A few points have been suggested based on experiences to reduce the construction cost of any structure in general and building in particular. A new word 'Costonomical' construction clubbing words cost and economical has been suggested. It is expected that engineers and architects will accept and appreciate this word giving a new definition to cost effective and economical construction.
IntroductionCostonomical construction means cost effective and economical construction of any civil engineering structure in general and building in particular following techniques which help in reducing the construction cost to an optimum value using locally available materials, improved and skilled labour and latest technology without sacrificing the strength, performance and life span of structure. The word costonomical has been developed by combination of cost effective and economical construction.
An efficient economy relies heavily on a high quality built environment, including affordable living and working spaces, network for transporting people and goods and reliable and constant distribution of energy, water and information. Due to larger amount of materials and energy associated with the construction, operation, maintenance and demolition of built environment severe environmental impacts may occur if these aspects are not properly taken into account.
Sustainability in construction through proper use of available resources and their consumption is very essential. Engineering design for sustainable construction by way of optimization and controlled consumption of natural resources, use of construction ingredients, recycled / manufactured aggregate etc. is also very essential. Methods and tools for sustainable construction practices covers technological development, advanced mix design, standard specifications, use of microscopy and microanalysis techniques, environment versus economic studies etc. These factors together also works in costonomical construction.
Stages of Costonomical ConstructionThere are two stages where economy can be achieved in construction. These are
- Pre-planning stage / Pre construction stage / Pre tendering stage and
- Post planning stage i.e. Execution stage which mainly consist of Management of execution of various items of construction. / Post Tendering Stage
All these stages can broadly be divided into following points to achieve economy in construction of any civil engineering structure
- Through Planning
- Proper Structural Designs
- Adopting proper specifications
- Making use of locally available materials
- Using pre cast / Pre fabricated elements in construction
- Reducing Overheads and managing work properly
- Using assumed industrial / agricultural waste materials like Fly ash and others
- Using latest construction techniques
- Energy /Light Resources
- Awareness and Training
(i) Through Planning:-This is a most important factor in achieving economic construction. Room size should be modular and as per requirement the furniture to be kept in that room. Many a time it has been found that a room size is un-necessarily a bit large serving no purpose. It happens because of not planning the room according to the furniture requirement. Many a people do not even know the sizes of furniture and simply decide room size randomly. Room size should be modular to avoid un necessary cutting of bricks. Only required number of doors and windows should be used as these are costlier than masonry walls. Further doors be located at about 100mm / 200mm away from corner of room as the space behind the door can be used to store brooms, sticks etc. Electrical open wiring system (conduit) be used then concealed as it is economical and easy to maintain. Room height should be only 2.8 to 3.0 m only. A room height beyond 3.0 m and up to3.5 m serves no purpose except increasing the cost. It does not increase thermal comfort considerably. From thermal comfort consideration, room height should be more then 3.6m to have comfort in an enclosure.
The plinth height should not be more then 45 cms. above finished road level. Similarly a foundation depth of 75 cms. is sufficient for low rise buildings. This will also depend on the soil condition the foundation needed to be laid over firm soil only. Taking dimensions more then these do not serve any purpose except increasing the cost. Built in cupboards are economical. It has been proved that load bearing structures are economical to framed structure by about 15 to 20% for low rise buildings. Further these structures also have been found to have equally better response to earthquake forces. Roof rain water harvesting is also one of the important factor and must be taken into consideration while planning any building. It raises water level considerably.
Group housing construction if adopted, it reduces overall cost of construction considerably. One planner, one designer, one contractor, one supplier all together makes a housing scheme economical by 15 to 20 %. It also reduces overheads considerably.
(ii) Structural Designs:-It has already been proved that our structures are generally over safe. The practice of rounding makes it further un necessary safe and costly as given below:
Designed quantity of reinforcement 4.02 cm2 ~ 4.1 cm2 (increase 2%)
Provide 10mm bars @ 12.7 cm C/C rounded to 12 cm C/C (increase 7-8 %)
At laying, one bar is always put extra for no reason again an increase of 7-8 %.
This way un necessarily quantity of steel is increased by 15 to 20 % extra increasing the cost of structure. Economizing on consumption of Re-bar, manufacturer of which substantially draws large quantum of natural resources, as also impacting the environment through pollution and heat loads during manufacturing.
Addition of extra cement in concrete is also a common practice observed. Over sized structural elements are constructed for no reason. Over reinforced sections must be avoided. These practices have to be curtailed to costonomise the cost of the construction. Structures should be designed as per IS codes. Arch foundation is not common in India, however if used may reduce construction cost by about 10 %. Under reamed pile foundation is very good in case of black cotton soils, however it is still not so common as it should have been. In case of load bearing structures for low rise buildings, instead of concrete plinth beam if brick on edge is laid in 1:4 cement sand mortar, a saving of about 5% can be achieved. It has become a common practice now a days to provide a PCC block in 1:4:8 cement concrete below actual footings. The reason is given that it is to have a level surface for actual footing. This block is put on a soil having a bearing capacity more than that of this PCC concrete used for block. It is actually a weak element is inserted in between foundation and sub soil. It is not clear what purpose this block is going to serve. It is an indirect increase of construction cost for no reason. This block is not required at all.
(iii) Adopting proper specifications:-This is also a common practice to change specification during execution work. These changes in private construction are very common and mostly changed on recommendations of mason or so called well wishers. These changes increase cost of constructions tremendously. If specifications have been decided as per funds available, why to change. And than owner says my funds have exhausted. It is a common say in public that if cost estimated is Rs.1.0 lack than actual cost is going to be more than Rs.1.5lack. Why? No one knows. And later on no funds remains with owner for white / colour wash. This item is then kept pending for want of funds for years together. It is therefore essential to stick to specifications decided. Change will increase the cost of construction tremendously.
Following changes are very common in construction:-
- Mosaic tiles are changed to stone flooring or ceramic/glazed tiles
- Flush door to paneled door
- Plinth height is raised (45 cms plinth height above finished road level is sufficient)
- Foundation depth is increased even for low rise buildings. (75cms Depth below ground level is good enough for low rise structures)
- Doors fittings are changed from steel to brass.
- Room height is increased from 2.8/3.0 to 3.0/3.2 meter.
- River sand to Narmada fine sand and so on.
(iv) Making use of locally available materials:-It has been observed at many places that people purchase fine sand from hundreds of kilometers at a very high cost mainly for plastering. Good plastering can be done using locally available sand getting it sieved through fine sieves. Moreover white wash or coloring is made on these plastered wall which hides the material used for plastering. But people do not bother for it and un necessarily invest a lot of money, making structure costly. At places where crushed stone dust is available which can be used as fine aggregate for concreting, people bring river sand at a very high cost making construction costlier. It has already been proved by many researchers that crushed stone sand can be used as fine aggregate and it does not affect the quality of work even than people are reluctant to use such materials. Even some engineers and architects do not recommend such materials. It is not desirable from them but of no use.
The reason may be a very wide gap between research and its implementation in actual use. This gap has to be reduced. Engineers and general public are required to make aware of recent developments and their benefits. There is need to have some correlation between field and research.
(v) Use of Pre cast/prefab constructions:-The best way to guarantee cost efficiency and quality at the same time is by use of high degree of industrialization in the whole construction process and construction industry. Use of pre cast / Prefabricate elements in construction is the first step of industrialization of construction industry which has already started. Pre cast / Pre fabricated elements are quite strong and durable. Use of these elements makes houses quite economical. These reduce construction cost tremendously. However its use is not very common even as on today. Use of these elements is limited to big cities only. Various pre cast elements are: Lintels, Wall Panels, Roof Panels, Pre Cast Beams, Concrete blocks, Ferro cement Jallies, Fly ash bricks, Ply wood / Glass Partition panels, Toilet blocks and so on. It is essential to develop awareness among people for their use.
(vi) Reducing Over heads and managing work:-The overall cost of over heads has been found of the order of 12 to 15%. This is a major figure. Reduction in it is very essential to costonomical construction. This is possible only by proper management of men, material, machineries and money. Making material and labour available as and when required can reduce construction cost to a considerable extent. Group housing schemes can reduce overheads considerably by employing one watchman, one guard, one tap connection, one supplier of materials etc. Time cost factor studies show that considerable overheads can be reduced by reducing total duration of project however even owner does not take care to complete the work earliest possible to reduce these overheads.
Management of all activities effectively and efficiently is very essential for timely completion of project. It reduces over heads. Making men, materials and machineries available timely completes the project early making it economical. BoT system has increased its importance manifold. Contractors have realized its importance however its importance to common people is not yet known. An owner who is constructing his own house never bothers if house completion gets delayed. He blames for others for not supplying material in time or for not coming labour in time and so on. However he never thinks that what measures he himself has taken, what precautions he has taken for early completion of work. Proper management is therefore very essential for costonomical construction.
(vii) Use of waste materials:-There are good amount of assumed industrial waste and agricultural waste materials available. If these materials are transformed in good usable products, not only cost of construction can be reduced, rather a control on environmental pollution can be achieved. The quantities of some of the waste materials produced are given in Table 1. This table also shows the likely use of these waste materials. Some of these materials have been transformed in usable products; however there is still sufficient scope for their use. Effective management of waste and exploring alternative resources, covering waste minimization, recycling for reuse and opportunities thereof etc. are very essential.
|Table 1: Useful Waste Materials|
|S.N.||Assumed Waste Material||Quantity Produced Millions Tons per Year||By Product of / Others||Likely Use|
|1||Fly Ash*||200||Thermal Power Stations||Bricks, Concrete|
|2||Agro Waste||150||Agriculture||Particle Boards|
|3||Industrial Waste||125||Industries||From various Industries|
|4||Domestic & Municipal Waste||300||Household||Can be recycled|
|5||Phospho Gypsum||05||Phosphoric Plant||Gypsum Board|
|6||Ground Nut Waste||02||Oil Refineries||Boards|
|8||Coconut Waste||02||Coconut||Coir Acoustic Board|
|9||Red Mud||04||Aluminum plants|
|* It is mandatory to use fly ash for construction if available with in a distance of 50 to 100 Km from thermal Power Station.|
Other waste materials those can be transformed in good usable materials are: Bamboos, Paper Waste, Lime Sludge, Molten Slag, Cotton Stalks, Straw, Sisal Fiber, Saw Mill Waste, Jute Stalk, Lathe Waste, Marble Scum, dismantled construction Waste, Stone Dust, Nylon Fibers, Foam Waste, Nylon, Banana Leaves etc.
(viii) Using Latest Construction Techniques:-Latest construction techniques like Rat trap bond, Concrete hollow or solid blocks, Fly ash bricks, Brick noggin, Brick Shell, Pre cast elements, Ferro cement construction etc should be adopted. These materials do not only make structure economical, but make structures eco-friendly. Various Boards like E-Board i.e. Mineral bonded particle Boards, Cement Bonded Particle Boards, glass fiber bonded boards, etc are available in market. These boards can be used for partition walls which reduce cost of construction tremendously. Use of Powder Coated Aluminum windows reduces window cost by about 10 percent. Every one knows importance of use of solar heaters, but how many people use it. People are not aware of this technology or reluctant to use it.
(ix) Energy/Light Resources:-Rapid industrialization and population growth since World War II have resulted in the consumption of enormous amount of the earths resources and energy, causing unprecedented environmental changes on a global scale. Fortunately, mankind has recognized the nature of the problem and developed the concept of 'Sustainable development.'
As such use of natural resources of energy like Sun, Wind and Rain are very essential elements assisting for costonomical construction and must be taken into consideration. Use of thick curtains to windows reduces solar radiation in an enclosure making thermal comfort condition in side desirable. It indirectly reduces power consumption in case of air conditioned building considerably. Simply tightening the opening reduces electric consumption by about 10%. Photo chromic glasses though have high initial cost but are found economical in long run if used for windows. Dusting of lamps at a regular interval of time can save energy to some extent. If freeze is put at a temperature of 37 to 40 degree F considerable energy can be saved. Use of CFL lights or LED illumination system with 5 star rating also saves energy to a very great extent and however has become common. There are various ways those can be used to reduce energy consumption or to have thermal comfort in an enclosure. Energy efficient glasses if used to windows, they transmit only 70% heat and saves cost of air conditioning by 30%. Solar glazing blocks for masonry works as radiation barrier and transmit less heat into an enclosure. Rain water harvesting helps in raising water level which is in scare. A duct open to sky if could be provided in a house, tremendous energy can be saved creating thermal comfort conditions in an enclosure. This has been tried and found very effective in summer. A temperature gradient of 5 to 6 degrees centigrade is easily achievable.
(x) Awareness and Training:-It is one very important factor needs attention. Extensive awareness campaign and demonstration among general public and Engineers and Architects are essential. It is to make them familiar with these latest techniques. Skill up gradation programmed training to masons and labour is an essential requirement as these are the persons who have to apply these techniques in construction. Many good and eco friendly materials have been developed but they are not much in use. Users have to be made aware of these materials. They have to be convinced that these materials are not of cheap quality. They are equally durable and economical. Unless users are convinced, they will not use it. It is the responsibility of Engineers and Architects. They have to recommend these materials and techniques in construction. Engineers and Architects therefore are required to be made familiar with these materials which are eco friendly, economical, durable and equally strong and latest construction techniques.
As such if these above points discussed are taken into consideration during planning and execution, a considerable economy in construction can be achieved. More over these points will make environment clean which is an essential need of today's and tomorrows generations to come.
|Figure 1: Plan of a Costonomical House|
|Figure 2: Details of Pre cast Pre stressed Column and Beams|
Case StudyA small house is shown in Figure 1. Figure 2 and Figure 3 show details of Pre cast Pre stressed columns and beams and their arrangements. The specifications used are given below and its estimated cost is shown in Figure 1. This house has been designed as Eco friendly house using latest construction materials and technology. It costs only Rs.2916 per square meter. The specifications are
- Foundation- Pre cast column embedded in M20 Concrete block of 90cm*90cm 300mm thickness 75cms below G.L. Standardized soil is filled above concrete block up to ground level as shown in figure.
- Masonry- Cement bonded particle boards 12mm thick as partition walls. Needs no plastering.
- Openings- Powder coated steel doors and windows for all openings.
- Flooring- M20 grade cement concrete flooring with Chicken woven wire Mesh.
- Roofing- Cement bonded particle boards resting on Pre cast Pre stressed 100mm thick beams, over which thin goge wire woven mesh is laid in 20mm thick 1:4 cement sand mortar.
|Figure 3: Details of Column and Foundation, Beams and other details|