Hello! Trying to have hardwood floor installed for Mom as a gift. Cannot afford to install in all rooms, only living room and hallway. After viewing home, contractor says gluing new floor is best, most economical option for different reasons: 10 because current parquet floor is very even and is good surface for glue, and 2) because new floor cannot be installed all over house, gluing wood keep the new floor at the approximate level of the flooring in the areas of the house that will not have new floor. The wood floor store says that nail installation and subfloor creation is the best option, because humidity in NYC could cause a glued floor to shift and cause gaps between wood pieces. However, the nailing/subfloor installation option would create different floor heights throughout the house. Even with reducers, new floors would cause significant height difference.Nailing option is obviously more expensive, would involve ripping up the current parquet, which is in excellent condition (but too thin for nails). Nail installation would also involve changing the closet doors as well as the entry door to the home. New wood flooring is 3 and 1/2inch mahogany, and is 3/4 inch thick. Current home foundation is 1/2 inch parquet glued to concrete. Home is 7th floor apartment in Manhattan, created in 2003. Building is 8 floors high. Wood store is ready to perform either glue or nail option, but I need to decide. Any suggestions as to which is best installation option - gluing or nailing? Want to please Mom. Please help!