Mixed-use development is the practice of allowing more than one type of use in a building or set of buildings. In planning zone terms, this can mean some combination of residential, commercial, industrial, office, institutional, or other land uses.

History

Throughout most of human history, the majority of human settlements developed as mixed-use environments. Walking was the primary way that people and goods were moved about, sometimes assisted by animals such as horses or cattle. Most people dwelt in buildings that were places of work as well as domestic life, and made things or sold things from their own homes. Most buildings were not divided into discrete functions on a room by room basis, and most neighborhoods contained a diversity of uses, even if some districts developed a predominance of certain uses, such as metalworkers, or textiles or footwear due to the socio-economic benefits of propinquity. People lived at very high densities because the amount of space required for daily living and movement between different activities was determined by walkability and the scale of the human body. This was particularly true in cities, and the ground floor of buildings was often devoted to some sort of commercial or productive use, with living space upstairs.

This historical mixed-used pattern of development declined during industrialisation in favor of large-scale separation of manufacturing and residences in single-function buildings. This period saw massive migrations of people from rural areas to cities drawn by work in factories and the associated businesses and bureaucracies that grew up around them. These influxes of new workers needed to be accommodated and many new urban districts arose at this time with domestic housing being their primary function. Thus began a separating out of land uses that previously had occurred in the same spaces. Furthermore, many factories produced substantial pollution of various kinds. Distance was required to minimize adverse impacts from noise, dirt, noxious fumes and dangerous substances. Even so, at this time, most industrialized cities were of a size that allowed people to walk between the different areas of the city.

These factors were important in the push for Euclidian zoning premised on the compartmentalization of land uses into like functions and their spatial separation. In Europe, advocates of the Garden City Movement were attempting to think through these issues and propose improved ways to plan cities based on zoning areas of land so that conflicts between land uses would be minimized. Modernist architects such as Le Corbusier advocated radical rethinking of the way cities were designed based on similar ideas, proposing plans for Paris such as the Plan Voisin, Ville Contemporaine and Ville Radieuse that involved demolishing the entire center of the city and replacing it with towers in a park-like setting, with industry carefully sited away from other uses.

In the United States, another impetus for Euclidian zoning was the birth of the skyscraper. Fear of buildings blocking out the sun led many to call for zoning regulations, particularly in New York City. Zoning regulations, first put into place in 1916, not only called for limits on building heights, but eventually called for separations of uses. This was largely meant to keep people from living next to polluted industrial areas. This separation however, was extended to commercial uses as well, setting the stage for the suburban style of life that is common in America today. This type of zoning was widely adopted by municipal zoning codes.

With the advent of mass transit systems, but especially the private automobile and cheap oil, the ability to create dispersed, low-density cities where people could live very long distances from their workplaces, shopping centres and entertainment districts began in earnest. However, it has been the post-second World War dominance of the automobile and the decline in all other modes of urban transportation that has seen the extremes of these trends come to pass.

Benefits

Throughout the late 20th century, it began to become apparent to many urban planners and other professionals that mixed-use development had many benefits and should be promoted again. As American, British, Canadian and Australian cities deindustrialized, the need to separate residences from hazardous factories became less important. Completely separate zoning created isolated "islands" of each type of development. In most cases, the automobile had become a requirement for transportation between vast fields of residentially zoned housing and the separate commercial and office strips, creating issues of Automobile dependency. In 1961, Jane Jacobs' influential The Death and Life of Great American Cities argued that a mixture of uses is vital and necessary for a healthy urban area.

Zoning laws have been revised accordingly and increasingly attempt to address these problems by using mixed-use zoning. A mixed use district will most commonly be the "downtown" of a local community, ideally associated with public transit nodes in accordance with principles of Transit-oriented development (TOD) and New urbanism. Mixed use guidelines often result in residential buildings with streetfront commercial space. Retailers have the assurance that they will always have customers living right above and around them, while residents have the benefit of being able to walk a short distance to get groceries and household items, or see a movie.

Drawbacks

Mixed use development is seen as too risky by many developers and lending institutions because economic success requires that the many different uses all remain in business. Most development throughout the mid to late 20th century was single-use, so many development and finance professionals see this as the safer and more acceptable means to provide construction and earn a profit. Christopher B. Leinberger notes that there are 19 standard real estate product types that can obtain easy financing through real estate investment trusts. Each type, such as the office park and the strip mall, is designed for low density, single use zoning. Another issue is that short term discounted cash flow has become the standard way to measure the success of income-producing development, resulting in "disposable" suburban designs that make money in the short run but are not as successful in the mid to long term as walkable, mixed use environments.

Mixed use commercial space is often seen as being best suited for retail and small office uses. This precludes its widespread adoption as the trend to ever-larger corporate and government employment accelerates.

Mixed use residential buildings and neighbourhoods are best suited to those who prefer public amenities to private space. The lack of private outdoor space for kids and pets is anathema to some, particularly in some North American and Australian cultures.

Construction costs for mixed-use development currently exceed those for similar sized, single-use buildings. Challenges include fire separations, sound attenuation, ventilation, and egress. Leinberger explains,

Good urban architecture costs upward of 50 percent more than typical suburban buildings. In urban areas, residents and businesses demand a higher quality of building, since you are walking past them, not driving by at 45 miles an hour with the buildings set back 150 feet.

Additional costs arise from meeting the design needs: In some designs, the large, high-ceilinged, columnless lower floor for commercial uses may not be entirely compatible with the smaller scale of walled residential space above. Often the parking space requirements for businesses exceed those of residential development. Thus, mixed use projects that are not sited close to public transit are likely to require a large number of parking spaces that may be difficult to finance. It should be noted however that in mixed-use developments in some denser areas, owning an automobile might be considered a luxury rather than a necessity. A notable example in the United States is Manhattan, though this is an atypical case.

Others maintain that modern consumers prefer big box retailers, as evidenced by the fact that most grocery shoppers today would prefer the convenience of weekly shopping, as opposed to picking up each day's food items from a number of local shops.

Mixed use of non-habitable structures

Also expansive non-habitable structures as tall towers are often used for multiple purposes, which can be described also as "mixed-use". So it is not uncommon, that a water tower has an observation deck and is used for telecommunication purposes or that an observation tower is also used for telecommunication purposes. Most radio towers are designed to carry antennae for multiple purposes and may sometimes also carry equipment for meteorological measurements. Electricity pylons sometimes also carry antennas for mobile phone services.

Limitations to mix use of non-habitable structure result from their static properties, interference of users and maintaibiity. So in most cases a mast radiator insulated against ground is only used for one transmitter, although it is technically possible to mount antennas for UHF/VHF-services and meteorological instruments on it. However maintenance of them may get difficult, as the transmitter using the mast radiator may be switched off or use a spare antenna, when maintenance is done.

See also

• Activity centre
• Automobile dependency
• Edge city
• New Mobility Agenda
• New Urbanism
• Principles of Intelligent Urbanism
• Smart Growth
• Sustainable development
• Transit-oriented development
• Urban Design
• Urban Sprawl

External links

• Urban Markets Strengthen, But Standard Real Estate Products Are Not Suited for Mixed-Use, Leinberger
• The Option of Urbanism - Back to the future for Metro Vancouver, (video of lecture by Christopher B. Leinberger, April 2008)