The Brooklyn architects nearly doubled the size and value of this little row house. Moreover, winning Landmarks approval set a precedent. With an additional floor at the rooftop and a two-story extension at the rear, this was the first big enlargement approved in Prospect Heights’ new historic district. The new top floor is all master suite with a private sun deck and a commanding view. The rear addition opens the living spaces to the backyard, while allowing for a large sunny kitchen. Finally, a new stair links new and old floors.