3. RESIDENTIAL DEVELOPMENT

3.1 Development Criteria

Residential development dominates the built landscape. This form of development represents the most predominant land use in both urban and rural settlements. As the primary base for living, social interaction, and recreation, the residential environment has an important influence on the quality of life. The scale of residential development could also present implications for safeguarding the natural environment. Uncontrolled and indiscriminate residential development could lead to such problems as soil erosion, flooding, and waste pollution. The planning and development of large scale residential projects therefore require professional planning and engineering expertise.

The primary concerns regarding residential development are therefore to satisfy certain basic human needs and to minimise any possible adverse impacts on the environment. Specific performance criteria may be outlined as follows:

• Positive community identity and image.
• Privacy from visual and aural contact with other activities and people as required.
• Opportunities for social contact and interaction, subject to requirements for privacy.
• Clear and organised spatial patterns and aesthetically stimulating environments.
• Availability of amenities, including natural features and community facilities.
• Safe and convenient access to amenities, public transport, and employment sites.
• Safe and comfortable environments providing a sense of physical and social well-being.
• Maintenance of the integrity of key features and processes of the natural environment.
• Protection from environmental hazards (natural, man induced).
Adequate infrastructure systems (water supply, sewage disposal, drainage, etc.).
• Cost effective development and efficient use of land.

3.2 Density and Housing Forms

Table 3.1gives an indication of the more common types of housing that can be achieved at various density ranges. The information is intended as a guide and it is to be particularly noted that lower density housing forms or a mix of house forms could be considered for each density range specified in the Table. Innovative housing forms will also be encouraged even if this would mean slight adjustment of the density ranges. It is to be noted however that at a site specific level the specified densities might be affected by shape and topography of the site. 

A range of densities and innovative house forms should be employed in large scale developments in order to provide flexibility and choice of housing.

3.3 Community Structure

Residential developments vary in scale from the one lot addition to existing built-up areas to large scale neighbourhood or community projects. Essentially however, the key components of most residential developments include:

• A range of housing densities and house forms
• A range of supporting community facilities including shopping, community centre, and schools
• A recreational open space system
• Employment sites
• Road and pedestrian circulation systems
• Utility systems.

Basic guidelines for structuring residential developments are as follows:

1. Prior to formulating proposals for the development of any site, the characteristics of the site and its surroundings should be analysed to identify development opportunities and constraints, including:
• Steep lands unsuitable for development.
• Significant views and vistas from the site to features of interest.
• Flood prone areas and wetlands.
• Unique and interesting vegetation worthy of conservation.
• Availability of basic infrastructure facilities in the vicinity of the site.
• Availability of shopping facilities, schools, and other community facilities.
  
2. Where a range of housing densities is proposed for a development, the higher density housing should be located close to the core of commercial, social, and recreational facilities and to public transportation in order to ensure the highest level of accessibility for the largest number of people.
   
3. The commercial core of a development as well as other high-level community facilities (secondary school, etc.) should preferably be located at the main gateway to the development and close to public transport facilities.
   
4. Nursery and primary schools should be strategically located within a development for safe and convenient access by their service populations. Children should not have to cross any major public roads on their journey to and from school. The location of schools close to other community facilities such as parks and community centres is also desirable.
   
5. Recreational open space should be planned as a linked system of such facilities as parks, playfields, playgrounds, riverside parks, buffers, and pathways. Parks and playfields could be associated with other community facilities such as schools and community centres. The planning of the open space system should also facilitate pedestrian movement to other community facilities provided that adequate provision is made for safety and security.
   
6. Employment sites would best be located with easy access to the external road system, downwind of the housing, and buffered from residences and schools by open space and other nonresidential uses.
7. The road system should comprise a hierarchy of residential streets designed to facilitate clear, safe, and efficient access but to discourage through traffic. To discourage through traffic, short loop streets and cul-de-sacs should predominate.
   
8. Pedestrian circulation systems should provide safe, convenient, and pleasant access within residential developments. The systems could be associated with the road and open space systems and linked to community facilities such as schools, community centre, and shopping centre.
   
9. Utility systems should provide efficient levels of service to the community without affecting the health and safety of residents or the amenity value of the environment.

3.4 Layout and Subdivision

3.4.1   Development Concepts

To a large extent the design of residential developments are influenced by certain road layout patterns, as illustrated in the following development concepts (Figure 3.1):

The Grid System:

This type of layout results in equally spaced, parallel streets with junctions at right angles to each other.  This concept could be quite efficient on flat or gently rolling land.

Present practice however discourages the strict application of the traditional grid pattern as this type of layout results in a multiplicity of cross intersections and tends to encourage the use of local roads by through-traffic. It also ignores contours and natural site features and can result in very steep roads on sloping land.  When used the grid should be adapted to respond to topography through bending and curving of streets and varying the size of blocks to create more interesting, efficient, and functional systems.

The Radial System:

In this type of layout traffic flows are concentrated in a radial pattern on centres with high levels of activity.  These centres are not easily adaptable to change and therefore the flexibility of this system is very limited.  The concentration of movement at the centre generally results in overcrowding, traffic congestion, and excessive pressure on infrastructure.

The Curvilinear System:

The use of this approach to road layout results in a pattern which is more sensitive to topography than the grid since its inherent flexibility allows each site to be designed differently within the general concept.  The use of the curvilinear system allows for more interesting streets with varied views and street types and lengths.

Limited Access Concept:

This approach is a modification of the curvilinear system in which cul-de-sacs, T-junctions, and loop streets are common features utilised to restrict through traffic and increase safety.  The concept is probably the most desirable form of subdivision layout since it recognizes site features, safety, economy, and social structure.

This approach usually results in the clustering of houses and generous open space provisions. It is extremely successful with large sites and can also be applied to small areas.

3.4.2   Plot Layout

Basic guidelines for the layout of plots in residential subdivisions are as follows:

1. Plot arrangements (size, shape, dimensions, orientation) should be sensitive to topography, micro-climate, road patterns and the building types proposed.
   
2. Plots should be laid out so that full advantage may be taken of topography. On sloping land, plots should be laid out so as to minimise the destruction of the physical environment as a result of extensive cutting, filling, and grading.  Plots on steep slopes should in general be larger than normal since portions of the site may be unusable as a result of topography.
   
3. Plots must be provided with at least one frontage having access to a street. The creation of double frontage plots and/or long narrow plots should be minimized. Where two or more road frontages exist on a single plot, the plot must be larger than normal to provide adequate space for building setbacks and home-owner privacy.
   
4. Plot lines should be perpendicular with the line of streets so that irregular or triangular shaped plots with limited possibilities for building design and/or orientation are not created.  Where the creation of irregular shaped plots is unavoidable, such plots should be larger than normal since their shape may render a portion of the site unusable for building.
   
5. On corner plots, no fence, wall, or other structure more than 1 metre in height, should generally be erected or placed within the triangular area formed by the intersection of street lines at a point 15 metres or 7.5m distance from the intersection of major roads or minor roads respectively, as measured along both frontages of the plot.  Fences above 1 m in height of an approved design which would not impede vision may be permitted e.g. iron palings.
   
6. Residential plots should not front onto arterials carrying heavy traffic.  Where this is unavoidable, such plots should have greater depth in order to provide for homeowner privacy and to minimise any noise, dust, and fumes generated by traffic.  In addition, the use of a buffer strip of vegetation between houses and the major road is recommended.

Figures 3.2 to 3.6 provide illustrations of plot layouts and design.

FIGURE 3.1
PLANNED RESIDENTIAL DEVELOPMENT
Diamond Vale, Diego Martin
Trinidad & Tobago

FIGURE 3.2
SUBDIVISION STREET PATTERNS

FIGURE 3.3
PLOT LAYOUT

FIGURE 3.4
TYPE OF PLOTS

FIGURE 3.5
PLOT DESIGN

FIGURE 3.6
BUILDING LINE ON CORNER PLOT

3.4.3     Minimum Plot Size and Dimensions

The minimum size of plot which will be permitted in subdivision layouts generally varies with:

• The intensity of development which is desired for the site and surrounding areas.
• The physical characteristics of the land to be subdivided including the natural slope of the land.
• The general character of the surrounding area within which the land is located.
• The capacity of existing infrastructure facilities in the area.

Plot dimension standards are expressed as a ratio of plot width to plot length (Figure 3.7).  In new subdivisions, the ratio of plot width to length should not exceed 2 to 5 i.e. the width of the plot should not be less than 40% of the length.  The standard width for plots should not be less than 15 metres.

Within the constraints of minimum plot size and dimensions standards, variety in the size and shape of subdivision plots is encouraged.