In urban planning, infill is the introduction of new land uses such as housing.
Urban infill 
In the urban planning and development industries, infill is the use of land within a built-up area for further construction, especially as part of a community redevelopment or growth management program or as part of smart growth. It focuses on the reuse and repositioning of obsolete or underutilized buildings and sites. This type of development is essential to renewing blighted neighborhoods and knitting them back together with more prosperous communities. Redevelopment or land recycling is development that occurs on previously developed land. Infill buildings are constructed on vacant or underutilized property or between existing buildings.
Chatham Square 
Chatham Square, in Alexandria, Virginia, is the site of mixed-used redevelopment. Improvements were made to the historic houses to make for affordable housing for its residents. The newly improved square in "Old Town" is meant to emulate its historical beginnings while utilizing modern architecture. The usable open-space for residents includes parking, central courtyards, and an improved streetscape. The integration of public, mixed-income housing was not only made for the existing community, but also the surrounding neighborhood. Chatham Square maintained its former street design and added green space. Urban infill is synonymous with trying to uphold the original style while improving the community.
Challenges to urban infill 
Although urban infill is an appealing tool for community redevelopment and growth management, it is often far more costly for developers to develop land within the city than it is to develop on the periphery, in suburban greenfield land. Costs for developers include acquiring land, removing existing structures, and testing for and cleaning up any environmental contamination.
Scholars have argued that infill development is more financially feasible for development when it occurs on a large plot of land (several acres). Large scale development benefits from what economists call economies of scale, and reduces the surrounding negative influences of neighborhood blight, crime, or poor schools. However, large scale infill development is often difficult in a blighted neighborhood for several reasons. These include the difficulties in acquiring land and in gaining community support.
Amassing land is one challenge that infill development poses that greenfield development does not. Neighborhoods that are targets for infill often have parcels of blighted land scattered among places of residence. Developers must be persistent in order to amass land parcel by parcel, and often find resistance from landowners in the target area. One way to approach this problem is for city management to use eminent domain to claim land. This is often unpopular among city management, as well as among neighborhood residents. Developers must deal with regulatory barriers, visit numerous government offices for permitting, interact with city management that is frequently unwilling to use eminent domain to remove current residents, and generally engage in public-private partnerships with local government.
Developers also meet with high social goal barriers in which the local officials and residents are not interested in the same type of development. Although citizen involvement has been found to facilitate the development of brownfield land, residents in blighted neighborhoods often want to convert vacant lots to parks or recreational facilities, whereas external actors seek to build apartment complexes, commercial shopping centers, or industrial sites .
Suburban infill 
Suburban infill describes the development of land in existing suburban areas that was left vacant during the development of the suburb. It is one of the tenets of the New Urbanism and smart growth trends of urging densification to reduce the need for automobiles, encourage walking, and ultimately save energy. One exception to this is the practice of urban agriculture, in which land in the urban or suburban area is retained to grow food for local consumption.
The Village of Ponderosa in West Des Moines, Iowa is a good example of suburban infill. It was formerly a 9-hole golf course surrounded by suburban West Des Moines businesses and tract homes, but starting in 2006 it was redeveloped into a higher-density mixed-use community with a pedestrian friendly retail center.
Infill housing 
Infill housing is the insertion of additional housing units into an already approved subdivision or neighborhood. These can be provided as additional units built on the same lot, by dividing existing homes into multiple units, or by creating new residential lots by further subdivision or lot line adjustments. Units may also be built on vacant lots.
Infill residential development does not require the subdivision of greenfield land, natural areas, or prime agricultural land. Existing infrastructure may in some cases need little expansion for utility and other services.
As with other new construction, structures built as infill may clash architecturally with older, existing buildings.
See also 
|Wikimedia Commons has media related to: Urban infills|
- Infill Philadelphia
- Southeast Tennessee Development District, Chattanooga, TN. "Green Infrastructure Handbook." January 2011
- Porter, Michael (May/June 1995). "The Competitive Advantage of the Inner City". Harvard Business Review: 55–72.
- Farris, J. T. (2001). "The barriers to using urban infill development to achieve smart growth". Housing Policy Debate 12 (1): 1–30.
- Greenberg, M; M. J. Lewis (2000). "Brownfields Redevelopment, Preferences and Public Involvement: A Case Study of an Ethnically Mixed Neighbourhood". Urban Studies Routledge 37 (13): 2501–2514.
- Village of Ponderosa: West Des Moines Real Estate, Homes Condos Lofts & Retail
- Zirkle, Jon. "Chatham Square". Congress for the New Urbanism. Retrieved 29 March 2012.
- PDF (109 KiB)
- PDF (3.54 MiB)
- Denver Infill.com - a comprehensive overview and photographic survey of all the urban infill and redevelopment projects in the greater Downtown Denver area