What are preliminaries in construction?

Preliminaries, often shortened to prelims, are costs of organising and supporting construction work that are not conveniently priced as individual finished work items. Depending on the project and pricing document, they can include site management, welfare facilities, temporary supplies, site security and other shared arrangements. The preliminaries section can also describe the project requirements the contractor must price.

Ask what is included and how it has been calculated. Some costs arise once, such as establishing a site facility. Others depend on how long it is needed, such as continuing hire or site supervision. A breakdown can therefore contain fixed charges, time-related charges, or both. The RICS measurement rules provide that distinction; the actual pricing still depends on the project and the contractor's proposals.

There is no single percentage that establishes the right allowance for your job. Check the proposed duration, access, available services and who provides each shared item. If several trades are being appointed separately, identify what the household or main contractor must arrange between them.

For a fictional illustration, assume a welfare unit costs £200 per week to hire and is required for three additional weeks. The extra hire exposure is £200 × 3 = £600, before any separate transport, servicing or other stated charges. Those figures illustrate the calculation, not a market rate. Whether a contractor can recover an additional charge is a separate question under the agreement.

When comparing prices, keep each builder's original figure visible and record where an item is included, excluded or still unclear. Avoid adding an allowance again if it is already within another rate. Keep company overheads, profit and contingency identifiable so the same cost is not counted twice.

The self-build budgeting course explains how these costs fit into the wider project. If the prices are difficult to compare, Tender & Quote Review can turn the differences into a reasoned comparison and specific questions before you decide.