Relationship Between working drawings and specification writing.
The primary role or function of working drawings is to convert design data into construction information and to clearly communicate that information to the building industry, code officials, product manufacturers, suppliers, and fabricators. If there is a conflict between the Drawings and Details on Drawings and the Specifications, then the Specifications will prevail. The higher “Order of Precedence of Documents” governs or prevails.
Working drawings and specifications are the primary working documents used by a contractor to bid and execute a project. Specifications are the written documents that go with the construction documents and describe the materials as well as the installation methods. They consist of precisely written documentation that describes a project to be constructed, supplementing drawings and forming part of the contract and describing qualities of materials, their methods of manufacture and installation into the project, workmanship, and mode of construction, in addition to providing other information not shown in the drawings including a description of the final result.
Many designers have considerable difficulty preparing a competent set of standard building specifications, partly because it demands a shift of gears by having to use a different medium to express design content—using written documents instead of drawing. It also propels the designer into the technical realm of materials that are not normally dealt with on a daily basis and which the designer may not be up to speed on.
Specifications should complement the drawings, not overlap or duplicate information in the drawings, and normally prescribe the quality standards of construction expected on the project. Specifications indicate the procedure by means of which it may be determined whether the requirements given are satisfied. Because specifications are an integral part of the contract documents, they are considered to be legal documents, and should therefore be comprehensive, accurate, and clear.
Specification writing has two principal objectives:
(1) defining the scope of work and
(2) acting as a set of instructions. Defining the scope of work is at the core of specification writing.
The required level of quality of the product and services must be clearly communicated to bidders and the party executing the contract and ensuring that the completed project conforms to this specified quality. Projects now generally incorporate the specifications within a project manual that is issued as part of the contract documents package along with the drawings, bidding requirements, and other contract conditions. The specification writer should ensure that the requirements are compatible with the methods that are to be employed and also that the methods selected in one specification are compatible with those selected in another.
A primary function of project specifications is to give detailed information regarding materials and methods of work for a particular construction project. They cover various components relating to the project, including general conditions, the scope of work, quality of materials, and standards of workmanship. The drawings, collectively with the project specifications, define the project in detail and clearly delineate exactly how it is to be constructed.
The project drawings and specifications are an integral part of the contract documents and are inseparable. The drawings reflect what the project specifications are unlikely to cover, and the project specifications indicate what the drawings are unlikely to portray. Specifications are also sometimes used to further clarify details that are not adequately covered by the drawings and notes on the drawings. Project specifications will always take precedence over the drawings, should the information on the drawings conflict with that in the project specifications.
Construction drawing is the general term used for drawings that form part of the production information that is incorporated into tender documentation and then the contract documents for the construction works. This means they have legal significance and form part of the agreement between the employer and the contractor.
The main purpose of construction drawings is to provide a graphic representation of what is to be built. Construction drawings should be concise and coordinated to avoid, wherever possible, ambiguity and confusion. Delays and misunderstandings can be minimized by properly coordinating the drawings. For more information, see Document control.
Specifications will detail the materials, standards, techniques, and so on required to carry out the works. Construction drawings provide a graphical representation, indicating the arrangement of components, detailing, dimensions, and so on. They may sometimes contain some of the information set out in specifications, but this should be avoided if possible, by referring to specifications rather than duplicating information. Where there is a crossover, care must be taken to ensure proper coordination so there is no confusion. If there is a disparity between the two, the specifications will tend to take precedence over the drawings.
A complete set of construction drawings tends to comprise floor plans, elevations, sections, and detail drawings, that together provide a complete representation of the building. On many projects, each major trade will have separate trade drawings, e.g. electrical, plumbing, and so on.
Construction drawings may be prepared by hand, but it is more common for them to be prepared using computer-aided design (CAD) (or computer-aided drafting) software.
More recently, the use of Building Information Modelling (software) has allowed the creation of a 1:1 virtual construction model (VCM), containing information allowing all objects in the model to be manufactured, installed, or constructed.
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