16 May 2013


A simple solution to high rents and long commutes in cities was invented a century ago: building up. But San Francisco is restricted vertically to an extreme degree. Why? It’s not seismic issues, it’s a density limit called Prop M. Why do we limit our cities vertically in this way?

The need for horizontal restraint is obvious: Society needs to define streetscapes, block sizes and green areas to decompress in. Building codes were established to bring some discipline into the city. It brought fire safety to London. But it also started to strangle the vertical dimension: As a byproduct it capped building up.

Zürich, Switzerland strains against a four-and-a-half story planning limit like steam in a pressure cooker. It sprawls outward and unravels at the edges, the rents in the undersupplied housing market spiraling. Only conglomerates of banks and real estate have the influence to get special permits and pierce the ceiling. They in turn don’t build sorely needed densification. They construct glass monuments to their cause like the Prime Tower, totally disregarding the urban surroundings and further intensifying the market.

Once a horizontal plan is established, building height should reflect demand, constrained only by the solidity of the ground beneath. Manhattan was planned this way: grid design, geological surveys, rough volumetric limits. Bedrock differences led to flatter Midtown and taller Downtown - but the planners understood that arbitrating height is as difficult as predicting the gold-market for the next hundred years. Wrong bets blow rents out of proportion and push the poor to the edges of the city. Micromanaging zoning height uses up valuable effort that could have gone into horizontal planning (ahem, bike lanes?).

Focusing on the horizontal dimension may let us up the quality and speed of urban planning. Quality of life could greatly increase on the street level, as the necessary density for an urban experience would be established. Unchecked verticality may also reduce horizontal movement, shortening commutes. Urban planning should be horizontal agreements, not height regulation. Plan the horizontal, let the vertical do what is needed. Image by Guy Carlton Wiggins