General
In these days of increasing cost of instruction of the dream of owning a
house particularly for low income and middle income family is becoming a
difficult reality. Hence it has become a necessity to adopt cost
effective, innovative and environmental friendly housing technology for the
construction of houses and buildings for enabling the common people to
construct houses at affordable cost. Building Centres (Nirmithi
Kendras) Established by the Govt. & HUDCO in all the districts are promoting
Low Cost Housing Technologies and are providing their Technical Advice and
Guidance services to the general public for enabling them to construct the
houses at an economical cost.
Low Cost Housing
Cost Effective Housing is a relative concept and has more to do with
budgeting and it seeks to reduce the cost construction through better
management, appropriate use of local materials, skills and technology but
without sacrificing the performance and life of the structure. It needs to
be emphasized that low cost housing does not mean houses constructed by
utilizing cheap building materials of substandard quality. A low cost house
is designed and constructed as any other house with regard to
foundation, structure, strength etc. the reduction in cost is achieved through
effective utilization of locally available building materials and
techniques that are durable, economical, accepted by users and not requiring
costly maintenance, Economy is also achieved by postponing finishing
and/implementing them in phases. Further, it aims at increasing the efficiency
of workers, minimizing wastage in design and space and applying good
management practices, so that shelter can be provided at prices which
people can afford.
Building Cost
The building construction cost can be divided into two parts namely:
Building material cost : 65 to 70 %
Labour cost : 65 to 70 %
The scope for effective means of reducing cost of construction lies with
minimizing the quantity of building materials which consumes less
energy. This is possible if one could follow a rational design procedure of
the efficient use of materials. Cost of reduction is achieved by selection
of more efficient material or by an improved design.
Avenues for reducing cost of construction - concept
The following are the avenues exist for reducing building construction
cost:
Reduce plinth area by using thinner wall concept.Ex.15 cms thick solid
concrete block wall.
Use locally available material in an innovative form like soil cement
blocks in place of burnt brick.
Use energy efficiency materials which consumes less energy like concrete
block in place of burnt brick.
Use environmentally friendly materials which are substitute for
conventional building components like use R.C.C. Door and window frames in
place of wooden frames.
Preplan every component of a house and rationalize the design procedure
for reducing the size of the component in the building.
By planning each and every component of a house the wastage of materials
due to demolition of the unplanned component of the house can be avoided.
Each component of the house shall be checked whether if it's necessary, if
it is not necessary, then that component should not be used.
Cost reduction is possible by eliminating redundant components. Ex: Avoid
plastering the walls, eliminating the use of plinth slabs in the
foundation.
Accept lower quality finishes like exposed brick work without plastering.
Reducing standards - providing jelly work in place of windows, no plinth
concrete
Cost reduction through adhoc methods
Foundation
Normally the foundation cost comes to about 10 to 15% of the total
building and usually foundation depth of 3 to 4 ft. is adopted for single
or double store building and usually foundation depth of 3 to 4 ft. is
adopted for single or double store building and also the concrete bed of
6"(15 Cms.) is used for the foundation which could be avoided.
It is recommended to adopt a foundation depth of 2 ft.(0.6m) for normal
soil like gravely soil, red soils etc., and use the uncoursed rubble
masonry with the bond stones and good packing. Similarly the foundation
width is rationalized to 2 ft.(0.6m).To avoid cracks formation in
foundation the masonry shall be thoroughly packed with cement mortar of
1:8 boulders and bond stones at regular intervals.
It is further suggested adopt arch foundation in ordinary soil for
effecting reduction in construction cost up to 40%.This kind of foundation
will help in bridging the loose pockets of soil which occurs along the
foundation.
In the case black cotton and other soft soils it is recommend to use under
ream pile foundation which saves about 20 to 25% in cost over the
conventional method of construction.
Plinth
It is suggested to adopt 1 ft. height above ground level for the plinth
and may be constructed with a cement mortar of 1:6. The plinth slab of 4
to 6" which is normally adopted can be avoided and in its place brick on
edge can be used for reducing the cost. By adopting this procedure the cost
of plinth foundation can be reduced by about 35 to 50%.It is necessary to
take precaution of providing impervious blanket like concrete slabs or
stone slabs all round the building for enabling to reduce erosion of soil
and thereby avoiding exposure of foundation surface and crack formation.
Walling
Wall thickness of 6 to 9" is recommended for adoption in the construction
of walls all-round the building and 41/2 " for inside walls. It is suggested
to use burnt bricks which are immersed in water for 24 hours and then
shall be used for the walls
Rat - trap bond wall
It is a cavity wall construction with added advantage of thermal comfort
and reduction in the quantity of bricks required for masonry work. By
adopting this method of bonding of brick masonry compared to traditional
English or Flemish bond masonry, it is possible to reduce in the material
cost of bricks by 25% and about 10to 15% in the masonry cost. By adopting
rat-trap bond method one can create aesthetically pleasing wall surface
and plastering can be avoided.
Concrete block walling
In view of high energy consumption by burnt brick it is suggested to use
concrete block (block hollow and solid) which consumes about only 1/3 of
the energy of the burnt bricks in its production. By using concrete block
masonry the wall thickness can be reduced from 20 cms to 15 Cms. Concrete
block masonry saves mortar consumption, speedy construction of wall
resulting in higher output of labour, plastering can be avoided thereby an
overall saving of 10 to 25% can be achieved.
Soil cement block technology
It is an alternative method of construction of walls using soil cement
blocks in place of burnt bricks masonry. It is an energy efficient method
of construction where soil mixed with 5% and above cement and pressed in
hand operated machine and cured well and then used in the masonry. This
masonry doesn't require plastering on both sides of the wall. The overall
economy that could be achieved with the soil cement technology is about 15
to 20% compared to conventional method of construction.
Doors and windows
It is suggested not to use wood for doors and windows and in its place
concrete or steel section frames shall be used for achieving saving in
cost up to 30 to 40%.Similiarly for shutters commercially available block
boards, fibre or wooden practical boards etc., shall be used for reducing
the cost by about 25%.By adopting brick jelly work and precast components
effective ventilation could be provided to the building and also the
construction cost could be saved up to 50% over the window components.
Lintals and Chajjas
The traditional R.C.C. lintels which are costly can be replaced by brick
arches for small spans and save construction cost up to 30 to 40% over the
traditional method of construction. By adopting arches of different shapes
a good architectural pleasing appearance can be given to the external wall
surfaces of the brick masonry.
Roofing
Normally 5"(12.5 cms) thick R.C.C. slabs is used for roofing of
residential buildings. By adopting rationally designed insitu construction
practices like filler slab and precast elements the construction cost of
roofing can be reduced by about 20 to 25%.
Filler slabs
are normal RCC slabs where bottom half (tension) concrete portions are
replaced by filler materials such as bricks, tiles, cellular concrete
blocks, etc., These filler materials are so placed as not to compromise
structural strength, result in replacing unwanted and nonfunctional
tension concrete, thus resulting in economy. These are safe, sound and provide
aesthetically pleasing pattern ceilings and also need no plaster.
Jack arch roof/floor
are easy to construct, save on cement and steel, are more appropriate in
hot climates. These can be constructed using compressed earth blocks also
as alternative to bricks for further economy.
Ferrocement channel/shell unit
provide an economic solution to RCC slab
by providing 30 to 40% cost
reduction on floor/roof unit over RCC slabs without compromising the
strength. These being precast, construction is speedy, economical due to
avoidance of shuttering and facilitate quality control.
Finishing Work
The cost of finishing items like sanitary,
electricity, painting etc.,
varies depending upon the type and quality of products used in the
building and its cost reduction is left to the individual choice and
liking.
Conclusion
The above list of suggestion for reducing construction cost is of general
nature and it varies depending upon the nature of the building to be
constructed, budget of the owner, geographical location where the house is to
be constructed, availability of the building material, good construction
management practices etc. However it is necessary that good planning and
design methods shall be adopted by utilizing the services of an
experienced engineer or an architect for supervising the work, thereby
achieving overall cost effectiveness to the extent of 25% in actual
practice.
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