On the left, we see incremental intensification: each lot is allowed to redevelop as its owner sees fit. Some of the single family homes turn into duplexes. Some time later, the least intensified lots (the single family homes) might turn into small apartment buildings. The remaining single family homes and duplexes turn into mid-rise apartment buildings.

On the right, we see sudden intensification, of a type that often occurs when the lot-by-lot conversions described above are either illegal according to the zoning code, or infeasible for one reason or another. The only practical action for homeowners is to hold on to their property until a large developer buys them all out and razes the block for a large apartment building (or even worse, the local government might use eminent domain to give private property to a large developer).

Incremental intensification often goes hand in hand with granularity. It keeps land ownership diversified, and it enforces good urban bones, since a separate building every so many feet means a destination such as a housefront or a shopfront every so many feet. It lowers the risk that an area will be negatively transformed, as it takes the form of many small bets (a few apartment buildings will pop up first, and if the demand is not there, no more apartment buildings will appear) rather than fewer large bets (the entire block is being replaced with 200 units). Smaller buildings on smaller lots are easier to redevelop for the next generation of owners and land uses, and facilitating incremental intensification decreases the impact of land speculators. We are always going to have the land speculator who refuses to develop until either the time is right or someone offers them a really large sum of money. I would rather the speculator sit on a few empty lots than entire blocks.

Incremental Implementation

Rarely is our first attempt at something our best attempt. In the diagram below, a city wants to improve a street by planting trees and installing bike lanes.