Topic 6.6 Notes – Density and Land Use

What Residential Density and Residential Land Use Are

Residential density measures housing or residents on residential land.

$$\text{Residential density}=\frac{\text{dwelling units or residents}}{\text{residential land area}}$$

That formula matters, but AP Human Geography usually cares more about what density looks like on the landscape.

• Residential land use means land used for housing. This topic stays with housing, not commercial or industrial land.
• Population density means people per area. That is broader than housing form.
• Housing density means dwelling units per area.
• Crowding means too many people inside living space. A place can be dense without being crowded.
• Building height does not automatically mean highest density. Widely spaced towers can be less dense than tightly packed rowhouses.

Low, medium, and high density are relative. What counts as high density in one metro area might feel ordinary in another. The main AP idea is that residential landscapes show culture, technology, development cycles, infilling, and power.

Low-, Medium-, and High-Density Housing

Low density

Low-density housing spreads households over more land.

• Detached single-family homes on separate lots
• Yards, setbacks, driveways, garages, cul-de-sacs
• Common in suburbs and metro fringes
• Usually tied to car dependence and separation from jobs and shopping

The standard example is postwar U.S. suburbanization. Highways, mortgage finance, mass car ownership, and single-family zoning helped create large low-density suburbs.

Medium density

Medium density fits more households in without relying on tall towers.

• Duplexes, triplexes, semidetached houses
• Townhouses, rowhouses or terraced houses
• Courtyard housing and low-rise apartments
• Smaller lots, attached walls, continuous street frontage

These often appear in older neighborhoods, transition zones, and transit corridors. Philadelphia, Baltimore, London, and Amsterdam are classic rowhouse examples. A tightly packed rowhouse district can reach substantial density even without skyscrapers.

A key test point is that rowhouses can be denser than tall buildings spaced far apart.

High density

High-density housing puts many households on little land, often through vertical building.

• Mid-rise and high-rise apartments or condos
• Many units per parcel
• Shared halls, elevators, and open space
• Little private yard space

You often see this near CBDs, transit stations, and major corridors because accessible land is expensive. Hong Kong is the standard example. Mountainous terrain limits buildable land, high land values push intense use, and rail transit plus elevator and steel construction make towers practical.

Why Density Varies Across a City

Cities do not have one single density. Density shifts because different parts of the city have different costs, access, and rules.

A classic way to visualize this is the bid-rent model, which shows why the most accessible land near the CBD tends to be used most intensively.

Bid-rent model of urban land use

• Accessibility and land value shape a density gradient. More accessible land costs more, so developers build more intensively there.
• Transportation changes form over time. Walking cities were compact. Streetcars and rail stretched growth along corridors. Cars and highways encouraged low-density sprawl. Transit today can support dense station-area housing.
• Physical geography matters. Mountains, wetlands, coasts, and limited buildable land can force density upward. Flat open land makes outward expansion easier.
• Zoning and regulation can block or allow density. Height limits, minimum lot sizes, setbacks, parking requirements, and multifamily bans directly shape what gets built.
• Development history leaves visible layers. Streetcar-era districts are often denser and more connected. Auto-era districts usually have detached homes, garages, and curving roads.

Infilling, Redevelopment, and Densification

These terms get mixed up a lot, so keep them separate.

• Infill means adding housing on vacant or underused land inside an already built-up area.
• Densification means increasing housing units or population within an existing area.
• Redevelopment means replacing or heavily changing an existing use. It can include infill, but they are not the same thing.

Ways density increases include apartments on empty lots, housing on old parking lots, dividing big homes into multiple units, adding accessory dwelling units, or replacing small buildings with larger multifamily ones. AP often contrasts this inward growth with outward fringe expansion.

What Density Reveals on Maps and in the Built Landscape

On maps and images, low density shows large lots, spacing, yards, and parking. Medium density shows attached walls, smaller parcels, and continuous blocks. High density shows many units, vertical form, and limited private open space.

Before interpreting data, check what the map actually measures. It might show persons per area, dwelling units per area, or building heights. Also check scale. A city average can hide huge neighborhood differences.

Density patterns show values about privacy, mobility, family life, and public space. They also show power through zoning, transit investment, preservation, and decisions to approve or block higher-density housing.