Why should your city jettison its outdated zoning rules and allow more housing construction on small and irregular lots? Let Alli Thurmond Quinlan count the ways:

"The city that does will see more attainable house price points. It will see more housing units that are a better fit to small-household demographics. This also means it will free up citizen budgets and time such that, instead of spending all your time on a commute and instead of spending all your money on a house that's too big for you, you will have time and capacity and energy to be investing in your community."

Quinlan, an Arkansas-based builder with FlintlockLAB and acting director of the Incremental Development Alliance, regularly works to convince cities of the value of incremental projects and that their zoning practices are hindering a much-needed expansion of housing options.

A large percentage of North American cities embraced restrictive zoning rules in the mid-to-late 20th century. Many of these rules came at a time when suburbs were burgeoning and, unfortunately, they caused cities to forfeit many of the advantages of traditional city development. Compounding the challenge are rules that put some multiunit projects under the commercial code (which is much more expensive) and funding streams that are easily accessible for single-family homes and large multifamily projects, but very little in between.

"As an example, Atlanta, which is very typical of a lot of cities, adopted a new zoning ordinance in the early 1980s and copied a lot of suburban planning standards into our city that were not historically accurate," explains Eric Kronberg. His firm, Kronberg Urbanists Architects, has executed a number of projects that required careful analysis of existing zoning rules and creative solutions.

One example is La France Walk, which added 25 units on 2.5 acres in a "pocket community" in Atlanta. By adding a mix of smaller, semidetached options, Kronberg's firm was able to offer a range of prices from $275,000 to $675,000. Kronberg says those lower price points are critical in the face of an affordability crisis and notes that the one-bedroom units on this and similar projects were among the first to sell. Better still, the success of the project "became the catalyst for me to show our clients that there's a market in this that matters."

Neil Heller has been waging a similar battle in Portland, Oregon, and also emphasized the creativity required to modify or work around zoning statutes. His firm, Neighborhood Workshop, has done projects that he calls "backyard infill," in which smaller, stand-alone dwellings are built on properties with existing houses. This substantially reduces land-acquisition costs and has enabled more affordably priced homes in some of Portland's most popular neighborhoods.

One project that Heller consulted on took a city lot with an existing three-bedroom house and added two smaller, stand-alone dwellings that could be sold separately. This project by developer Noah Rosen put two appealing new residences on the market for well below the going rate for a single-family home in an area that has become out of reach for most middle-class buyers.