What should preliminaries cover?

Site establishment, welfare, security, supervision, temporary works, plant that is not job specific, and the cost of complying with site rules.

How much contingency is sensible?

It depends on how well defined the scope is. Poorly specified refurbishment carries far more risk than new build to a fixed drawing set.

Does this handle retention?

No. Retention affects cash flow rather than cost, but check the contract terms before you commit.

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Construction Tender Calculator

A build up estimator for construction and contracting bids. Enter each cost element separately, add preliminaries, contingency and margin, and see the price to submit alongside the cost breakdown.

Materials

Labour

Plant hire

Subcontractors

Preliminaries

Contingency

Target margin

Total cost: £145,152
Bid price: £164,945
Margin value: £19,793

Preliminaries: £10,240. Contingency: £6,912.

Estimate only, not financial or regulatory advice. This is an estimate only, provided for general guidance. It is not tax, accounting, financial or legal advice. Check any figures with a qualified professional before relying on them.

How it works

Materials, labour, plant hire and subcontractor costs are entered as separate lines.
Preliminaries are added as a percentage to cover site set up, welfare, supervision and temporary works.
A contingency percentage covers the risk of variation and price movement.
Margin is applied on the full cost using the margin formula, not a markup.

Worked UK example

A refurbishment with 45,000 materials, 60,000 labour, 8,000 plant, 15,000 subcontractors, 8% preliminaries, 5% contingency and a 12% margin.

Base cost: 128,000.
Preliminaries at 8%: 10,240.
Contingency at 5%: 6,912 on the running total.
Total cost: 145,152, price at 12% margin: 164,945.

A submitted price of about 164,945, carrying 19,793 of margin before any variation.

Understanding your result

Preliminaries and contingency are the two lines small contractors most often leave out, and they are exactly what turns a profitable job into a break even one. If the buyer's budget will not carry them, the honest answer is usually to reduce scope rather than to strip the allowances.

Frequently asked questions

What should preliminaries cover?: Site establishment, welfare, security, supervision, temporary works, plant that is not job specific, and the cost of complying with site rules.
How much contingency is sensible?: It depends on how well defined the scope is. Poorly specified refurbishment carries far more risk than new build to a fixed drawing set.
Does this handle retention?: No. Retention affects cash flow rather than cost, but check the contract terms before you commit.

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