Renovations in Bed Stuy Landmark District

Im looking for some guidance. We just closed on a townhouse in Bed stuy in Landmark district and I would love to know What are landmark regulations are for renovations that show in the back exterior? Specifically we would like to add a deck and add a door off the back parlor level. We are only 4 house in from the corner and you can see the back of our house from the side street. Does anyone have experience with this or guidance to offer?