Building heights and critical problems of
plot-ratios
by LÉON KRIER
Two sections in ARCHITECTURE: CHOICE OR FATE,
Andreas Papadakis Publisher, Windsor, England, 1998, pages
156-161.
The most beautiful and pleasant cities which survive in the world today have all been conceived with buildings of between two and five floors.
There is no ecologically defensible justification for the erection of utilitarian skyscrapers; they are built for speculation, short-term gain or out of pretentiousness.
Figure 1. Limited building height. Maximum realization of rentable floors implies minimum ceiling height, generating a uniform skyline.
Paradoxically, the imposition of a universal height limit for buildings of between two and five floors does not exclude very tall buildings or monumental buildings. St. Paul's Cathedral in London is a skyscraper on one level. The Eiffel Tower has only three floors. The Capitol in Washington, Nôtre-Dame de Paris, the Forbidden City in Beijing and even the Seven Wonders of the World respected these limits. The universal limitation of building heights to between two and five stories would both protect historic centers threatened with overdevelopment and at the same time encourage the redevelopment of the suburbs. Instead of inflating the cost of buildings in the center, such a limitation would contribute to an increase in property values in those areas that remain arbitrarily undervalued.
Figure 2. Limited number of floors. No height limit implies maximum variation of building's ceiling height, generating a varied skyline.
Thus, building heights should not be limited metrically (such regulations are always arbitrary and lead to a stultifying uniformity) but by the number of floors -- between two and five, depending on the character of the village or city, the nature, status and use of the building, the width of roads and squares, and the prestige of the site. It should be observed, moreover, that building-technology, servicing and conception change radically (separation of structure and wall construction, lifts, expensive services, fire protection, etc.) for buildings of more than five floors. In addition, a limit on the number of floors permits an evident and natural differentiation between public and private uses, between symbolic and utilitarian character, and between monumental and domestic architecture.
Figure 3. Low buildings and high ceilings.
Figure 4. High buildings and low ceilings.
Historic cities rarely surpass a plot ratio of 2:1 (ratio of floor area to plot area). This density is easily achieved by buildings not exceeding three to five floors, allowing well lit and humanely proportioned private gardens and public spaces. Since the nineteenth century we have observed with each new revision of land-use plans a regular, irreversible increase in plot-ratios (in the City of London, for instance, the coefficient regularly exceeds 6:1). This excessive density leads to the functional and general congestion of historic centers. Streets become gloomy, noisy corridors and private gardens shrink to dank service yards. The result is the degradation of the concept of the traditional city itself, justifying the exodus to the suburbs.
Figure 5. Conservation versus overdevelopment.
If authorities allow developers to exceed the critical point of five floors, the value of building plots rises astronomically, which in turn creates more pressure for higher and higher densities. It is a vicious circle which, in the long term, leads to an insidious "Manhattanism" and represents the financial overexploitation of the land of the city whose unavoidable structural bankruptcy must in the end be paid for by public funds. Conservation areas are, by definition, those areas that have achieved optimum density both in form and appearance. It is complete nonsense to increase plot-ratios in these sectors. Such decisions ensure that the real estate value of a listed building becomes indefensible in face of the potential added value of denser redevelopment. Consequently, increases in plot-ratios regularly defeat even the staunchest conservation policies.