the real property so to be acquired for the purposes herein provided for shall be taken subject to such easement; provided, however, that nothing herein contained shall be so construed as to limit the power of the city of New York to acquire by purchase or by condemnation proceedings the entire plant or service of such individual or corporation, or to acquire such easement in such street in any other appropriate proceedings. The title in fee acquired by the city of New York to real property required for all purposes provided for in this title, except street and courtyard purposes, shall be a fee simple absolute.

PART IV

PLANNING THE PRIVATE FEATURES

CHAPTER I

THE PRINCIPLE OF BUILDING REGULATION AND ZONING

Building Regulation.-Building regulation may be roughly divided into three classes: Structural requirements, regulation of the bulk of buildings and other structures, and regulation of the uses for which they may be erected, or to which, when already in existence, they may be put in various parts of a locality. In connection with the regulation of the use of structures on land may conveniently be considered analogous uses of land without structures on it, as, for instance, for the conduct of the junk or lumber business or for the parking of taxicabs for immediate call. The expression "structural requirements" here used, means those other than of bulk.

Building regulations may be the same for all structures, or all of the same class, throughout the entire city or other administrative unit, or they may vary in the various parts of that unit. In the latter case they are called zone regulations. Use regulations, however, being intended to confine buildings employed for certain purposes to certain parts of a city, are necessarily zoning regulations.1

Retroactive Regulations.-Building regulations are not as a rule so drawn as to be retroactive.2 Existing buildings

'Regulations with regard to the construction of buildings of a certain class, throughout the city, for a given use, do not vary the character of the different sections of the city one from the other and are not in this connection classified as use, but as structural regulations.

'The zone regulations of Los Angeles are a notable exception; see p. 267.

and existing uses in them are rarely disturbed. At long intervals, as standards advance, minimum requirements for the occupancy of dwellings may be increased somewhat, and the employment of some of the worst apartments for living purposes forbidden until they have been altered to conform to the new regulations. For the most part, however, it is the bulk of future structures in different sections of the city (including additions to and alterations of present or future erections) and the uses to which existing structures shall be put and future structures devoted, that is regulated. The main purpose and effect of such regulations, therefore, is to prevent the beginning, aggravation and spread of undesirable conditions, not to cure them when already in existence.3

Structural Regulations.-Building operations in a modern city are almost invariably governed by regulations enacted for the purpose of guarding against flimsy construction, securing sanitation, etc. These regulations are usually contained in a building code, so called, and constitute the bulk of it. With these rules, in so far as their tendency is to secure these results, this inquiry cannot deal; for to do so would only lead too far afield and involve detailed discussion of matters technical in their nature and better treated in other connections. Often, however, structural provisions do affect materially the city plan, and sometimes are passed for the purpose. A favorite means in many communities of excluding the "three decker" (i. e., the three story tenement house, with an apartment to the floor, often covering an undue percentage of the lot) is to make the requirements for it so expensive that it cannot be built at a profit. The New York City tenement house law, passed in 1901, provided that all tenements over six stories in height should be fire proof, and later amendments have made the six story building proportionately more expensive than the five story structure.4 Chicago has for many years required all

* See, however, p. 200 with regard to non-conforming bulks and uses and their treatment.

'Originally Laws 1901, ch. 334, sec. II; now Tenement House Law, Laws 1909, ch. 99, sec. 15, renumbered by Laws 1913, ch. 551, sec. 2, to be sec. 14. See also same, sec. 24, Laws 1909, ch. 99, as amended, Laws 1913, ch. 551 and Laws 1919, ch. 648.

tenements over three stories to be of fire proof material.5 The result is that in Manhattan and other parts of the city, New York is prevailingly a city of six or five story residences, while in Chicago the three story type is the predominant one. At the time these fire proofing regulations were passed, a plain height limit prescribing such a maximum would have been difficult of enactment.

Bulk Regulations.-The principal purpose of bulk regulations is to guard against undue concentration. In form they are rules fixing maxima which structures shall not exceed. A measure of concentration in these communities is, on the whole, desirable. A city is the result of the division of labor, one of the consequences of which is the specialized use of land. Specialization is utilization to the greatest advantage. In the country the raw material is produced and extracted; in the city it is manufactured and exchanged. Manufacture and exchange require more frequent and quicker contacts than production and extraction; and therefore city land is employed more intensively and is more productive and valuable.

But the tendency of concentration is to increase. More intensive use augments the return from a given area of land; this adds to its value; and in the endeavor to obtain a return proportionate to this greater value the use is made still more intensive, and so on in the vicious circle. Thus undue concentration becomes congestion, clogging movement instead of facilitating it, to the injury not only of business and industry but of living conditions as well. The public and semi-public features of a city-its streets, transit facilities, sewers, parks, etc. are of necessity planned and constructed for a certain intensity of use. It is mainly the bulk of the structures of the city that are privately owned and used-the houses where the people live and the stores and factories where they work-that determines the amount of use to which these public facilities are subjected. If these public features-except as a necessary

The provision is now to be found in the Chicago Code, Callaghan and Co., Chicago, 1911, sec. 450.

For a recent article on height regulation, see "Restrictions Governing City Development" in the (English) Town Planning Review for July, 1921.