In figuring the percentage of the lot that a building will cover, deduct the area of the court, sides and yard space. The tenement house law in New York City will not permit a building built on an interior lot to cover more than 70 per cent of the area of the lot. On a corner lot there is no restriction placed on the percentage of area that may be covered, but the yard of the corner building must be 10 feet wide for a distance of 50 feet back from the street, and thereafter 2 feet wider, if the building be five stories high; and one foot more for each additional story that may be added, so that for a twelve-story building on a corner lot 100x100, the yard would be 10 feet in width for 50 feet of the depth, and 19 feet in width for the remaining 50 feet. The widths of courts and shafts are all dictated by the tenement house law. It is therefore possible, when all these laws are observed, only to cover about 80 per cent of a corner plot, unless it has an extreme amount of frontage in comparison to its depth.