Adding a washer and dryer to an apartment in NYC requires permits from the Department of Buildings (DOB), approval from the building management and the Co-Op or Condo Board, and work by licensed and insured contractors. You will also need an architect to produce plans and file an application with the DOB. Some minor alterations and ordinary repairs, such as plumbing fixture replacement, do not need a permit, but still require a licensed plumber. However, gas dryers require an exhaust vent to the outside of the building, which may involve more complex work. Therefore, it is advisable to consult with a professional engineer, registered architect, or the DOB’s borough directors before installing a washer and dryer in your apartment.