Preliminaries
Preliminaries, usually shortened to prelims, are the project-wide costs of running a job that cannot be attached to any single item of work. Site setup, welfare, scaffolding, skips, plant hire, supervision and site insurance all sit here.
In practice for trades
Prelims are the costs that exist because the job exists, not because a particular task does. Nobody bills a customer for having a skip, but the skip still has to be paid for, and a price that only adds labour and materials has left it out.
The distinction that matters is against business overhead. Prelims belong to one job and end when it ends. Business overhead belongs to the company and carries on whether you are working or not. Your office rent is overhead. The welfare unit on a specific site is a prelim on that job.
Two things make prelims expensive. Most are time-related, so they scale with how long the job runs rather than how much work it contains. A two-week overrun costs another two weeks of scaffold, welfare and supervision, which is why delay claims turn on prelims more than labour.
The second is that on smaller domestic work they get skipped entirely. A sole trader rarely prices supervision, but the half day a week spent ordering and chasing is real, and unpriced it comes off the margin.
Worked example
A £48,000 extension runs for 10 weeks. Prelims: skip hire £900, scaffolding £2,400, welfare unit £1,100, site supervision at half a day a week (£1,400) and small plant £600. Total £6,400, or 13% of the job. Left out of the quote, that 13% comes off the profit.
Related terms
- Job costing: making sure prelims land against the job that caused them
- Charge-out rate: the rate supervision time is costed at
Work it out in FieldHive
Separate what belongs to the job from what belongs to the business with the Trade Business Overhead Calculator.
Trade Business Overhead Calculator→
