M&E Contractor Preliminaries Calculator 2025/26

Contractor preliminaries (or 'prelims') are the general costs of running the site that are not directly attributable to a specific measured work item. They include: site management staff, site huts and welfare facilities, small tools and plant, site fencing and hoarding, insurances, temporary services, health and safety measures, and project-specific requirements. Prelims are priced separately from measured work in a bill of quantities or schedule of rates. On M&E packages, prelims typically represent 8-15% of the package value.

Main contractor prelims cover the whole site and are typically 10-20% of the overall contract value. M&E sub-contractor prelims cover only the M&E team's site costs and are typically 8-15% of the M&E package. On a project procured under a main contract, the M&E contractor may benefit from main contractor site facilities (welfare, craneage) in which case M&E prelims will be lower. On design-and-build or specialist M&E contracts without a main contractor, M&E prelims will be higher as the M&E contractor must provide all site facilities.

Fixed preliminaries are one-off costs that don't change with project duration — mobilisation, demobilisation, initial site set-up, and specific method-related items. Time-related preliminaries vary with the project duration — site management salaries, welfare cabin hire, security, and similar running costs. When a project is extended, only time-related prelims change. Understanding the split is important for negotiating extensions of time claims and loss and expense — contractors are only entitled to time-related prelims for project overruns caused by employer-risk events.