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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.

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