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Urban Design

Principles of Good Urban Design

Good Design Principles, such as those below crafted by the American Institute of Architects, should guide ALL development. 

Urban areas, however, have particular characteristics that require very different solutions from those usually seen in the suburbs.  It is these unique urban qualities that make downtowns and center city neighborhoods attractive to residents and shoppers in the first place.  If we allow these urban qualities to be replaced by suburban solutions, the downtown loses its competitive advantage and begins to look like every other place.

A more detailed list of Guidelines for Chattanooga’s downtown and urban neighborhoods follows these general Principles.
 

AIA’s 10 Principles for Livable Communities

www.aia.org/livable

1. Design on a Human Scale
Compact, pedestrian-friendly communities allow residents to walk to shops, services, cultural resources, and jobs and can reduce traffic congestion and benefit people's health.

2.
Provide Choices
People want variety in housing, shopping, recreation, transportation, and employment. Variety creates lively neighborhoods and accommodates residents in different stages of their lives.

3.
Encourage Mixed-Use Development
Integrating different land uses and varied building types creates vibrant, pedestrian-friendly and diverse communities.

4.
Preserve Urban Centers
Restoring, revitalizing, and infilling urban centers takes advantage of existing streets, services and buildings and avoids the need for new infrastructure. This helps to curb sprawl and promote stability for city neighborhoods.

5.
Vary Transportation Options
Giving people the option of walking, biking and using public transit, in addition to driving, reduces traffic congestion, protects the environment and encourages physical activity.

6.
Build Vibrant Public Spaces
Citizens need welcoming, well-defined public places to stimulate face-to-face interaction, collectively celebrate and mourn, encourage civic participation, admire public art, and gather for public events.

7.
Create a Neighborhood Identity
A "sense of place" gives neighborhoods a unique character, enhances the walking environment, and creates pride in the community.

8.
Protect Environmental Resources
A well-designed balance of nature and development preserves natural systems, protects waterways from pollution, reduces air pollution, and protects property values.

9.
Conserve Landscapes
Open space, farms, and wildlife habitat are essential for environmental, recreational, and cultural reasons.

10.
Design Matters
Design excellence is the foundation of successful and healthy communities.
 

The following Design Guidelines for Chattanooga’s downtown and urban neighborhoods are organized into 5 general development topics.

Land Use Patterns

Site Design

Building Design

Signs

Residential Buildings

 

Land Use Patterns

Mixed Use
A mix of uses should be provided within each development site and within each building in order to bring daily activities within walking distance, reduce the number and length of automobile trips, and establish densities that support the use of transit and neighborhood stores.

Neighborhood Commercial Centers
Neighborhood commercial uses should generally be clustered at intersections and built at a scale that does not overwhelm the residential uses.

Walkability
Residences should be located within a quarter-mile of commercial centers that include schools, jobs, and shopping to encourage walking.   Transit stops should also be located in these commercial centers.

Density
Residential areas should achieve a minimum density of 12 units per acre to support transit use.

 

SITE DESIGN

Setbacks
Commercial buildings in the urban area should be built to the sidewalk to maintain the street edge and create interest for the pedestrian.  If an outdoor café or other pedestrian activity is provided in front, buildings may have a deeper setback. Under no circumstances should parking be placed between the front of the building and the street. For corner buildings, both facades should be built to the sidewalk.

Street Edges
If a building is not built to the sidewalk, a 3 to 4-foot masonry wall or decorative fence with landscaping should be built along the right-of-way to maintain the urban street edge.

Parking & Vehicular Access
Parking lots fronting the street create “dead spots” in the urban fabric and too many surface parking lots along a street can actually discourage pedestrian travel.  Parking should be located behind buildings and alleys should be used for vehicular access.  A mid-block cut-through can provide pedestrian access.

If parking behind the building is physically impossible, parking may be placed to the side of the building, but only if it is screened from view with a 3 to 4-foot masonry wall or decorative fence and landscaping along the sidewalk to maintain the street edge.

The number of parking spaces should be limited to promote the use of transit in the urban area.  Shared parking is encouraged.

Drive-through windows create safety conflicts with pedestrians and should not be used in the urban area unless they are located behind the building and a side street or alley is used for vehicular access.

Curb cuts (driveways) should not be located on Broad, Market, 4th, Frazier, M.L.King, Main and other major streets in the Downtown.  They create safety conflicts with pedestrians.  Alleys or secondary streets should be used for vehicular access.

All multi-story parking garages should include retail or offices on the ground floor to increase pedestrian activity.

Landscaping / Trees
A tree canopy cover of 15% or greater is necessary in the urban area to provide shade, reduce urban heat build-up, and filter pollutants from the air and stormwater.  All parking lots should include at least one tree for every five parking spaces to achieve this goal.

Stormwater
Stormwater runoff should be minimized, but engineered stormwater facilities should not be visible from the street.  Stormwater retention and detention areas should be located to the rear of buildings and designed in a naturalistic way whenever possible.

Pervious paving is encouraged on all parking lots to reduce stormwater runoff.

Sidewalks
Sidewalks in commercial areas should be at least 10 feet wide to allow room for pedestrians to pass. 

Sidewalks in residential areas should be at least 5 feet wide with a planting strip between the sidewalk and the street to accommodate trees and to provide some barrier between pedestrians and moving cars.

Sidewalk cafes help animate urban areas, but they must be designed to allow sufficient room for pedestrian travel along the sidewalk.  A minimum clear zone of 6 feet is required for handicap access, but 10 feet is preferred in highly traveled areas.  For cafes with a substantial numbers of chairs or for those that serve alcohol, a decorative fence is needed to delineate the public realm from the private commercial space.

Streetscape
For commercial streets, street trees should be located in tree wells along the curb edge of the sidewalk.  Consult the Design Studio or Public Works Department for appropriate spacing and species of trees.

For residential streets, street trees should be located in a continuous planting strip along the curb edge of the sidewalk. This planting strip should be a minimum of 4 feet wide. 

Pedestrian lights, planters, waste receptacles, and other street furniture should line up with the trees to leave ample walking room for pedestrians.

Lighting
Lighting should be used to make an area attractive and safe, but should not create light pollution or excessive glare.

The mounting height of parking lot lighting should not exceed 20 feet.

All exterior lighting should include full cut-offs to direct light downward.

Screening
All dumpsters and mechanical equipment should be located behind the building and should be screened from view with an opaque fence, wall or landscaping.

Open space
Open space should be used to create public gathering spaces and to protect environmentally sensitive areas.  Development should not occur on steep hillsides (slopes over 25%) or within floodplains.

A 100-foot “no build” zone should be maintained along the Tennessee River and all creeks to accommodate extensions of the Riverwalk and greenways and to provide a natural buffer.

Parks and plazas should incorporate fountains, public art, attractive shelters, and seating.

 

Demolitions
To maintain the continuity of the street edge and urban fabric, the demolition of buildings should be avoided until redevelopment plans are approved.

 

BUILDING DESIGN

Green Buildings
Building designers should strive for L.E.E.D. (Leadership in Energy and Environmental Design) certification to increase energy efficiency, reduce stormwater runoff, and minimize waste.  Consult the U.S. Green Building Council (www.usgbd.org) or www.greenspaceschattanooga.com for more information.

 

Historic Buildings
Buildings more than 50 years old are considered historic and should be preserved.  For more information, contact Chattanooga’s Public Works Department at http://www.chattanooga.gov/Public_Works/70_HistoricPlanning&DesignReview.htm

or Cornerstones at www.cornerstonesinc.org

Historic buildings should only be demolished if:

  1. Public safety requires the building’s removal; or
  2. The building has lost its architectural and historic value and removal of the building will improve the appearance of the area.

Building Height & Mass
Buildings should establish a well-defined street edge and urban character and respect the pedestrian scale.

The city’s tallest buildings should be located in the downtown core to maintain densities necessary to support transit and to maximize economic development potential.  Building heights in locations further from the core should decrease to maintain compatibility with their surroundings.

  

Commercial streets should accommodate higher densities, and therefore taller buildings, than predominantly residential streets.

Corner buildings may have a slightly greater height and mass than surrounding buildings to “anchor” the street corner.

Buildings should be similar in height and configuration to nearby buildings on the same street. 

A “building height to street width” ratio between 1:2 and 1:1 is necessary for good street spatial definition.  Commercial buildings should be at least 2 stories to frame the street and provide for a potential mix of uses.

Roofs
Roofs should reflect traditional urban commercial patterns and provide some visual interest to the tops of buildings, but should not overwhelm the street facade.

For commercial buildings, flat roofs with a decorative cornice are encouraged.  Hipped and front-gabled roofs are acceptable, but shed roofs (single pitch) and mansard-style elements attached to the building facade are not acceptable.

Occupied roofs, such as roof gardens and terraces are encouraged.

Facades
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Building facades should reflect traditional urban patterns and provide interest for the pedestrian.

Each building should have an identifiable base, middle, and top to create pedestrian interest at the street level and to cap the building.

Long uninterrupted horizontal stretches of facades should be avoided.  Building bays, storefront, entrances, columns, and other vertical elements should be used to “break up” the building façade.

Storefronts should include display windows, transoms, awnings, and entrances.

Horizontal elements – windows, cornice lines, stringcourses - should be generally aligned with those of adjoining buildings.

Doors & Windows
Openings and bays should reinforce the human scale, maintain traditional urban patterns, and provide interest for the pedestrian.

The ground floor of all commercial buildings should contain at least 50% openings.

Heavily tinted windows should not be used as they create the appearance of the building being empty.

Window frames (except glass block) should always be recessed at least 2 inches from the building face to create some depth and shadow on the façade.

Pedestrian Access
The primary pedestrian entrance should be located along the primary street to encourage pedestrian activity.

Materials
Exterior materials should reflect a sense of permanence and urban character.  Materials such as brick, split face concrete block, concrete block finished with stucco, and stone are preferred.

Metal buildings are not appropriate.  Metal siding may be used sparingly as an architectural element.

Mechanical Equipment
Mechanical equipment should be screened from the public right-of-way whether located on the ground or on the roof.

 

SIGNS

Signs should balance the need to market individual businesses with the objectives of maintaining traditional urban patterns and minimizing visual clutter.  A rule of thumb for the size of signage on an individual facade is 1.5 square feet of signage for every linear foot of that building side.

Signs should be located in the lintel or sign frieze that separates the ground level from the upper façade, on the upper façade walls, or projecting from the face of the building.

Internally illuminated box-type signs are not appropriate.  Individually illuminated letters are more appropriate.

Awnings and banners should be designed as an integral part of the building signage.

Roof signs, billboards, and other off-premise signs are not appropriate.

 

RESIDENTIAL BUILDINGS

Elements such as building setbacks and parking for residential uses are often different from those for commercial development.

Residential Parking
Parking for residential uses should be located behind the primary residence and accessed from an alley to maintain pedestrian safety on the primary streets.  If alley access is not possible, shared driveways should be use to limit the number of curb cuts and the amount of paving.

Garage doors should not face the public street.  A street vista of garage doors does not create an appealing pedestrian environment.

Residential Setbacks
Residential buildings may be set back from the sidewalk to allow front porches, stoops, and small landscaped areas.

Residential building setbacks should be consistent along the same street to establish a continuous street edge.

 Porches
Townhouses and single-family homes should include porches and stoops to encourage interaction between residents and pedestrians.  Porches should be deep enough (8 feet) to accommodate seating.

Residences should be elevated at least 2 feet from the ground level to provide some privacy from the street.
 

 
Development Resource Center, Suite 2000
1250 Market Street 
Chattanooga, Tennessee 37402


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