20 Onsite and Offsite Factors You Should Consider for Site Analysis

Site planning is the art of arranging structures on a land and shaping the space in between them. Site analysis is a technique which is part of  site planning that helps us understand the various factors at play. 

What is the need for site analysis?

• To learn the strengths and weaknesses of the site.
• To understand the site and derive the form and function of the building based on the factors.
• To fix issues on the site, if any.
• To try and predict the potential future changes in or around the site and design the building accordingly.

The major site factors can be divided into onsite and offsite factors in the book 'Site Analysis' by Edward White.

Onsite factors Checklist for Site Analysis

They refer to the factors present on the site.

The major ones are-

1. Location
2. Size
3. Topography
4. Vegetation
5. Drainage
6. Groundwater
7. Soil
8. Danger signals
9. Man-made features
10. Legal factors
11. Utilities
12. Right of way
13. Circulation
14. Microclimate
15. Sensory 

Offsite factors Checklist for Site Analysis

These refer to the features around the site.

Some of them are-

1. Climate
2. Access
3. Neighborhood
4. Culture
5. Views 

Onsite factors 

1. Location

• Coordinates
• Area of the site
• Names of the adjacent road
• Landmarks
• Nearest services like hospitals, airports, schools, stores etc.

2. Size

• The length and breadth of the land should be noted.
• The total buildable area after subtracting the area for setbacks and easements should also be calculated.

3. Vegetation

• Includes the trees, shrubs and groundcover on site.
• They affect the wind pattern and drainage of the site.
• Weeds and ground cover can be removed while trees should be retained.
• The building can be designed to use them as buffer or shading devices.

4. Topography

• Refers to the features of the surface of the land.
• Contour, high points, low points, ridges, valleys and flat land should be documented.
• Flat surface is best used for intensive activities.
• Steep slopes are hard to construct and move on.
• Buildings can be constructed between 1:6 and 1:12 slope.

5. Drainage

This depends on the contour of the land.

6. Groundwater

• Refers to the water below the surface level.
• Construction should be done considering the depth of the water table.

7. Soil 

• The soil should be tested to determine its soil-bearing capacity.
• Depending on the type of soil, the foundation is chosen.

8. Danger signals are exhibited by some features like

• Rocks lying close to the surface
• High water table
• Underground stream
• Loose clay or  fine sand

They call for expert analysis and special construction.

9. Man-made features include

• Walls
• Fences
• Hydrants
• Power poles
• Pavements

10. Legal factors include 

• Ownership of land
• Setbacks- minimum open space around a building
• FSI (floor space index)- total built area/total plot area
• Height restrictions
• Allowed uses of the site

All buildings should be constructed with respect to the development control regulations.

11. Utilities

• Includes services like water, sewage, electricity, gas.
• Can be under or above ground level.
• The distance of these facilities from the site should be noted.
• Some services like HTL (high tension lines) passing through the site can make it hazardous.

12. Right of way

A part of the site can be used to provide access to another piece of land.

13. Circulation on site is of two types

• Pedestrian
• Vehicular

14. Microclimate

Apart from the general climate of the surrounding area, the site can have a microclimate determined by the following factors-

• Location of structures
• Vegetation
• Surface materials
• Topography
• Water bodies
• Surrounding buildings

15. Sensory factors are

• Visual views from the site.
• Olfactory- the smell from surrounding vegetation and buildings.
• Audible- sounds from roads and neighboring areas.
• Tactile- wind influenced by vegetation and buildings.

Offsite factors

1. Climate includes

• Rainfall
• Wind direction
• Sun path
• Humidity
• Temperature

The variations in these factors throughout the day and year and possible natural calamities like floods or tsunamis should also be considered.

The shading and ventilation of the building depends on these factors.

2. Access refers to

• The different ways of approaching the site.
• The roads around the site.
• Location of site with respect to the roads,
• Usage and traffic on these roads.

3. Neighborhood includes

• Existing buildings.
• Open spaces in the vicinity.
• Buildings with historical context.
• Vernacular context of the area.
• Possible hazardous waste disposal areas.

4. Cultural factors are

• Population density
• Age distribution
• Income and employment
• Family structures
• Crime patterns

These help in the zoning of the site.

5. Views include

• Positive and negative views.
• How the site looks from different points and how these might change with distance or time.

What is the importance of thorough site analysis?

• To have greater efficiency while designing.
• To discover the interrelationship between site factors.
• To maximize data triggers for design conceptualization.
• To avoid legal implications

Hence it becomes necessary to carefully understand and record the above-mentioned factors while analyzing the site so as to use it to the best of its abilities.