You need to speak to an architect to see if it is possible for you to do such a thing. There are laws, safety codes and zoning restrictions you have to be concerned about. You can find an architect and get together to go over it. You will need the address of the property and the survey from when you purchased your home.
Whatever you do, make sure you do it in a legal fashion. This means you have to submit the plans to the city, get them approved and once the work is done you need to have the city come and re-inspect to make sure everything was done properly and up to code. After that you will be given a new certificate of occupancy attesting to the legality of your alterations.
If you do not do it the right way you can be subject to violations, fines and it will also interfere and create problems when you go to sell the house anytime in the future. So call an architect and do it the right way. If I can be of further assistance, please let me know. Good luck!
Mitchell S. Feldman
Associate Broker/ Director of Sales
Madison Estates & Properties, Inc.
Office: (718) 645-1665/ Cell: (917) 805-0783