Specification can be defined as a written document, describing in detail the scope of work, materials to be used, and methods of installation, and quality of workmanship for an item of construction under contract, used along with working (contract) drawings in building construction.
When the architect has finalized the design of the proposed building to the satisfaction of the client, the next stage is to start construction. But before that, a complete set of working drawings and working details have to be prepared. While the working drawings will show what is to be constructed, the contractor will not understand how and in which manner the construction has to be done. For that purpose a complete set of detailed instructions has to be given to the contractor. These are called Specifications. While drawings tell us what is to be constructed, specifications tell us how it is to be constructed.
Specifications are a very important part of the construction document. Read with the working drawings and working details, it allows the Architect to pass on information to the Contractor about his exact intentions about the quality of work and the manner in which the sequence of construction is to take place. Contractors, while quoting for the job, will calculate the rates for different items of construction, based on the specifications for material quality and required workmanship etc. Even a small variation in the specifications will result in the change of the rate for an item of construction. Therefore it is very important to be exact in giving instructions in Specifications.
One can readily see that Specifications have a very important part to play in a Contract Document between the Owner and the contractor. In fact the contract is based on the drawings and Specifications prepared by the Architect. Well written Specifications can help avoid any legal disputes during and after construction.