In all contracts, the stage is eventually reached at which both sides commit themselves to carrying out their agreed duties. In construction contracts – as in many others – this important point of commitment occurs when the signatures representing the two sides are placed on a document which, in legal language, is often referred to as an "instrument of agreement".
For the Sydney Harbour Bridge, this significant point was reached on 24th March 1924 when the representative of the contractor and of the Government of New South Wales each signed.
The actual document concerned is often surprisingly brief in relation to all the other material involved in the tender process. Sometimes it is only a single page, but it contains at least three important sections.
1. Project description
In order to reduce any later disputes as to what is or is not included in the contract, an accurate description of the work is required. A list of the titles of the main documents is included. There are four important items in this list.
- The conditions of Contract set out the rules under which the contract is to be carried out. These conditions include the procedure for settlement of disputes; the liability of the contractor for remedying defects; the procedure for subcontracting; commencement time, delays and completion and also such matters as safety and insurance.
Many larger authorities have a standard set of general conditions of contract but it is increasingly common for promoters/employers to assemble such conditions by word-processing from contract sections kept in memory. Standards Australia has a set of general conditions of contract: AS 4000, which refers to the promoter of the project as the "Principal".
- The drawings upon which the tender is based are clearly of crucial importance in defining the work required and so their exact, collective title is included in the list.
- The specifications for construction include the engineering requirements for the project in contrast to the general conditions which relate to procedures. The specifications include a great many numerical quantities such as the required strengths of concrete and steel.
- It is also customary for tenderers for major projects to include a "Schedule of Quantities and Prices" listing the costs of the many components that make up the tender submission. The value of such information can readily be seen when, as most frequently happens, additional work is needed somewhere or other on the job. This schedule title is therefore also included in the list. The Sydney Harbour Bridge schedule of quantities included twenty-eight items, adding up to 4,217,721 pounds, eleven shillings and ten pence. As might be expected, the largest single item was for the manufacture, supply, fabrication, delivery and erection of silicon steel at 1,749,215 pounds, ten shillings and sixpence. Another feature of public interest was the supply and laying of the granite for the pylons at 406,908 pounds, six shillings and eight pence.
Titles of other documents that would be listed would be those of the tender submitted and of the letter of acceptance of the tender. It will be noted that most of the documents referred to previously as the "tender documents" have become transformed into the "contract documents" and it is by this name that they will be referred to afterwards.
2. Statement by the contractor
The contractor undertakes to carry out the works as described and to put right any defects that are found, in return for the agreed sum of money.
3. Statement by the employer/principal/promoter
It is promised that the agreed sum of money be paid to the contractor on completion of the works and when any defects are put right.
It is at this point that the representatives of each party to the contract place their signatures on the document and the contract comes into operation. In a custom somewhat reminiscent of the Middle Ages, some companies have a company seal that can be affixed to documents in addition to a written signature.
The signatures that appear on the main contract for the Sydney Harbour Bridge were those of Lawrence Ennis for Dorman, Long and Company (as director responsible for the Sydney operations) and the Honourable Richard T. Ball, Minister for Public Works, New South Wales.