The basic function of a structure is to carry loads for which it is built and then to transfer them safely to the soil underneath. While performing this primary function it should cater for following aspects also.
2) Serviceability of structure.
3) Durability – time span for which it should serve satisfactorily.
4) Functional-to serve the purpose for which it is built.
5) Aesthetic-beautiful to look at-soothing effect.
7) Maintainability in service.
8) Adequate foundation.
9) Cost effective (economical)
Each of the above mentioned aspects has a bearing on the specification of a building to be constructed in one way or the other. Proposed building may be (i) Temporary (ii) Semi-permanent or (iii) Permanent, their specification also differ from each other in certain respects.
As soon as a building structure is conceived, specification of its construction comes into picture from that stage itself. First it comes in architect’s mind, next it is given a shape in the form of drawing in planning stage. Planning stage is a very important phase where an architect has to keep all the above nine aspects in his view and has to develop the plan of the proposed building to his maximum satisfaction. There may be number of constraints / obstructions / specific problems which may come in the way of execution of the work at site. All that need to be studied thoroughly at this stage itself and plans should be finalized accordingly. In the planning stage main function is to spell out clearly the layout of the proposed building (i) in space (ii) on ground and (iii) below ground. In addition to it, it covers specifications of work in a broad and general way. It doesn’t cover execution part of the work in detail.
Execution part of the work is covered in Detailed Specification of work which becomes Contractual Document and has legal binding in execution of the work to be strictly followed. Any violation of these Detailed Specifications of work not only affects the quality of work of the structure but some times leads to certain disputes. Disputes are referred to Arbitrators who consume considerable time to settle the issue. Hence framing of specification of a work is a very important activity and should be dealt with cautiously and efficiently. They should be framed in an unambiguous way and all activities to be performed under that item shall be spelt out explicitly. Any loophole left in the specification gives scope to the other party to take advantage.
AIMS OF SPECIFICATIONS
2) To work as a guide to the contractor as well as supervisory staff for quality execution work.
3) To protect interest of owner against low quality material, bad workmanship and enables him to reject it when needed.
4) To facilitate Contractor to procure quality material, adequate tools and appliances, machinery and plant for the work in time.
5) For proper estimation of work and provision of funds are needed for the work in time.
TYPES OF SPECIFICATIONS
1. General Specification : to give general and broad idea of the whole work with description of its items in brief – help in preparation of estimate and it also appears in notes in plans of the work.
2. Detailed Specification : becomes part of Contractual Document. It can further be sub-divided into three parts:
2) Technical specifications – gives in detail the technical aspect like quality of material, method of execution of work etc. of any special work contemplated and not covered in standard specifications. It also covers the machinery and equipment required for work and also specifications of proprietary commodities if needed for a work.
3. Standard Specification: Specifications of building work standardized by Central Public Works Department (C.P.W.D) or State P.W.D or other Government Department like Railways, Ministry of Transport, etc. They have their own Standard Specifications, which cover practically all normal items of work of a building construction.
Points to be kept in view for preparation of specifications:
1)Specifications should be properlyworded in an unambiguous way. Don’t use ‘if’ and ‘but’ to the extent possible. It should be concise and self explainatory.
2) Don’t miss any activity under any item of work. Such loophole shall be advantageous to other party.
3) Cover all items of works to be executed at site. Make non-scheduled items if they are not covered by scheduled items. For that purpose, detailed site inspection is a must beforehand. All obstruction at site – i) under ground (ii) on surface and (iii) overhead must be identified beforehand in order not to miss any item of work or activity associated with such obstructions.
4) There should not be any grammatical mistake in framing sentences. Punctuations should be correct. Same tense should be continued throughout. Avoid use of pronouns to the extent possible.
5) Specification should be framed in an unbiased way keeping principles of Law of Natural Justice in view and transparency in dealing. Interest of the owner and of the contractor should never be overlooked specially in items where risk is involved to carry out the work.
6) While framing specifications of certain items, the norms of Value Engineering and Value Analysis should be applied. They are good decision making tools when number of alternatives are available to do a job.
Specifications laid down either (i) in the form of plans or (ii) in the form of Detailed Specification for the quality of materials used, method of execution of work to be followed etc. are to be framed with great care. The reason being that they are connected with nine items mentioned above in one way or the other. Let us see how they are related to each other.
The building structure shall be strong enough to carry imposed loads. Therefore imposed loads need to be specified. Again strength of material which carries the load should be specified. How the work should be carried out should be brought out in specification in clear terms. You may give reference to I.S.Codes dealing in these aspects. The method of design of structural members should be spelt out clearly.
A building may be (i) Permanent (ii) Semi-permanent or (iii) Temporary. Specification should take care of this aspect. For semi-permanent and temporary structures some relaxation can be given in specifications.
Strength of a structure need to be ensured under various combinations of loads experienced by it. They are mainly Dead Load, Live Load, Wind Load and Earthquake force. Therefore each one should be specified and considered in the design. Earthquake zone and wind pressure zone numbers must be given in specification. Utilitywise buildings are graded. Hospital buildings are more important than residential buildings. Hence Important Factor for the building structure from its utility point of view needed to be considered in earthquake behaviour and needed to be specified clearly.
Normally complete floor is considered to be loaded with Live Load at a time in the analysis of a multi-storeyed building. But certain types of building under-go a peculiar loading pattern in case of Live Load application. Say for example a multi-floor, multi-bay R.C.C. framed school/college building – central bay having a class room and on either side of it are narrow verandah bays. In practice two typical loading pattern shall occur i.e. (1) When class is on, the central bay is loaded with Live Load and adjacent bays shall have no Live Load, (2) When class is over, the central bay gets unloaded and adjacent bays get loaded. The strength of the frame needs to be checked for these two critical loading patterns for its adequacy since in practice two pattern of loading are going to materialize. Prayer halls, assembly halls, cinema halls, having multi-storeyed multi-bay frames come under such category and need a careful check from strength point of view. If analysis of structure is done on computer software, these two patterns of loading must be fed as an input.
Normally in a R.C.C. framed multi-storeyed building architect adopts same cross-section of external column for its entire height from ground floor to top floor. This is needed to have same projection of column from wall face for the entire height of the building from elevation consideration. In R.C.C. column concrete takes compression and steel rods take tension. Therefore, it becomes essential to know the critical locations in the column run in the height where (i) concrete is subjected to maximum compression and (ii) where steel rod is subjected to maximum tension and they are within safe limits of permissible values of concrete strength in compression and of steel reinforcement in tension. In ground floor, column carries load from all floor hence this location is critical for maximum compression in concrete. Column in top most storey carries load from only terrace floor hence maximum stress in tensile steel is expected in column in top storey. As such reinforced concrete sections of column need to be invariably checked for two extreme conditions for its adequacy in strength. Usually in practice check at ground floor column is only made. STAAD-PRO 2003 version software takes care of this contingency of strength at all floor columns.
2. Serviceability of Structure:
Rigid and stiff structure is meant to carry load. Excessive sag, deflection, yield, elongation, twist, sway, and vibration make a structure unserviceable. Crack’s width in concrete in a reinforced section should not be excessive. liquid retaining surfaces of a structure should be crack-free o make it leak proof. I.S. codes specify their limitations from serviceability considerations and these specifications need to be followed strictly while planning a building structure.
3. Durability:
Durability defines life of a building structure. If the structure is permanent its serviceable life should not be less than 80 years. More and more strict specifications of quality of material and strict control over workmanship enhances the life span of a structure. Specifications for semi-permanent and temporary structure need not be so rigid as needed for permanent structure but they should cater for the need of semi-permanent and temporary structure. One should be more careful in framing specification when a temporary or semi-permanent structure has a possibility of converting it in a permanent structure in due course of time.
Besides input of quality of material and workmanship, environment has a significant adverse effect on durability of structure. Aggressive environment in industrial area injurious to the health of structure and responsible for rapid deterioration of structure need special care in framing its specification. Drying and wetting sequence of such structure leads to deterioration. Saline atmosphere in coastal areas has also detrimental effect on structures located near sea/ocean. Building structures in high mountainous altitudes, their situation in seismic belts need special care in specification. Buildings located in cyclonic or desert zone have their own peculiarities. Buildings in snow clad area needs special care in roof structure. Similarly intense density of rainfall need steeper slopes in roofing elements. Richer concrete mix, anti-corrosive treatment of reinforcing bar, extra protective cover to reinforcement rods, epoxy surface coating as a protective layer, special type of cements etc., become necessary specifications of the special type of works.
4. Functional requirement:
A school building cannot serve as a residential building. A residential building cannot serve as an industrial building. An industrial building cannot serve as a hostel building. Each building has its functional requirement. In a hospital building, ramp must be provided between two floors beside provision of a lift side by side. Operation room is a must in a hospital. Play ground is a must for school building. Therefore, such functional requirement becomes a specification for planning a layout of a building. It should be spelt out in explicit terms in the layout plans and Detailed Specifications. There are certain norms for each category of building and each has its own specifications high-lighting its requirement to make it functional in service satisfactorily. These specifications must be framed carefully in building bye-laws to cater for functional requirement. An architect has a very significant role in this field.
5. Aesthetic aspect:
Here the specifications are given by an architect in the form of a plan. Depressions, projections, curves, off-sets, proportioning of dimensions, arches, domes, cones, colour schemes are brought into picure by an architect while preparing plans to make a building beautiful. Aesthetic beauty adds to the value of a building also. Various colour schemes for a building can be developed now-a-days on a computer in a short time to select one.
6. Vaastu:
Vaastu teaches us how to align our dwellings to the tune of Nature’s Energies to derive maximum benefit out of them for our welfare and health. The specification of Vaastu tenets are adopted at stage of planning of layout of building similar to developing aesthetic aspect. There are certain Vaastu tenets for execution of building construction work also. These specifications should be followed in practice and Specified in Detailed Specifications in work.
Vaastu considers a building as a living organism – a Vaastu Purush. Vaastu shashtra is based on scientific doctrines. Institute of Vedic Vastu and Research Foundation (IVVRF), Indore (India) is an institution engaged in research work and training programmes on Vaastu discipline. Effect of Vaastu tenets can be studied with the help of scientific instruments available with namely Lecher Antenna, Electro stress meter, Dr.Gauss meter, Bio-feed-back energy tester, GDV Camera, TIF Detector, Radalert and Allergence air sampler etc.
7. Maintainability in service:
There are certain in-built items in Standard Specifications which are included in it as a protective measures for a building structure as a whole. These items infact serve as preventive measures to protect the structural components of a building structure against external ill effects and reduce maintenance activity of a building structure against external ill effects and reduce maintenance activity to a great extent in its service period. Leveling coarse below foundation base is provided to protect foundation from any ill effect from beneath. Plastering on wall is done to protect the brick masonry from external exposure to ill effects on both sides. Colour wash on plastering is done to protect plaster itself from exposure to environment. Flooring finish is provided to protect structural slab from any damage from outside and also protect it from its wear and tear. Weathering coat is given to terrace to protect roof from weathering effect and also serve as insulation for sun heat. Proper slope is given to roof surface to drain off rain water without any stagnation. Damp-proof course is provided to protect wall above plinth from dampness. Sunshades are provided to doors and windows to protect openings from rain and sun. Anti-termite treatment is given to protect building as a whole from ill effects of termite attack. Timber is protected by giving paint or polish finish. Reinforcement rods in R.C.C. work are provided with concrete cover to protect them from ingress of injurious elements from outside. Water proofing compounds are added in plastering mortars to protect external walls against seepage of water through them. Slabs are projected beyond external walls to protect them from rain water falling down from terrace. These items mentioned above appear in specifications and are directly connected with durability and maintainability of building structure as such.
Some of the items which are basically needed during maintenance stage are to be constructed and therefore must be specified e.g. manholes for drainage, ladder for access to over head water tank, railing for platform, compound wall with barbed wire fencing on top of it, adequate size of duct to facilitate any replacement or repair of down pipe or for painting or white washing etc. All such items which are needed for maintenance of the building at a later stage must be included in specifications for execution of work.
8. Adequate foundation:
Loads carried by building structure is to be transferred to soil underneath by foundation safety. Therefore specification of foundations is very important. It should take care of interaction of structure with soil. Soil may be rocky hard strata, it may be sandy or it may be clayey. Rocky strata doesn’t yield underload while sandy and clayey strata yield. Sandy strata bears load by frictional resistance between sand particle while clayey strata bears load by cohesion resistance between clay particle. Foundations differ from each other if they are to be laid over rocky strata, sandy strata or clayey strata mainly because of above mentioned behaviour of founding strata. Safe bearing capacity of soil is decided based on (i) pressure resistance considerations and (ii) settlement considerations. Sandy strata is controlled normally by pressure resistance consideration and clayey strata is controlled normally by settlement consideration.
Black cotton soil is problematic for founding a building structures. Minerals like montmorillanite and illite readily absorb moisture, swell and become slushy in rainy season. Whereas, in summer, they dry out, become hard and their surface gives rise to typical map pattern cracks, Such soils are known as expansive clay. Such soils are available in plenty in Indian sub-continent. Differential heavy pressure on structure of such Expansive clays result in distress in a structure.
Expansive clays have their active zone of 2 to 2.5m depth from ground surface. Below this depth is stable zone. Therefore in such soils foundation should be laid in stable zone. In framed constructions, a gap of 150mm depth must be left between soffit of plinth beam and ground surface. This makes provision of space for expansion of clay to avoid upward reaction of expansion on the structure proper. Specification of under-reamed pile foundation is useful for application in such situations. In such cases also a gap of 150mm is kept between ground level and grade beam for load bearing walls.
Shapes of footings have their own functional need. In clayey strata, square or circular shaped footing do carry more load in comparison to the capacity of strip footing of the same area. Again load carrying capacity of a footing on sandy strata increases with the increase in width of the footing. Load carrying capacity per metre width of square or strop footing. These aspects play an important role in decision making to specify type and shape of footing.
In an industrial area where waste discharge from a factory contaminates the ground water and proves to be injurious to the foundation, special care needs to be taken in framing specifications for foundations in such locations.
To do full justice to foundation of a structure, therefore, it is essential to have detailed soil exploration done at site of proposed building. Detailed Specification for soil exploration work need to be made. Type of laboratory and field tests to be conducted, number of bores to be taken, depth of bores and their location need be specified, soil exploration report must give its recommendations for type of foundation suitable for the location along with the depth of founding.
9. Cost effective (economical)
After taking care of all eight items mentioned above the last ninth item is that a building structure should be cost effective. This is of vital significance because it is closely connected with the purse of a client / owner. The structure should be cost-effective without compromising any of the other eight items connected with the structure.
Number of seminars, conferences, workshops and exhibitions had been organized. Indian Institute of Science, Bangalore have published ‘ALTERNATIVE BUILDING TECHNOLOGIES’ in November 2003. Number of alternatives have been suggested and economies have been worked out. They are more cost-effective when repetitive bulk work is involved like housing projects wherein saving in one is multiplied by number.
Buildings using cold formed steel sections are slowly gaining popularity in India. They are having number of plus points such as (i) Economical (ii) accelerated speed of construction (iii) Dry kit-of-parts (iv) Low weight (v) flexibility to make changes in internal planning in future (vi) No shrinkage or distortion (vii) Durability and longevity (viii) Ease of transportation, handling and erection (ix) provision of holes for service pipes and conduits (x) No form work. They can be used for multi-storeyed building-sheds-industrial structures, workshop structure, airoplane hangers, bus stands etc.
Adoption of a new technology in a routine way in mass is a slow process. Human tendency is to go in for a conventional way to be on safe side. Rigid and explicit worded specification of works involved in a new technology is a need to switch over to new technology with confidence. Green house, energy saving, rain water harvesting and pre engineered building technologies should also be covered in standard specifications.
Framing of specifications for a building construction work is a subject by itself which involves number of items as discussed above in brief. Thorough indepth knowledge of the construction practice, its magnitude, its constraints, available expertise to do the work and suitable technology for adoption need a judicious decision making mind above all. Any slip in this regard may cause many issues / disputes which shall adversely affect the work in many ways during the execution of work and / or even after completion of the work as well.
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