COST EFFECTIVE BUILDINGS- A new approach
Er.
Suresh Lal. S.D
Consultant, CivilTalents Technical Consultancy Services, Kochi
There was a trend from the early days to
reduce the cost by saving the unwanted expenses occurred during construction of
any structures meant for residential as well as commercial purposes. Alternate
construction materials and new methods of construction were adopted to reduce
the cost optimum. More over a lot of research was done in this field to bring
out the means to reduce cost of construction. Using these methods the
construction works were carried
economically. Since the cost of
such buildings were ‘low’ compared to the existing conventional buildings, the name of “Low Cost
Houses’ evolved.
On the other
hand now a days a new term is
substituting the ‘Low Cost Houses’ ie.
Cost Effective
Buildings. Perhaps this may be the apt word for this due to the following
reasons.
- For a particular model or type of
construction it is not possible to reduce the cost. Only the cost
effective techniques are adopted for reducing the cost. For each and every
type of construction, the cost varies accordingly and we cannot tell a
construction as low cost.
- Instead of Low cost technologies, cost
effective technologies are much more adaptable to the same concept and
practices.
- This shall be a modified version
of the so called Low cost houses rectifying some of the defects developed
or observed during the past decades.
The evolution of
the cost effective buildings opened a new era in the construction industry in the late 70’s. A lot
of new construction methods were adopted against the conventional practices
existed at that time. Due to those methods the owner was able to reduce the
cost up to 30%. He could make more eco friendly houses.
In Kerala, such
a practice of constructing houses at low cost is not obtaining popularity in
the recent years as it got in the 80’s. The various low cost technologies
adopted were done with a vision to reduce the cost only. For explaining this,
the psychology of Keralites has to be considered. We Keralites believe our
houses as a prime social status symbol. More over we people consider their
houses as a good way of investment. They don’t feel bad in selling the house
and buying a new one. So the construction goes normally to a standard quality
work with costly materials.
Most of us
normally says, ’this building should get a good price if sold on urgent in need
of money’. We know that if the building
is labelled as ‘Low cost building’, then on selling the property what we get
will also ‘low’. So most of the people are afraid to admit to construct the
their houses in a low cost manner. On the other side most of them suffer very
much due to their financial burden occurred due to construction and forced to
relocate their habitat after selling the
newly constructed ones. Recently making and selling the houses increased
manifolds to recover the property from heavy and increasing debts.
The below mentioned factors should change
in order to have a healthy and positive approach towards Cost Effective Buildings from all.
Ø
Attitude
Ø
Approach
Ø
Concept
Ø
Knowledge
Ø
Comparison
with others
Ø
Vested
Interests
Ø
Profit
Motives
Ø
Over
Design as in Government works
The advantages of low cost/ cost effective
buildings are as follows:
1) It saves money: Upto 30% of the
conventional cost can be saved if strictly following all the construction
techniques. Whatever amount invested above the minimum requirement shall be
considered as a wastage. Such a huge amount is becoming a dead investment in
the whole construction industry of our country day by day. If we can redirect
this amount for social development, this could
do wonders in the economic field of our Nation.
2) Cost effective construction
methods normally use low energy and low energy products. This makes a prominent
role in saving the controlled usage of the energy. Eg: Lime and its products
consume less energy while cement and its products consume more energy. The
terracotta tiles consume comparatively less amount of energy while the modern
ceramic and other vitrified products consume more energy.
3) Cost effective technologies uses the human
labour resources in an economic level. By limiting the construction processes,
a considerable wastage of labour forces and other technical resources are
avoided.
4) The environment friendly
materials and some most common and locally available materials are used in this
type of construction. This will keep the equilibrium of each places and the massive dislocation of
the construction materials is prevented. Thus fossil energy such as petrol and
diesel is saved to a large extend in the form of transportation from one place
to another.
5) Aesthetic look of the low cost buildings are
elegant compared to that of the conventional multi colour painted and
complicated structures.
Cost effective buildings go along
with the concepts and dreams of the ideal house for every one. Some other facts which was mentioned earlier
divert the owners mind to conventional high cost construction.
| Part of the | % of costof | % saving under CEC | % of total saving | ||
| Building | eachpart | min | max | min | max |
| Foundation | 10 | 0 | 0.5 | 0 | 0.05 |
| Super structure | 17 | 20 | 33 | 3.4 | 5.61 |
| Doors & Windows | 17 | 10 | 45 | 1.7 | 7.65 |
| Roofing | 26 | 10 | 35 | 2.6 | 9.1 |
| Plastering | 8 | 30 | 85 | 2.4 | 6.8 |
| Flooring | 5 | 10 | 40 | 0.5 | 2 |
| Plumbing, sanitary& | |||||
| Electrification works | 17 | 0 | 10 | 0 | 1.7 |
| Total | 100 | 10.6 | 32.91 |
Cost Effective Construction methods adopted
The cost effective construction
methods put the supervisory staff and the consultant in pressure to execute
good quality work. Without proper supervision, a chance of poor workmanship
occurs and this will destroy the quality and durability of the structure
constructed. Since utmost care is taken at all stages of the work to ensure the
quality of construction.
Foundation and basement: In this
category the savings are comparatively less compared to other parts of the
building. Foundation is the most important part of the building and the work
has to be completed as per the decisions of the Consulting Engineer.
During
the Rubble work extreme care has to be taken to ensure there is good bonding in
the Random Rubble (RR Masonry). The rubble work can be done in good quality mud
mortar also. 1 part of lime with 3 parts of sand and 8 parts of red soil mixed with water in good consistency
make good quality mortar for rubble work.
Try to
reduce the offsets in the Rubble work as much a possible. In small residential
buildings, foundation and basement can be made as a single piece without
leveling and offsetting at the top of the foundation.
In the clayey soft soil, there is an alternate solution for small
houses. If the Rubble cost is more or the transportation is very expensive,
bamboo reinforced mud work is strong enough to carry the load. Strong and
durable arecanut slices can also be used in the place of bamboo.
Wall: We can make considerable amount of
savings in wall construction. In the conventional style of construction,
English bond and Flemish bond are used to get a truly solid brick wall with 9”
thickness. Here the mortar consumption is more.
In Cost Effective Construction methods
the following type of wall construction methods are mentioned and each of them
will be explained in detail by listing the advantages and disadvantages of all.
a)
Rat Trap bond
b)
19 cm thick modified
brick work
c)
Hollow Concrete Blocks
d)
Pre cast Stone Masonry
Blocks or Random Rubble Masonry Blocks
e)
Interlocking stabilized
mud blocks
f)
Stabilized Earth Blocks
Each item is
explained here specifying the Advantages and disadvantages
a)
Rat Trap Bond:
In rat trap bond, merely the laying of the bricks differ in tits
style compared to that in conventional work. In conventional style of brick
work, bricks are placed with it 4.5inch side horizontal over the wall. But in
Rat Trap Bond, this side is kept vertical creating a void space in between the
two outer bricks. Alternate layers are placed in such way that there is no vertical joints
continuously. Fig1.
Advantages of Rat
Trap Bond
1.
Upto 25% savings in bricks and
mortar altogether.
2.
Air gap inside the wall
prevents penetration of heat through walls. Practically we feel more comfort
living inside these type of buildings.
3.
The inner bricks normally
remain damp proof in rainy season.
4.
It provides a pleasing
Aesthetics after a good pointing.
5.
Irregular shaped bricks can be
used effectively in this type of wall construction.
Disadvantages of Rat Trap Bond
1.
Strength is less compared to
the solid walls of same thickness.
2.
Since there are voids in the
walls, there may be trouble of rodents or other small creatures may take
shelter inside.
3.
Hollow spaces are continuous.
Labour cost is more, since the
careful laying of each brick consumes more time. The mortar joints are
comparatively less. So inserting mortar needs more attention
a)
19 cm Thick brick wall
This is
an alternate method to the conventional 23 cm thick brick wall. It consists of three bricks laid flat on one
face with two bricks laid on the edge at the other face. The faces with flat
bricks and the bricks on edges
alternated after every 23 cm. 17.5%
savings is obtained through this method. The bricks placed on its edges prevent
intrusion of dampness to the inside of the walls. Since horizontal joints are
not continuous, it prevents the entry of dampness also.
Advantages
of 19 cm thick wall
1.
The wall is solid and strong.
2.
The dampness entry is
restricted during rainy seasons.
3.
Pointing or plastering may be
done for the walls.
4.
Pleasing Aesthetics is
obtained.
Disadvantages
of 19cm thick wall
1.
Since there is no header
bricks, strength is less.
2.
Sometimes the unpolished
surface of 4.5” flat side may be seen outside in case of pointed walls.
3.
Less load carrying capacity
compared to the conventional type of brick work.
b)
Hollow Concrete Blocks
(HCB)
None of
the Cost effective building practitioners have given much attention in this
field. But the common man have approved this material as a very effective cost
reducing material.
The
entire making of the block and the raw materials are highly energy consuming.
These blocks are available in various sizes. The cost of one block is less compared to the number
of bricks used in its place. The daily or weekly fluctuating price of cement is
not helpful in assessing the percentage of profit. Solid blocks can also be
made with the same machinery for making the outer walls.
This is
used extensively in the Middle East (Gulf countries) as a non-load bearing
partition wall construction. Since our workers have got NRI connections and
work experience in those countries, everyone has got a good an attachment with
HCB. You can very easily pick some good
workers for HCB work rather than for brick work or laterite work.
Advantages if HCB’s
1.
Manufacturing of HCB’s are very easy with hydraulic or
electrically operated machines.
2.
Different sizes of blocks are produced with
the help of different moulds.
3.
Uniform size and regular outer
surfaces help in neat look and good savings in the plastering.
4.
Since there is hollow space
inside, the weight is less and very easily handled.
5.
The hollow spaces are unit
based and not continuous.
6.
Can be produced in the site
with a small machinery assembly.
Disadvantages
if HCB’s
1.
High energy required for the
entire process of manufacture.
2.
The solid blocks are too heavy.
3.
Cutting half blocks are difficult either produced in
required size in advance.
4.
Suitable for non-load bearing
walls of the framed structures (structures on columns and beams)
5.
Cost of the raw materials are
fluctuating. Especially the cost of
cement.
6.
Proper curing is required for
good quality product.
7.
Dampness enters the room is the
our side is wet.
a)
Random Rubble Masonry Blocks
This also called Precast Stone Masonry Blocks. This has got immense scope in Kerala where at
all places large deposit of different types of stones is available. A lean
concrete mix of 1:5:8 (1 cement : 5 sand or graded quarry dust : 8 parts 12 mm or 20mm metal) is poured in a mould and different size
stones are placed in it and filled with concrete mix. These stones can utilize
maximum volume of the block by skillfully packing the same. A plate vibrator is
used to vibrate the block to get maximum strength. The stone pieces laid shall
keep a minimum distance such as the concrete shall fill and bind the stones.
Waste and unused stone pieces are collected and battery type mould
can be used. After filling and proper vibration, that shall be undisturbed for
24 hours and then stacked on wet ground (max 6 layers).
The half and quarter size bricks has to be produced initially
because cutting and resizing of the blocks are not easy.
The main
features of the Random Rubble Masonry Blocks are as follows:
• Cheap concrete + local stones
• Moulded in different shapes
• Cement is less required
• No need of plastering
• Can be used in load bearing walls
• Less expensive than a Hollow block
• Cost Rs.5 – 10/ piece
• More strong than a I class bricks
e) Interlocking Stabilized Mud Blocks
These type of blocks can be very easily made in Kerala since we have
a good quality laterite grade soil. This soil gives good colour to the product.
This is the only type of building blocks, which require no binding mortar. The
tongue and groove type joint in all the 3 dimensions helps the bonding so
strong and rigid. There is another advantage ie. If we want to demolish and
reconstruct the same building somewhere else, it is very easy with a minimum
loss and expenses. The bricks are available in different sizes. 25x20x15 cm,
25x 15x 12 cm etc.
Advantages
of interlocking stabilized Earth blocks
•3-4 %
stabilizers & cement used
•Pressed
with machines manually or with machines
•Locally
available soil can be used
•Can be
produced in the site
•Aesthetically
very pleasing
Disadvantages
of interlocking stabilized Earth blocks
•Sometimes one has to plastered to avoid the
trouble from ants and other
small creatures which can shelter in the
small crevices.
•Continuous wetness will develop algae growth
on the surface utilizing biomass from the soil.
•The blocks are very heavy compared to HCB or
other blocks since it is compacted well and no voids present.
a) Compressed Earth Blocks (CEB)
Earth shelters can be improved by enhancing
the properties of the wall. Ordinary raw earth blocks are used extensively in
the buildings in all over India. The main drawbacks of these raw blocks are:
1)
Limited load bearing capacity
2)
High water absorption
3)
More time required to dry
These drawbacks are solved in
Compressed Earth Block. By compaction with 10 tons pressure, under very low
water content, we get very high quality blocks with a small amount of
stabilizers such as cement or lime.
23cm x 10.8 cm x 7.5 cm and 23 x 23 x 7.50 cm are two normal sizes of the
pructs made.
Advantages:
1. This product can be produced in
the site itself.
2. Cost is very less
3. Hand operated machines such
as TARA Balram machines can be used to
produce blocks.
4. Very fast setting of the blocks.
5. No separate curing method is to be
adopted.
6. Aesthetically pleasing
Disadvantages
1. Bricks are too heavy
2. These are brittle
3. The quality of the soil used is
the important factor as far the strength of the product is concerned.
Other
Components in Walls
In
constructing walls, there are some other construction factors which influence
the cost of the building. They are
a) Doors and windows
b) Lintels and Lintel Beams
c) Other projected slabs on the walls
In
the making and fixing of doors and windows play an important role in the
construction estimate of the Project. Normally 17% of the total cost is
incurred on moderately wood-used buildings. The maximum percentage shall be 20%
depending upon the type of the building.
But
this amount can be reduced considerably with the help of new construction
materials and by limiting the usage of wood. The main alternative of wood is
Iron. Aluminium can also be used, but cost is a main factor, which prevents us
from using Aluminum other than for some specialized uses.
Even
though we admit that there is no other material can substitute the wood, we are
forced to find out other alternatives
due to day by day increasing cost of wood and to protect the environment
by reducing the destruction of trees.
Welded
steel frames can be used with hinges welded to it with the frame. Low quality
wooden planks or block boards can be inserted in the steel frame shutter. This
can be even simplified with a single shutter rotating in a pivot and without
any frames. The walls can be made such that it works as a door frame.
The
window frames can be completely fabricated in steel ‘Z’ angles and ‘L’ Angles.
Square bars or round bars are provided as window bars as in wooden windows. The
window shutters are also welded in hinges to the frame so that additional cost
in fixing the window shutter can be avoided. Now a day this sort of windows are
approved by Government Agencies and Departments, which gave a good popularity
to the fabricated windows.
Advantages
1. Since the cost of wood increases
day by day and its availability decreases, steel is an effective alternative
for it.
2. For a safer environmet, the usage
of wood has to be reduced.
3. Due to environmental changes, the
warping or bending of wood is common, especially in window shutters.
4. Saves upto 50% in the cost, which
is 7 –8 % of the total construction
cost.
5. Since the thickness of frame is
less compared to wood, it gives more light and air.
Disadvantages
1. Since these are made up of steel,
it is liable to corrode.
2. periodical cleaning and repainting
is necessary to keep it durable and strong.
2) Lintels and Lintel Beams
Lintels and lintel beams are necessary
wherever it requires in a building. For this shuttering work is necessary.
Normally considerable amount of concrete and steel is required for this. Cost
can be reduced either by minimizing the concrete used or by avoiding the
shuttering work.
This is possible by replacing the lintels by
Brick arches or by concealed concreting over flat brick lintels.
Other Projected slabs
Slabs need to be projected on either side of
the walls. In Kitchen, the projection slabs are avoided if we go for a kitchen
cabinet below the slab level. Ti\his can be made in woodwork and flab marble or
cuddapah sheet can be placed on it to serve as a Kitchen slab. Ferrocement
panels can very well replace the whole wooden assembly in a very cheap manner. The externally projected sunshades
can be avoided with the help of sloping roof slab projection, which protects
the whole building. If it is necessary we can fix a funicular shell piece in
its place which acts as a lintel as well as a sunshade. Funicular shell is
major construction component in the Cost Effective Building and will be
explained in due course. This can also be used in Kitchen slabs, luggage stands
or in sunshades or in roof slabs.
ROOFING
In Kerala, the roofing of the houses were
thatched from very long back. The availability
Coconut leaves were abundant in Kerala. In
Tribal areas and other remote areas, long grass is used for thatch their
houses.
In some of the neighboring states, stone sheets of Cuddapah is used in paving
their roofs.
The life of the thatched roof is normally one
year and this has to be thatched annually. With the treatment of dipping the
thatch in a solution of copper sulphate and after drying applying one coat of
cashew oil, will extend the life up to 5 years. Except these type of
unstable roofing pattern, we can subdivide the other types of roof into
two.
1) Thatched roofing
2) Semi-permanent roofing
3) Permanent Roofing
1)
Thatched Roofinf
Thatching in Kerala is normally done with the
abundant leaves available in Kerala ie. Coconut tree leaf. Long Grasses, Bamboo
leaves & Palm leaves are also used for thatching the roof according to the
availability of the material in that
area. This type of Roofing has to be re-thatched every year. A special chemical
treatment of this tender roofing material will extend its life upto 5 years.
In Central Building Research
Institute (CBRI, Roorkee), one type of grass is used for roofing and they made
it as durable as a semi-permanent roofing. In this method over the wooden
supporting structure with 2’ x 2’ grid structure at the bottom and at the top
and grass layer is sand witched in between. Then the top surface is leveled
with mud. Then to protect the same from the rain, the top surface is plastered.
This extends the life of the roof upto 10 years and it is fire proof.
2)
Semi
– permanent roofing
This
type of roofs are not needed to be replaced annually or bi annually. The life
of semi-permanent buildings can be assessed upto 30 to 35 years. Semi permanent
roofs especially the Tile roofs will allow the heavenly cosmic rays to enter
your home. The permanent concrete roofs will never let these useful rays in.
The main types are..
a)
Tile
roofing with Mangalore Pattern tiles
b)
Asbestos
cement (AC) roofing
c)
Corrugated
Galvanized Iron (CGI)/ Aluminium sheet roofing
d)
Micro
concrete roofing (MCR) tiles
The above mentioned materials and its role in
roofing need not be explained (Item a-c). How ever all these semi permanent
roofs are not self supporting. They need a proper under support either with a
wooden structure of with steel pipes or angles. The item (d) is a new
innovation in the field of Cost Effective Construction method. The main
attractions of the MCR tiles are as follows.
a) The concrete mortar is used as a
raw material in the production of tiles instead of clay.
b) No heating required as a part of
production process as in the case of clay tiles, but curing in water for a week
is needed.
c) 200 tiles may be produced by a 3
nos workmen group among them one should be a skilled worker.
d) No sound will be heard during rain
falls.
e) You can make different couloured
tiled with the properly coloured cement mortar.
Permanent Roofing in CEC techniques
The
normal construction of the roof slab is done as a cast in situ concreting
process on a well prepared shuttering platform with steel reinforcement. In
residential buildings, the normal slab thickness is 10 cms or 4”. To reduce the
cost of roofing work, we have to
1) Reduce or eliminate the shuttering
2) Reduce the volume of concrete and
thus reduce the dead load
3) Reduce the quantity of steel used
Applying
one or more of the above conditions, some concreting methods have been
developed in the past. We can save the cost upto 30% in these methods of roof
concreting.
1) Filler slab
2) Funicular shell roofing
3) 3” thick concreting
4) Ferrocement slab roofing
5) Brick and concrete roofs in
pyramidal type roofing
1) Filler Slab
If strictly speaking, in Engineering
language, concrete in the tensile zone and steel in the compressive zone is
inert in normal conditions as far as the bending qualities of the Reinforced
Cement Concrete (RCC) is concerned.
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