Specification And Estimation (unit 1).pptx

Unit 1 Specification

Unit - I • Necessity of specification, importance of specification. • How to write specification. • Types of Specification. • Principles of Specification writing. • Important aspects of the deign of specification. • Sources of information. • Classification of Specification.

Specification Specification deals with the methods of execution,

qualities of materials, nature of labour to be employed, proportion in which materials are to be mixed, measurements of work done etc.,

The information regarding the quality of materials and workmanship is conveyed in a separate contract document which is known as the specifications for the work.

Specification. . . ? • A specification is a specific description of a particular subject. • An engineering specification contains detailed description of all workmanship and materials which are required to complete an engineering project in accordance with it’s drawings and details. • The technical drawings of a structure will show the proportions and relative positions of the various components of the structure. • The data regarding the drawings, quality of materials and workmanship is conveyed in a separate contract document which is known as the “specifications” for the work. • Thus the drawings with the engineering specifications will completely define the structure.

Necessity of specification 1.

The cost of the unit quantity of work is governed by it’s specification.

2.

Specifications of a work are required to describe the quality and quantity of different materials required for a construction work and is one of the essential contract documents. Thus a contractor can make a programme to procure the materials required for a project and the owner can check the quality of materials conforming to the specifications.

3.

This also specifies the workmanship and the method of doing work. Thus, specification of a work serves as a guide to the supervising staff of the contractor as well as to the owner to execute the work to their satisfaction

4.

A work is carried out according to it’s specification and the contractor is paid for the same .Any change in specification tends to change the tendered rate.

5.

As the rate of work is based on specification, a contractor can calculate the rates of various items of works in a tender with his procurement rates of materials and labour.

6.

Specification is necessary to specify the equipments ,tools and plants to be engaged for a work and thus enables to procure them beforehand.

Importance of specification. • The drawings and specifications form two important contract documents. • The information (such as dimensions, types of construction, etc.) which can be easily expressed graphically are put up on the drawings. • On the other hand, The instructions which can be easily expressed well in words are written in the specifications. • But generally, the provisions in specifications are given more legal strength and most of the contracts state that in case of discrepancy between the

drawings and specifications, the provisions of the specifications shall govern. • Thus, the specifications play an important part in construction work and

heavy responsibility is attached to the specification writer for his job.

Types of Specification General Specifications / Brief Specifications In general specifications, nature and class of works and names of materials that should be used are described. Only a brief description of each and every item is given. It is useful for estimating Detailed Specifications:

the

project.

The

general

specifications do not form a part of contract

document. The detailed specifications form a part of a contract document. They specify the qualities, quantities and proportions of materials and the method of preparation and execution for a particular item of works in a project. The detailed specifications of the different items of the work are prepared separately and they describe what the work

should be and how they shall be executed. While writing the detailed specifications, the same order sequence as the work is to be carried out is to be maintained.

Principles of Specification Writing • The specification of the work are written by the engineer before it is known who the contractor will be.

• It should be noted that the technical knowledge of the engineer is of little value as far as writing of the specifications is concerned unless he can make his ideas clearly understood by the other contractors, workmen, supervisors, etc., many of whom may have little or no technical training.

Principles of Specification Writing Contd… 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Subject matter Grammar Abbreviations Development of style Selection of words Accuracy Conflicting requirements Practical limits and commercial sizes Clearness Fairness

Principles of Specification Writing… Contd Subject matter: The subject matter of the specifications should relate to the information required after the contract is given to a particular contractor. The requirements which are to be enforced should only be included in the specifications. The use of cross references should be reduced to a minimum. Grammar: All sentences of the specifications should comply with the rules of grammar. The style and tense should remain the same throughout. The hyphens, commas and semi-colons should be used as and when required and the sentence should be framed in such a way that the addition, omission or misplacement of a comma does not alter the sense. As far as possible the pronouns, especially relative pronouns, should not be used. It is advisable to repeat a noun. Abbreviations: Only those abbreviations which are well-known in the building industry should be used without giving definitions. The use of abbreviations facilitates easy understanding and reduces the typing work without sacrificing clarity.

Principles of Specification Writing… Contd Development of style: It must be remembered that the main aim of specification writing is to present a clear picture of facts and no attempt should be made to make an elegant and impressive style. The specifications writer should develop his own style of arranging his ideas with clarity and brevity. There is plenty of scope for improvement even when the specification is being copied from a printed specification of some manufacturer. Selection of words: While writing specifications, only suitable words with desired meaning should be used. The unfamiliar words or words having more than one meaning should never be used in the specification. Also the use of unusual technical and trade expressions and semi-legal words should not be used.

Accuracy : The information given in the specification should be complete and correct, otherwise the contractor may claim for any extra cost due to damage occurred to him by the misleading information supplied by the owner. Also, care should be taken to see that information is not repeated in the specifications.

Principles of Specification Writing… Contd Conflicting requirements: The clauses of the specifications should be framed in such a way that no conflicts of any type result. For instance, while writing the specification for driving piles, both the requirements, namely, penetration of the pile and its bearing capacity, should not be mentioned. In some cases, the piles may have reached the required penetration. But the specified baring power may not have been developed. In other cases, the reverse may happen. Practical limits and commercial sizes: The specification should be frame while keeping in view the practical limitations of materials and workmanship and they should not specify practical impossibilities. Also the specification should specify use of commercial sizes and patterns of the materials. It becomes expensive to manufacture special size and it also takes more time to prepare such sizes. For instance, the steel sections and steel bars are readily available in certain sizes only. If other size is specified, a special order is to be given, which requires more time and special rate for its delivery.

Principles of Specification Writing… Contd Clearness: The specification should be clear as far as possible and it should be observed that their meaning is not left by the engineer. In fact, both the particles owner and contractor- should follow the same sense. Also the specification should state what the contractor should or should not do. Fairness: The specification should be fair and they should not be framed in such a way so as to throw all the risks on the shoulders of the contractor. Also, all likely hazards, difficulties, etc. should be specified in the specification so as to give a clear picture of the work to the contractor will assume all such risk and will put a higher price in his tender to accommodate all such risks, in case they come up.

IMPORTANT ASPECTS OF THE DESIGN OF A SPECIFICATION •

Changes: The designer of a specification should be given an opportunity to observe the field application of his specification. Such a procedure will help in increasing the knowledge of the designer and he may utilize this knowledge, if found necessary, to change, to expand, to improve, to modify or to strengthen his specification for future works.

•

Clearness : The design of a specification should be such that it brings the limit of misunderstandings and misinterpretations to a minimum. Such a design will naturally minimize the chances of disputes.

•

Co- operation: The specifications should be designed to provide a motive of co-operation between the engineer and the contractor. The engineer, with the help of a well-designed specification, can assist, encourage and guide the contractor, with the help of a well-designed specification, can combine labour and materials to the best advantage of getting the desired end product. Thus, a well-designed specifications would prove useful to both – the owner and the contractor.

•

Cost : The initial cost of a well- designed specifications may prove to be more but it forms a small fraction of the cost incurred in extra claims, delays, disputes and bad workmanship due to poorly designed specifications.

IMPORTANT ASPECTS OF THE DESIGN OF A SPECIFICATION Contd… •

Flexibility : The specifications should not be rigid. But they should be dynamic in nature and should be adaptable to new inventions, to new ideas and to new methods of construction.

•

Product control: A well – designed specifications aims at product control by the

available equipment of the contractor. The automation can also be adopted with advantage to achieve product control. The advantages of product control are-fewer samples for testing, reduced costs, early completion and uniform work. •

Designer : The specifications should be designed by competent persons, possessing

wide experience and high ability. This is a very important factor influencing the achievement of a goal of specification. If the work of writing the specification is entrusted to a professional man, it simply results into the copying of paragraphs from the existing specifications.

SOURCES OF INFORMATION Following are the main sources of information from which the information regarding the specifications of civil engineering work can be gathered or obtained: 1. 2. 3. 4. 5. 6.

Contract drawings Previous specifications Requirements of owner Site Investigations Standard specifications Trade catalogues

SOURCES OF INFORMATION Contd… • Contract drawings: The draft drawings prepared in the initial stage of the project contain useful details which are of considerable assistance to the writer of the specifications. • Previous specifications: In majority of cases, the specifications of the executed jobs or jobs under execution can be used as basis for the preparation of new specification of similar job. This procedure expedites the work. However, care should be taken • Requirements of owner : If the owner desires to incorporate certain requirement in connection with the job, the same should be suitably included in the specification of the work.

SOURCES OF INFORMATION Contd… Site Investigations: It is desirable that the specifications include the fullest information for the existing site conditions such as extent of site clearance work, soil conditions, etc. The contractor is thus kept away from making unnecessary allowance for certain factors. Standard specifications: The reference can be made to the relevant standard specifications and thus, it permits a considerable reduction in the length of specification clauses. It also helps the contractor in easy understanding of the specification requirements. Trade catalogues: For specifications of the proprietary commodities the reference can be made to the catalogues supplied by the manufacturer of that item. However, if an article is produced to a number of different patterns it is necessary to quote the correct catalogue reference.

Classification of Specification Depending upon the method to be used in describing a material or method of installation, the specifications can be classified into the following three categories:

1. Open specifications 2. Restricted specifications 3. Closed specifications

Classification of Specification … Contd Open specifications : An open specifications gives the physical and chemical properties of the material, the tests it must comply with or the results expected and such other information. But it never gives a specific item of equipment or a trade name or a proprietary commodity. The open specifications are generally used for public works and a true open specification is one which of lays down minimum standards and which can be easily fulfilled by several manufactures within permissible limits. Following are the advantages of the open specifications: • Basic materials: They are suitable for basic materials such as cement, steel, sand, etc. because the standards of such materials can easily be laid down without regard to the manufactures. • True competition: They provide an atmosphere of a true competitive of a true competitive market in which the new products have equal chance to compete with the old and well advertised products. It may also result into a lower cost the owner.

Classification of Specification … Contd Following are the disadvantages of the open specifications:

1. Checking and testing : The checking and testing for each material or product mentioned in these specifications may prove to be time-consuming. 2. Control over the quality : It is feared that if they are not properly drafted, it may result into losing a firm control over the quality of the products. 3. Effect on design: If a particular product or material fulfills the permissible variances with respect to size, weight, etc. mentioned in these specifications and if the contractor insists to use such product or material , the architect in some cases have to change or alter the design of the project to accommodate such product or material. 4. Time –Consuming: These specifications are by nature lengthy and hence, the architect or specification writer has to spend his valuable time in framing them.

Classification of Specification … Contd RESTRICTED SPECIFICATIONS: The material is described by the choice of the contractor is limited to two or more manufactures or distributors. Disadvantages of a Restricted Specification: • Problems of design: The possible use of various product mentioned in the approved list should be carefully considered. In fact, only such products should be included in the approved list which will not disturb the space requirements, connections, equipment for installation, details and other factors of the project. • Quality product: It should be seen that the products mentioned in the approved list are more or less in reality equal in quality and price. If the price of even one of the product mentioned in the approved list is substantially lower than those of others, it will eliminate the competition and the purpose of restricted specifications will not be served.

Classification of Specification … Contd Closed specification : In case of a closed specification, the material or product is designated by a trade name mentioning catalogue number, manufacturer and sometimes a particular distributor from whom the product is to be purchased. It is sometimes argued that the closed specifications result in avoiding the competition

and in increasing the cost of the project. This argument has no force in the sense that the material or product which is included in closed specifications has stood the test of time and has proved its adaptability in respect of quality and price both. The architect is the agent of owner and hence, he will select only those materials or product to be included in the closed specifications which will be helpful in turning out a satisfactory completed project.

Classification of Specification … Contd Following are the advantages of the closed specifications: • Completion of drawings: the architect can complete the drawings of the project before the tenders for the work are invited, when these specifications are adopted. As the complete details are known, the designer can accurately decide the details such as room dimensions, foundations, fastenings, fittings, etc. • Choice of owner: The owner has a choice of the material he prefers and he can thus enjoy the special features of a particular product.