A Haussmann apartment house
The Parisian immeuble de rapport under the 1859 decree: ashlar front, shops with awnings, continuous balconies on the second and fifth floors, a cornice at 20 m on a boulevard and a slate mansard with dormers inside the 45° line.
The rules it illustrates
Height from the width of the street. Tie the height of every house front to the width of its street: on streets 20 m wide or more the cornice may stand at 20 m, on narrower streets lower; above the cornice the roof must stay inside a line rising at 45°.