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Estimating process

Preliminaries and site overheads.

Preliminaries cover the project-specific costs that cannot be allocated to individual work items. They include site supervision, welfare facilities, security, temporary services, and site accommodation.

Authored by Alexandr Vreme & Maksym Vasylkov
Published July 2026 — Next review July 2027

Who this guide is for

Estimators preparing tender submissions, project managers budgeting site set-up costs, and contractors who want to ensure preliminaries are fully covered.

Typical preliminaries items

• Site manager and supervisory staff (time-related)
• Site accommodation (offices, canteen, drying room, toilets)
• Temporary services (water, electricity, telecoms)
• Scaffolding, hoardings, and temporary works
• Security and fencing
• Welfare facilities and cleaning
• Traffic management and dust control
• Survey equipment and setting out
• Health and safety documentation and inductions
• Testing and commissioning
• Cleaning and waste management

Miniature example

A 12-week extension at £185,000 project value: site supervisor 12 weeks × £600/week = £7,200, welfare cabin hire £180/week × 12 = £2,160, scaffolding £3,500, temporary WC £450, security £600. Total preliminaries: £13,910 (approximately 7.5% of project value).

Common mistakes

• Applying a flat percentage without checking what the project actually requires
• Omitting preliminaries for smaller projects, assuming they are included in rates
• Not separating head office overheads from site-specific preliminaries