasingly, that means combining two smaller condos to make one large unit. In New York City, about 6% of condos and co-ops are now combinations, compared with just 1.5% four years ago, according to Jonathan Miller, president, Miller Samuel Real Estate Appraisers, which tracks the real-estate markets in New York and Miami.
