The two decrees that gave Haussmann’s Paris its uniform streets: the first let the city take whole plots for new streets, made a building permit compulsory and required façades to be kept clean; the second tied the height of every house to the width of its street and bounded its roof by a 45° line.
Paris had regulated the height of houses since the royal declaration of 1783–84, which fixed about 17.5 m (54 feet) as the maximum on streets 30 feet wide or more. The decree of 26 March 1852, issued in the first months of the Second Empire, gave the prefect the powers that Haussmann would use from 1853: expropriation of whole parcels for new streets, the obligation to submit plans before building, the connection of new houses to the sewers and the periodic cleaning of their fronts.
The decree of 27 July 1859 revised the height rule for the new boulevards. On streets of 20 m and more the façade could rise to 20 m to the cornice; on narrower streets the older limits applied. Above the cornice the roof had to stay within a line sloping at 45°, which produced the characteristic Parisian roof: a steep slope of zinc or slate pierced by dormers, with a flatter top. Combined with the alignments imposed on new streets and the model elevations required in the conditions of sale on some of them, the rules made the continuous, level-corniced street wall that is still the image of Paris.
The book, part by part
I Decree of 26 March 1852
Expropriation, building permits, sewers, the cleaning of façades.
Rules: One street, one front
II Decree of 27 July 1859
Height to the cornice tied to street width; the 45° roof.