Construction Preliminaries (General Conditions) Calculator

Take it from the programme, not from the optimistic version in the tender letter. Every time-related item below runs for this whole span, including the weeks at the end when the value being certified has slowed to a trickle and the site staff are still there chasing snags. Under-stating the duration is the commonest way prelims come out short, because it discounts every line at once.

The site manager, the assistant, the engineer setting out, the storeman, the gateman. Anyone whose time is already inside a measured rate — the bricklayer, the electrician — is NOT counted here, or their cost lands in the estimate twice. Part-timers go in as a fraction: a visiting contracts manager one day a week is 0.2.

All-in means salary plus the employer's on-costs — national insurance or payroll tax, pension, holiday accrual, sick pay, training, and the vehicle and fuel if one comes with the job. That total is commonly 25 to 40% above the bare salary, and estimates that use the salary alone are short by exactly that margin on the biggest prelims item there is.

Welfare is not optional and is not negotiable down: the regulations set what has to be provided from day one, and an inspector who finds it missing can stop the job. Include the servicing — the toilets are emptied on a contract, and that contract runs weekly whether the job is busy or quiet.

Temporary power on a construction site is metered at commercial rates through a supply that also has a standing charge, and the lighting runs longest in the months when the daylight does not. Skips belong here rather than in the trades: waste arrives from every trade at once and no single rate carries it.

The hoist, the tower crane, the telehandler, the site-wide access. What makes this a prelim rather than a trade cost is that it is hired for the duration and charged whether or not it turned a wheel that week — the crane is on hire through the fortnight the steel was late. Plant hired in for one operation and sent back belongs in that operation's rate instead.

Everything paid once to turn a piece of ground into a site. Delivery and craning-in of the accommodation, the hoarding and gates, the temporary road or hardstanding, the incoming power and water connections, the site signage and first-aid provision. A delay does not repeat these, which is exactly why they are kept out of the weekly rate below.

Collection of the accommodation and plant, taking down the hoarding, disconnecting the temporary services, the final clean, and reinstating whatever the compound stood on. Routinely left out on the grounds that it is somebody else's problem by then, and it is not — it is in the contract and it lands in the last month, when there is no value left to certify against it.

Enter the sum including the preliminaries themselves, since that is what insurance and bonds are priced against and what the resulting percentage is normally quoted as. If you are building the number up from scratch and do not have it yet, an approximate figure is enough — it moves the value-related line and the percentage, and nothing else.

Contract works and public liability insurance are usually a fraction of a percent between them; a performance bond adds more, and a parent company guarantee instead of a bond adds nothing but is not always accepted. Collateral warranties and professional indemnity, where the contract asks for design, sit here too. These scale with the contract sum rather than with time, so a delay does not increase them — which is why they are held separate from the weekly rate.