The purpose of preliminaries is to describe the works as a whole, and to specify general conditions and requirements for their execution, including such things as subcontracting, approvals, testing and completion.
NBS defines this in detail for all the commonly used forms of contract, listed in the Scope and Contents. NBS Preliminaries are not available as a separate product, but are included as part of NBS Building, NBS Engineering Services, NBS Landscape, and NBS Scheduler.
What are Preliminaries?
The specification of any project, whether shown on drawings or written, usually is said to consist of Preliminaries and Work Sections. Together they describe what is required to complete the Works in accordance with the Contract. If the Work Sections describe the nature of the work to be done, then what is contained in the Preliminaries?
The layout of NBS is based on the classification document Common Arrangement of Work Sections for Building Works (CAWS) published by the Construction Project Information Committee 
. This describes Preliminaries as:
Preliminary and general information and information relating to the Works as a whole; items for the Contractor’s general costs; provisional sums and other items for work by others or subject to later instruction.
The Code of Procedure which accompanies SMM7, the Standard Method of Measurement for building works, notes that the Preliminaries section contains those items that are not specific to work sections but have an identifiable cost which is useful to consider separately in tendering.
In short, Preliminaries relate to the cost-significant items required by the method and particular circumstances under which the work is to be carried out, and those costs concerned with the whole of the works rather than just Work Sections. These costs may either be ‘one-off’ fixed costs, such as the cost of bringing to site and erecting site accommodation (and subsequent removal) or time-related, such as the heating, lighting and maintenance cost for that accommodation.
The CAWS classification lists a series of headings for preliminaries, from A1- through to A5-. These cover general things such as information about the project, site, employer and consultants through to more detailed requirements on safety, security, method sequence and timing of the work, facilities and services and suchlike.
The A2- section includes clauses that are contract-specific and contain details of the actual form of contract and how it will be completed (although they do not contain the contract itself).
Sections A6- onwards relate to specific preliminaries for use in particular circumstances, such as demolition or site investigation/ survey contracts.
