Lecture 7 Site Selection

Civil Engineering
Construction & Graphics
Site Selection Lecture # 7
Engr. Shad Muhammad

Lecturer
Department of Civil Engineering
COMSATS University Islamabad, Sahiwal Campus.
Table of Content 2
• Site Selection
• Factors affecting Orientation of the Buildings
• Factors to be considered for Site Selection
• General Precautions in Selection of Site
• Water Logging – Cases and Solutions
• The Foundation in Black Cotton Soil/Expansive
• Orientation in Different Regions
(1) Hot and Arid Region
(2) Hot and Humid Region
(3) Hilly Regions
Engr. Shad Muhammad, Lecturer, Department of Civil Engineering, COMSATS University, Sahiwal. Website: www.mytrustworth.com
Site Selection 3
• The site of a building greatly affects its planning, design and construction.
• It may be selected as required or accepted as available.
• The selection of site depends upon the purpose for which the proposed building is
to be constructed.
Building Construction – Orientation of Buildings
Factors affecting Orientation of Buildings 4
(1) Surrounding of the site
The building is to be orientated to suit the surroundings of the site.
(2) Proximity of a road or street

The building should be so orientated, as to provide easy approach from the nearby road or street.
(3) The sun
▪ The sun is a source of natural light and temperature.
▪ Sunlight is a powerful agent for killing the germs of harmful diseases like,
tuberculosis, typhoid, cholera, etc., which may, otherwise, breed in the dark and
damp corners of the building.
▪ It is, therefore, essential to orientate the building such that the sun rays may fall
sufficiently on the building and enters the building through doors and windows.
However, in summer, the building should also be protected from its severe heat.
Necessity of Natural Sun Light 6
(4) WIND
• The building should be so orientated that cool breeze enters the bedrooms during
night in summer but not in winter.
• It should also prevent direct entry of wind of heavy intensity into the building, so
as to protect the residents from dust nuisance.
(5) RAIN
• The building should be so orientated, so as to prevent entry of rain inside the
rooms.
• It should also provide minimum portion of the building subjected to direct showers
of rain, so as to prevent dampness inside the building.
Natural Ventilation Benefits 8
Building Construction – Site Selection
Factors to be considered for Site Selection 9
The selection of a building site is very important for a solar heated home or
building. Windows that face South will need to be able to have direct, solar
gain enter the windows for most of the day. You will need to inspect the
building site with a compass to determine if the Southern direction is free
of conifers (pine trees), buildings, walls, hills or anything that would block
sunlight from entering windows in the Winter.
Ground should be level or slope to the South. Ground should be free of

buildings, walls and pine trees. Deciduous trees (with leaves - falling off at
maturity) may be OK. These trees provide shade in the Summer and will
allow the sun’s rays to penetrate after the leaves fall off. Remember, some
of these trees do not drop their leaves until late in the Fall.
Use your Judgement!
Passive solar heating is accomplished by allowing the Winter sun
to heat up living space air and an internal mass which releases
heat later in the day or night. The radiant heat from the sun must be
allowed to enter through South-facing windows and be captured by
surfaces that are painted dark colors (black is best).
A floor mass is constructed of concrete, rocks and sand. These

items are inexpensive and require no moving parts. Insulation
should be placed over the windows at night so heat will not escape.
There are a variety of insulated curtains, blinds or panels that can
be placed over windows to decrease heat loss at night. The
homeowner will need to be creative to obtain and use this
insulation. This insulation is removed on the following day, to allow
the sun once again to heat up the living space and internal mass.
Overhangs or awnings can shade the South-facing
windows in the Summer. Because the sun rides lower
in the Winter, the construction of the house can allow
solar heat gain to enter the South-facing windows,
warm up the living space and heat an internal mass.
(1) Level of the site
The level of the site must be higher than that of its surroundings, so as to
provide good drainage.
(2) Climatic Conditions

The intensity of rainfall and sub-soil water level should be low, so as to avoid
dampness in the building.
Climate is the long-term average of weather, typically averaged over a period of 30 years.
A downspout, waterspout, downpipe, drain spout, roof drain pipe, leader is a pipe for carrying rainwater from a rain gutter.

Gutter: a shallow trough fixed beneath the edge of a roof for carrying off rainwater.

(3) Sub-soil Conditions
A hard stratum should be available at a
reasonable depth (3ft to 4 ft from the ground
level), so as, to construct the foundations of
the building safely and economically.
(4) Availability Of Modern Amenities

The site must be within municipal limits, so
that, modern amenities like, water supply,
electricity, sewerage, roads, etc. can be made
available with more ease, if there is no
provisions at present.
(5) Availability of other Facilities
The site should provide an easy access from the nearest road and offer sufficient
light and air. There should be good and cheap transport facilities available near the
site. It is always better, if public services like, fire brigade, police station, schools,
etc., are also not very far off from the site.
(6) Surroundings
The situation and surroundings of the site must be such as to suit the purpose for
which the building is to be constructed. Each type of building requires different
surroundings, than for others.
E.g. A house should not be constructed in industrial area.
General Precautions in Selection of Site 18
(1) The site consisting of reclaimed soil (made useful for cultivation) should be
avoided, as far as possible.
(2) The site must not be located in water logged areas or near the bank of a
river.
(3) Old quarry sites must be avoided, as far as possible.
(4) The site for a residential building should be away from the area causing foul
odor or smoke nuisance due to industrial buildings.
(5) The site for a residential building, school or hospital should be away from
noisy areas.
(6) There should be no disabling easement (Easement is a right, which a person

may have over another man's land by law, such as, the right to walk over it or to
run a pipe through it).
Orientation in Different Regions 20
• The climatic conditions, intensity of sun, and the direction of wind differ from
region to region. It is, therefore, not possible to follow a rigid method, with
regard to the orientation of buildings.
• In general, the Earth's surface is divided into three different regions with
respect to the orientation of the buildings. In these regions, the orientation is
discussed separately.
• In these regions, the climate is extreme; the temperature ranges from 50C0 maximum to
36C0 minimum, or, more or less.
• Cloudless sky, low humidity, and high incidence of Sun's glare are the main features.
• The sunny areas are hot and dry in the day time and cool to cold at night.
• As far as possible, the building should be protected from day time heat and glare during
summer and at the same time, the rate of heat loss at night during winter should be
reduced.
• In these regions the building should be oriented for the Sun, not for wind as in humid
regions.
The following points should be kept in mind while orientating building in such areas:
• To minimize the heat gain during summer and take benefit for solar heat during winter, the
longer walls should face north and south and shorter walls, east and west, so the least wall
area is exposed to the slanting rays of Sun during fore noon and afternoon.
• In other words, we can say that the longer axis of building should run east west, so as to avoid
excessive heat from west side.
• Provision of projections on the southern walls will give sufficient shade to the
walls during summer and provision of windows and openings on the southern wall
will allow sunrays to enter into rooms during winter, because the Sun's altitude is
high in summers and low in winters.
• Verandahs are desired on the south for protection from heat in summers and,
also, for sitting out purposes in winter to enjoy the Sun's heat.
• Openings in the west should be small and should
be properly orientated. (To save the cost of
verandah on the west, the afternoon's Sun may be
kept off by providing Louvers, which are
ventilators, sometimes provided in windows also,
in which horizontal sloping slats allow ventilation
but exclude rain and Sun's rays.)
• A small tilt in the axis of the building

must be given away from the west
towards the south (facing near about
north-west), to get maximum benefit
of breeze during rainy season,
autumn, and spring to ensure comfort
and proper ventilation.
• In this region the climate is humid, temperature in summer is moderately high and
rainfall is heavy.
• The prime object for orientation and design of buildings in this region is to provide
free air movement through the building and to prevent the temperature rise of its
inside surface above the shade temperature.
The following aspects should be considered while designing buildings in these areas:
• The building should face the direction of the prevailing wind to obtain maximum
benefit of the air movement.
• A tilt, up to 45 degree may be allowed, if required, for which the loss of

efficiency is only up to 20%.
• Window sills should be low to ensure maximum ventilation at the normal living
level.
• Walls should be shaded from the sun, so as to prevent the temperature rise.
• Protection of openings against rain is also necessary.
• Building should normally have open planning, as far as possible. They should be of
one room thickness, so as to ensure thorough ventilation.
(3) Hilly Regions
• In these regions, temperature is usually much low and cold dominates according to
the increasing altitude.
• There is marked drop in the temperature during night.
(3) Hilly Regions
The following points should be kept in mind while orientating building in such areas:
(1) The buildings should be located in the southern slope of the hill, as they
receive maximum sunshine for the greatest duration of time.
(2) The opening should be placed as to allow sunshine inside the building.
(3) Hilly Regions
(3) A massive structure with high heat capacity is useful because the heat, it stores during
the day is welcome, except in very hot day.
(4) It is necessary to provide ceilings of good thermal insulation to reduce loss of heat by
radiation during night.
(5) In areas, with heavy snowfall, the roof should be kept sloping to prevent accumulation
of snow.
Which Problems Occur due to the Water Logging?
Following problems will occur due to the water logging in foundation pit:
1. Difficult to further excavate further deep

2. Difficult to remove excavated earth
3. Collapse of earth from the sides of pit
4. Excess and continuous water will increase w/c ratio and will make concrete weaker or even useless
5. Difficult to work
6. Mud will enter, pit, mortar or concrete
7. Safety of worker
Water Logging – Case # 1 34
(a) When Surface Water is Encountered
• Surface water is not the major issue. Surface water logging can be easily drained
out by providing a marginal slope to the ground. Filling of the good soil at the
uneven surface can be helpful to overcome the problem of water logging
• Remember that water should be drained out before filling the good soil at the
site.
Water Logging – Case # 2 35
(b) When Ground Water is Encountered
• If the water table falls within the depth of excavation, the depth of the foundation may
be decreased up to the top level of water table, and the size of foundation should be
increased.
• But minimum depth of foundation should be provided or foundation should be rested on

good soil. By doing this you can avoid water logging. It is must to contact a well
experienced structural engineer to check the feasibility of this kind of foundation design
in such a waterlogged area.
Water Logging - Solutions 36
• In the waterlogged area or where water is encountered, the foundation work should be
carried out in a very systematic manner. Foundation should be excavated one by one
otherwise you will have to face this problem.
• Provide sufficient slope at bottom of foundation pit so water can be directed towards the
sump which can be located at the corner.
• Remove water from the sump by deputing labors. You might have use mud pump
continuously to drained out the water.
• Finish the RCC work of one foundation and then start the excavation of next foundation.
• If you start the excavation on the whole site, you mess up the whole area due to the
water logging and you have to deploy the extra labors to do the activities like mud
cleaning, frequent repairing of the muddy road, removing collapsed soil/mud, etc.
• The higher working space should be considered while excavating the foundation
pit. Higher working space will facilitate you to construct the sump and drain at
the bottom periphery of the foundation. The drains collect the excess water of
excavated pit and transfer it to the sump, from where water is drained out
manually or by means mechanical pump (mud pump, anti-clogging pump).
• Suppose you have to excavate up to 7 feet and water table is at 6 feet. On first
day excavate up to 5 feet only so that water does not enter. Next day excavate 2
feet, do sand filling/PCC and also do footing. Keep everything ready for doing
that fast. Idea is to complete the work fast, so that water does not accumulate in
large quantity. If needed run pump all throughout work. Repeat this process one
by one for each footing.
• Add lime in the bottom 1’ 0” of muddy soil, rather than excavating it and when it
is difficult. Stabilization of soil with 2 to 5 % of lime will help to stabilize the soil
and reduce the entry of water. You can also use cement, fly ash, aggregates, etc.
to overcome the problem of water logging. In the case of higher water pressure,
the soil stabilization will not be effective and suitable.
• Sometimes sand is also sprayed over the muddy surface in the layer of 100 to 200
mm thickness. Sand layer filters the mud and allows clean water to enter in the
pit without higher flow. This provides mud free platform to work in the foundation
pit. We very well know that working in fresh water is far better than working in
the muddy soil. You can do immediate PCC over it. By doing these 2 layer, you will
automatically come 150 to 200 mm above where water may perhaps not come.
Sand Sprayed Over the Muddy Surface
• In case of groundwater with high flow,
make a layer of PCC 1:3:6 or sand 250
to 300 mm.
• There are different methods of
dewatering that are used to remove
the water from the water-logged area.
We have already discussed the
different types of dewatering methods
and their use in construction.
Generally, these methods are
expensive for small work.
• Constructing a foundation in a
waterlogged area becomes hassle free
when you know the aforementioned
tips.
• Generally, water is not a big problem,
it is the mud that bothers everyone.
Water can be easily drained out with
the pump but the mud causes lots of
trouble. Sometimes even mud pump
also fails to drain out the muddy water
from the waterlogged area.
The Foundation in Black Cotton Soil/Expansive 42
• Alternate wetting and drying of the soil is not the
favorable condition to rest the foundation. i.e.
Generally, the water table is high during monsoon, and
it gets lowered during the dry season which causes the
uneven settlement of soil. This uneven settlement of
soil badly affects the structure.
• In such case, rest your foundation at the depth where
the soil is either completely dry or completely wet,
so that it is safe from alternate wetting and drying. So,
decide your level and foundation accordingly.
Thank-you for Listening! 43
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(Shad)

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Civil Engineering

Construction & Graphics

Site Selection Lecture # 7

Engr. Shad Muhammad

(2) Hot and Humid Region

(3) Hilly Regions

• It may be selected as required or accepted as available.

(2) Proximity of a road or street

Ground should be level or slope to the South. Ground should be free of

A floor mass is constructed of concrete, rocks and sand. These

(2) Climatic Conditions

Building Construction – Site Selection

Building Construction – Site Selection

(4) Availability Of Modern Amenities

(3) Old quarry sites must be avoided, as far as possible.

(6) There should be no disabling easement (Easement is a right, which a person

• A small tilt in the axis of the building

• A tilt, up to 45 degree may be allowed, if required, for which the loss of

• Protection of openings against rain is also necessary.

• There is marked drop in the temperature during night.

1. Difficult to further excavate further deep

(a) When Surface Water is Encountered

(b) When Ground Water is Encountered

• But minimum depth of foundation should be provided or foundation should be rested on

Sand Sprayed Over the Muddy Surface

To become valuable, start delivering your services above your salary!

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