Fundamental principles for street trees:
Shade and enclosure

Before: a barren roadway. Photo by Geoffrey Ferrell.

In his 1992 book, Trees in Urban Design, Henry F. Arnold wrote:

"An urban sidewalk without trees is like a building without a roof. Defining streets with buildings or trees to form a continuous, predictable border reinforces the function of the street as a public space and the structure of a community. Trees are a feature that should be appropriately incorporated into every street and avoid conflicts with overhead and underground infrastructure.

"Generally, trees should be planted in straight lines or rows close to the curb in the sidewalk or between the sidewalk and the curb. Following these rules of thumb will provide maximum visual impact and shade most of the pavement while providing pedestrians with a walking area that feels safe from the automobile.

After: Special software allows planners to alter the "Before" photo above, adding trees, sidewalks and other aesthetic touches to the roadway, transforming it into a comfortable neighborhood street. The trees reduce the perceived width of the street; their canopy forms a shaded public space. Image ©1998 Treasure Coast Regional Planning Council/Dover, Kohl and Partners, Urban Design.

"Durable trees should be used. Avoid planting trees too far apart. Most types of trees spaced over thirty feet apart will develop an open grown form branching close to the ground. This is not suitable for street trees.

"Street trees should be at least four to five inches in caliper when planted. This will help reduce damage from carelessness or vandalism. In addition, the trees will provide earlier shading and visual benefits.

"Plant only one type of tree on both sides of the street in any one block. It is best to use a tree type that has already grown successfully in your community under similar conditions. It provides for visual continuity along the street. Diversity, if desired, should be provided at the city or town scale, not within a single block or street. Diversity of tree species does not create a more robust stand of trees. In fact, on an urban site, the reverse is generally true."

Four basic building types for neighborhoods:
Single-family, fee-simple houses

Cottage

©1997 Armando Montero/Geoffrey Ferrell and Suzanne Askew—Urban Design and Landscape Architecture.

Careful urban building placement provides this detached single-family house with a comfortable, private backyard, even on a very small lot. The floor plan is carefully arranged for light and views from the street and gardens-limiting exposure to the privacy side. Sitting broad to the street, the house preserves a large and usable backyard that is separated from the street. The side-wing master bedroom, with its excellent relation to the private yard, would also be a good location for a kitchen or a family room.

The example above right is an approximately 1,400 ACSF (air-conditioned square footage) house on a 42' x 90' lot. The house sits 5' off the street frontage, 2' 6" off the alley and 3' off its privacy-side lot line. The 8' x 28' front porch is raised 30" above the sidewalk and provides a great vantage point for "watching the neighborhood go by."

While there has always been a place for large-lot houses in our towns and cities, the cottage type is the predominant form of house found in our healthy, longstanding neighborhoods.

Rowhouse

©1997 Armando Montero/Geoffrey Ferrell and Suzanne Askew—Urban Design and Landscape Architecture.

Arguably the most efficient form of urban housing, true rowhouses deliver comfortable private open space and define the street space completely. A consistent side wing gives the courtyard complete privacy from the neighbors. Deep and broad front porches provide individual definition to the units.

Floor plans should be relatively thin to allow natural light and cross ventilation. Because they have two fewer exterior walls, rowhouses can be cooled more efficiently than free-standing houses.

So long as the party walls are solid and soundproof, rowhouses can provide high quality in-town living on very small lots. On a 32' x 90' lot, this floor plan provides a three-bedroom, two-and-a-half-bath, fee-simple house suitable for a family.

Apartments, condominiums and multi-unit buildings

Small apartment house

©1998 Armando Montero/Geoffrey Ferrell and Suzanne Askew/Treasure Coast Regional Planning Council.

Small apartment houses provide an affordable and low-maintenance in-town lifestyle. These buildings sit comfortably alongside rowhouses and many detached single-family houses. Private open space takes the form of individual porches and the shared rear garden. Apartment houses should never be concentrated into an "apartment district," but be distributed through the neighborhood. They are appropriate fronting onto areas of higher activity such as the neighborhood center or main street.

This example provides two-bedroom-two-bath walk-up units, with an eat-in kitchen, plus private front and rear porches. The floor plan is arranged to allow the side windows to have high (approximately 6-ft. sill) windows—for privacy when sited next to another building.

Front elevation of conceptual small apartment house. Drawing by Armando Montero.	Floor plan for conceptual small apartment house. Drawing by Armando Montero.

Mixed-Use: shopfront

©1997 Armando Montero/Geoffrey Ferrell-Architecture and Urban Design.

Shopfront buildings, with their commercial ground floors, belong on active, well-trafficked streets. Ground-floor plans should be flexible to accommodate a variety of retail or office uses. Upper-story uses are best as residential apartments, but may be offices on very busy streets.

The specific example at right illustrates a good building type for today's new town and neighborhood main streets. The upper-floor residential units are entered from a common circulation balcony at the rear of the building. Overlooking the interior-block parking area, this access point provides good "eyes on the street"-type safety. It also allows for private balconies overlooking the street. The residence must also have an entry door on the street.

The experience-to-date in Florida's new urban and infill development is: new above-shop apartments, on real streets, have an oversupply of tenants. This way of living is not for everyone, but it has been a strong market in Florida. Above-shop residences have proven they can provide quality, affordable, in-town living.

The urban block
The urban block is the basic unit of neighborhood building. Blocks have an outside and an inside. The block defines the public space of the street with its building facades (and garden walls or fences) and holds the private realm of the houses and yards within it.

Changes in land use should be made within blocks, at the alley or rear lot line—never along streets. The changes are seamlessly absorbed at the alley. It is normal for a block to have a bustling main-street face and a quiet, residential face just around the corner. This is so normal, in fact, that we have all seen and walked by these blocks without noticing them.

It is important to place main-street buildings (more intensive uses in general) close to the main street and not overlooking less intensive uses at the rear lot line. This breathing room allows a less intensive use, such as a single-family house, to sit just around the corner from a much more intensive street (a broadway-type street, for example).

By requiring street build-to's and rear setbacks (keeping buildings close to their street), larger main-street buildings maintain a comfortable distance from side-street buildings. By keeping the interior of blocks open for trees, gardens and/or parking, rear yards are better private spaces and serve as lungs for the town.

Alleys, common drives, lanes

Block view showing alleys, common drives and lanes. Trees have been omitted for clarity. Drawing by Marcela Camblor, ©1997 Treasure Coast Regional Planning Council.

Alleys neatly accommodate the garbage, garage doors and parking lots that we have come to accept as "normal" for street fronts.

Alleys are streets, but the lowest category of street. In very urban situations—Miami Beach, for example—alleys can even have residential and commercial frontages. In less dense situations, they can have secondary units (granny flats, garages, workshops) and basketball hoops. Alleys are active places.

Like streets, alley rights of way must be delineated with fences and walls, to form a clear public space (see "Crime Prevention through Design").

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