Planning for a half-life has interesting implications. For central business districts, it means facing the fact that large-scale, noisy reconstruction of towers becomes a permanent feature, to be mitigated for life to function normally on a day-to-day basis. At the other end of the scale, it means approaching new neighborhoods with the assumption that some lots may never be built on, or some blocks never filled in, if demand or financing evaporates. New neighborhoods can be planned with the option for half of their space to remain unbuilt, making their contribution to the city as green space. This cannot be financed under conventional planning systems, because a development’s construction is intended to be paid for with land sales, and its maintenance with land taxes.

Finally, planning for places with a lifecycle means that the rate of growth of the city expresses itself through planned or unplanned changes. What if the end of a house’s lifespan means city-sponsored demolition, as happens in the “Rust Belt”, following a severe socio-economic disturbance? Or growth pressure is pulling a place up a level or two on the New Urbanist transect due to booming capital flows, as California is seeing? Coming full circle, it means cities need a plan for each neighborhood to go up, down, or the same in their transect zone, instead of assuming that the transect zone itself is the plan that must be encoded and enforced.

Neighborhoods are Destined to Change

Behind the two fracture points of modern planning, NIMBYism and gentrification, is one fundamental question: should neighborhoods change? NIMBYs and anti-gentrification activists agree that they should not. The modern planning system was invented to enforce that agreement.

Introducing change into such a system is to work against its nature. Whether the rules are coming from the national government, the municipal bylaws or property owners’ associations does not matter. What matters is the intent of the rule, to keep things ordered as they are. This is where “accessory dwelling units” get their significance.

We have witnessed a massive conflict emerge over the euphemistic accessory dwelling unit (studio apartment). In jurisdiction after jurisdiction, the pressure of real-estate demand is splitting the constituents: Is this what we want in our backyard to keep rents from rising?

If you wonder whether a struggle to add a few permissions allowing property owners to build studio rentals on their properties is worth the pain, realize what this change implies; it shifts the fundamental question of planning from should our neighborhood change to how should our neighborhood change.

This is not a simple addition of studio rentals but a generational shift in neighborhood planning. When the next generation finds itself occupying a neighborhood filled with studio apartments, there won’t be a need to shift question again, only to provide new answers. Since accessory dwelling units have some of the shortest lifecycles of any dwelling, this change will bear its fruits soon enough to lead to more extensive succession.