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Table of contents

    (Jane Jacobs)1

    One way of bringing people back to cities is by providing housing! Many cities in the US have areas within their downtown cores that have been left underutilized but are increasingly valuable. Because land and housing are incalculable resources in our societies, solutions are needed for building new housing. With a growing interest in city living among younger generations, infill has become key in new housing development.

    Infill Definition

    Infill is the construction of new buildings in underutilized or vacant land lots within urban areas. Infill development is part of "smart-growth" policies to promote densification and the use of existing infrastructure. This is because many cities in the US have an abundance of parking and/or vacant lots that are well-connected to resources such as water, gas, transportation, and emergency services. Infill requires less land conversion, less space, and has the potential to supply new housing and services while decreasing the distances between places.

    Infill development addresses several issues. Suburban sprawl or fringe development has resulted in greater land conversions from green areas or agricultural plots. Major land conversions (from green to urban) lead to environmental degradation and ecosystem disruptions. Additionally, housing stock and affordability are increasingly concerning and cities are seeking to remedy concerns through new construction. Additionally, infill development can increase the local tax base and attract new residents to the city.

    Urban Infill History

    Before understanding infill, it's important to understand how US cities ended up with so many vacant lots in their cities.

    Parking Lots

    There are different kinds of vacant lots in the US. By some statistics, there are eight parking spots for every car, comprising 5% of all urban land use.2 The US expansion of parking lots follows the expansion of car use. After WWII, both the federal government and cities promoted car use and ownership, especially for new, affluent, and primarily white suburban commuters.

    Because suburban residents still needed to commute to cities, major highways were built cutting through cities toward major employers. To further accommodate them, the majority of cities mandated parking requirements at a time of little data when it came to parking. This meant requiring developers and businesses to accommodate cars with arbitrary figures, which at times developed into situations where parking lots are three times the size of buildings.2

    Infill Vacant Lots and Surface Parking in Houston Urban Infill StudySmarterFig. 1 - Vacant Lots and Surface Parking in Central Business District (CBD) in Houston, Texas, Map Data: © 2022 Google; this map doesn't include all the parking garages!

    Currently, parking requirements are still mandated in most zoning codes. Meanwhile, some cities have reduced or scrapped parking requirements altogether because they usually increase housing costs and use the land inadequately. Despite zoning changes, many cities have an abundance of surface parking from decades of enforcement.

    Vacant Lots

    Vacant lots, or unused plots of land, have been found to reduce property values for the entire neighborhood.3 This is in part due to the emotions surrounding urban blight. It invokes the feeling that a place is run-down or abandoned and is headed for decline. Further, these lots decrease tax revenue, while increasing maintenance costs.

    There are multiple reasons for these lots. Since the decline in manufacturing began in the 1960s, many industrial cities (especially in the north) saw populations decrease, with investment and tax bases moving elsewhere. Redlining practices further hampered investments that could have been made by minority groups that remained in inner cities.

    The 2008 Recession disproportionally affected minority groups again, as predatory lending practices led to foreclosures and evictions resulting in higher vacancy rates for homes and units.3 For instance, cities like Detroit, Flint, and Gary, which have high Black resident populations, also have the highest rates of vacant units in the US.4

    Urban blight is the abandonment and deterioration of areas within a city.

    Infill Development Types

    There are different types of infill development that can take place, depending on the size of the lot and the project goal.

    Residential Development

    In residential development, the aim is to increase the housing stock in the area. It usually includes multi-family units (i.e., duplexes and townhomes) focusing on densification in the area. These kinds of units are referred to as missing middle housing. These housing types were built prior to WWII but in recent decades have not been and are, therefore, "missing." They are typically affordable for low- and middle-income families.

    Infill Missing Middle Housing Infill Development StudySmarterFig. 2 - Missing Middle Housing Types. These housing types are usually built during infill development

    Mixed-Use and Transit-Oriented Development

    Mixed-use development is a building with a mix of residential, commercial, entertainment, and other uses. While mixed-use can be applied on a building, block, or street level, usually a singular building with multiple uses is planned using infill. The mixed-use infill is to have homes and services in close proximity to each other which maximizes walking and public transit use.

    Transit-oriented development can benefit from already existing infrastructure and services within cities. Any type of dense housing or mixed-use development within 800 meters of a public transit stop can be considered transit-oriented.

    Occupied Lots: Brownfield and Greyfield Development

    Some abandoned lots may already have existing structures and buildings. Brownfields are previously commercial or industrial areas that are underused or abandoned and may have issues with contamination. Brownfield development will usually require clean-up and site treatment to be deemed safe to use.

    Greyfields are similarly underused or abandoned buildings that were previously commercial or retail spaces. Unlike brownfields, greyfields usually don't have contamination issues but may need investment to replace or renovate buildings.

    An interesting example of greyfields are abandoned malls, also termed "dead malls." Malls were a pillar of US suburban living starting in the 1950s and were built rapidly for the growing middle class. After a few decades, several issues arose. First, too many malls were built close to each other which created competition between them. Second, many local, independent shops (aka "mom-and-pop" shops) closed down as malls, rather than the street or square, became the center of community living . Since the 2000s, consumer habits have turned away from major department stores and towards online retail shopping. Based on some reports, around a quarter of existing malls will close in the next few years (over 1,000!).

    Infill Housing: Barriers and Critiques

    There are a few documented barriers and critiques to infill development, especially housing development. Community members perceive infill as inviting noise and traffic, as well as lowering property values. Because some cities waive parking requirements, local residents fear parking competition for remaining spots. Although some concerns are valid, most of the evidence on infill housing development indicates that property values increase after construction.4

    However, this comes at a cost. Developers tend to set property values at higher rates to collect greater revenue.5 This can hinder the goal of providing affordable housing and may require greater government involvement in planning processes.

    Infill Infill Development Infill Housing StudySmarterFig. 3 - Infill Development. The aesthetic architecture of infill development should match the surrounding character of the area

    Urban Infill Examples

    Urban infill projects range in size from small housing units within a single plot to major redevelopment projects with thousands of acres of land.

    Oakland, California

    Oakland is experiencing issues of housing affordability and displacement due to gentrification. Historically, Oakland was a site for redlining, which until the 1970s prevented Black and other minority residents from obtaining home loans and financing. Without financial services available, urban decay took place in the form of abandoned lots and homes.

    As part of a solution to address gentrification, the city is investing in its affordable housing stock. A recent housing project was Madison at 14th Apartments, built over a former surface parking lot in the city. It has mixed-use elements, with shops and restaurants at the street level. It provides affordable housing while also offering services to former foster care youth.

    Central Park, Denver, Colorado

    Stapleton International Airport was previously Denver's main airport hub until 1995 when Denver's International Airport opened. This provided over 4,500 acres left for redevelopment from the old airport. The Stapleton Development Foundation was founded to plan a new community with diverse housing options. A mix of office, retail, and parks are distributed throughout with high-quality pedestrian infrastructure to promote walkability.

    It's one of the largest infill projects in the US, and has received awards from the Environmental Protection Agency (EPA) and the Stockholm Partnerships for Sustainable Cities Award given by the King of Sweden. The reuse of existing infrastructure and infilling of unused areas provides a great example of greyfield infill development.

    Infill Stapleton International Airport Urban Infill Examples StudySmarterFig. 4 - Stapleton International Airport, Denver (1966). Over 30 000 residents now live in an area that was previously an airport

    Infill - Key takeaways

    • Infill is the construction of new buildings in underutilized or vacant land lots within urban areas.
    • Infill in cities addresses issues with suburban sprawl, housing stock, housing affordability, and local tax base sources.
    • Infill development types include residential, mixed-use, transit-oriented, brownfield, and greyfield development.
    • Successful urban infill development requires the support of the community, local city governments, and developers.


    1. Jacobs, J. The Death and Life of Great American Cities. Random House. 1961.
    2. Overstreet, K. "When 5% of the United States is Covered By Parking Lots, How Do We Redesign our Cities?" ArchDaily. Feb 1, 2022.
    3. Sisson, P. "Blight and vacant land are a national crisis for smaller cities." Curbed. June 25, 2019.
    4. Mallach, A. "The Empty House Next Door: Understanding and Reducing Vacancy and Hypervacancy in the United States." Lincoln Institute of Land Policy. Policy Focus Report. 2018.
    5. McConnell, V., Wiley, K. Chapter 21: Infill Development: Perspectives and Evidence from Economics and Planning. The Oxford Handbook of Urban Economics and Planning, Oxford Handbooks. 2012. DOI: 10.1093/oxfordhb/9780195380620.013.0022.
    6. Fig. 3, Infill Development (, by Stephen Craven (, licensed by CC-BY-SA.2.0 (
    7. Fig. 4, Stapleton International Airport (, by Robert J. Boser, licensed by CC-BY-SA-3.0 (
    Frequently Asked Questions about Infill

    What is infill development?

    Infill development is the construction of new buildings in underutilized or abandoned land lots within urban areas. 

    What is an example of an infill?

    An example of infill is the Stapleton International Airport which was redeveloped into Central Park in Denver, Colorado.  

    What is an infill house?

    An infill house is a form of residential development in the form of multi-family units. 

    What is an urban infill project?

    An urban infill project is the construction or redevelopment of underutilized land lots within cities.  

    Why is infill development important? 

    Infill development is important as issues with suburban sprawl, housing stock, housing affordability, and local tax base sources arise. 

    Test your knowledge with multiple choice flashcards

    Infill development addresses issues with...

    The presence of many abandoned or vacant lots can contribute to...

    Mixed-use and transit-oriented development are common forms of infill development. 


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