Building Planning & Foundations

Principles of building planning

Site selection for a residential building

• Good locality — pleasant surroundings, security, neighbourhood facilities (schools, hospitals, markets, transport).
• Level, well-drained land above flood level; not low-lying or filled-up ground.
• Good soil with adequate bearing capacity; low water table.
• Access to roads and availability of services — water supply, sewerage, electricity, telecommunication.
• Open surroundings — good light, ventilation and view; away from noise, smoke and industrial pollution.
• Legal aspects — clear title, permitted land use under the master plan, bye-laws.
• Cost of land and development.

Orientation of buildings

Orientation is the placement of the building with respect to the sun path and prevailing winds to achieve thermal comfort, natural lighting and ventilation.

Sun and heat

• In India (northern hemisphere, tropical to sub-tropical latitudes), the sun is mostly in the southern sky, rising in the east and setting in the west.
• East and west walls receive intense low-angle morning and afternoon sun that is difficult to shade — so longer walls are preferably oriented to face north and south, with the shorter walls facing east and west.
• South-facing openings can be shaded effectively by horizontal overhangs (chajjas) in summer while admitting low winter sun; north light is diffuse and glare-free (studios, workshops).
• Service areas (stairs, toilets, stores) can be placed on the west as buffer zones in hot climates.

Wind and ventilation

• Openings placed to catch the prevailing breeze (in many parts of India, south-westerly winds in summer and monsoon), with inlets on the windward side and outlets on the leeward side (cross-ventilation); outlet area preferably equal to or greater than inlet area.
• Building oriented within about 30–45° of the wind direction still achieves good cross-ventilation.

Shading devices

Horizontal devices (chajjas, overhangs) — effective for south openings; vertical devices (fins) — effective for east and west when combined with horizontal elements (egg-crate); louvers, jaalis, verandahs, trees and pergolas.

Climatic zones of India (for building design)

Functional planning of residential buildings

• Zoning — living zone (drawing, dining, verandah), sleeping zone (bedrooms, dressing, toilets) and service zone (kitchen, store, utility, washing, toilets) — with appropriate relationships and privacy.
• Room relationships — entrance → living → dining → kitchen; bedrooms with attached or nearby toilets; kitchen near the back entrance/utility.
• Circulation — minimise corridor areas while providing independent access.
• Services — plumbing grouped (kitchen and toilets vertically aligned in multi-storey buildings), electrical layout, drainage.
• Types of residential buildings — detached, semi-detached, row (terraced) houses, flats/apartments (walk-up and high-rise).

Building bye-laws and regulations

Building bye-laws are rules framed by local authorities (municipal corporations, development authorities) to regulate building construction for health, safety, convenience and orderly urban development.

Objectives

• Ensure structural safety and fire safety.
• Provide adequate light, ventilation and sanitation.
• Prevent overcrowding and haphazard development; protect neighbours' rights to light and air.
• Maintain the planned character of areas (land use, density, heights).
• Provide parking, access and services; accessibility for persons with disabilities.

National references include the National Building Code of India (SP 7), BIS codes, the Model Building Bye-Laws (MBBL, 2016) issued by the Town and Country Planning Organisation, and state or city-specific bye-laws (e.g. unified bye-laws of large cities). Actual values vary by authority and are revised periodically.

Typical controls

Requirements of a foundation

A foundation must:

1. be safe against shear failure of the soil (adequate bearing capacity with a factor of safety);
2. keep total and differential settlement within permissible limits;
3. be placed at a depth safe from seasonal moisture changes, frost, scour and the effect of adjacent construction;
4. be structurally strong and durable against aggressive soil and water;
5. be economical and practical to construct.

Types of shallow foundations

Depth of foundation

Factors governing depth

• Stratum of adequate bearing capacity and acceptable settlement.
• Seasonal volume change zone in expansive clays (often 1.5–3.5 m in black cotton soils).
• Frost penetration in cold regions.
• Scour depth for bridge foundations near water.
• Ground water level, adjacent foundations and future excavations.
• A minimum depth of about 0.5 m (practice often uses 0.8–1.0 m for buildings) to remove topsoil and vegetation and protect against weathering.

Rankine's minimum depth (cohesionless soil)

For a footing with pressure $q$ on soil with $\gamma$, $\varphi$:

Proportioning footings for uniform settlement

Footings of different sizes carrying the same pressure settle differently (larger footings settle more on clay because the pressure bulb is deeper). To reduce differential settlement, footings may be proportioned on the basis of the dead load plus the average (sustained) part of the live load rather than the full design load: the footing with the highest ratio of live to dead load is sized for the allowable pressure under full load, and the same "service" pressure is used for all others.

Combined footings

For two columns with loads $P_1$ (exterior, at property line) and $P_2$, spaced $s$ apart:

1. Locate the resultant: $\bar{x}=\frac{P_{2}s}{P_1+P_2}$ from column 1.
2. Make the centroid of the footing coincide with the resultant so pressure is uniform.
3. Rectangular footing: length $L=2\times$ (distance from property line to resultant); width $B=\frac{P_1+P_2}{q_{a}L}$.
4. If the length is restricted at both ends or loads are very unequal, use a trapezoidal footing (wider under the heavier load).
5. Design longitudinally as an inverted beam (upward soil pressure, columns as supports) and transversely for local bending under each column.