Planner answers

How do you calculate prolongation costs: Hudson, Emden or Eichleay?

Short answer: Site overheads are priced from records per day of delay. Head-office overheads are usually estimated with a formula: Hudson uses the tendered overhead percentage, Emden the contractor's actual overhead percentage from its accounts, and Eichleay allocates actual head-office costs by the share of the contractor's turnover.

  • Hudson: (overhead and profit % in the tender ÷ 100) × (contract sum ÷ contract period in weeks) × delay in weeks.
  • Emden: the same structure, but the percentage is the actual head-office overhead and profit from the contractor's audited accounts.
  • Eichleay: head-office overhead for the contract period × (contract billings ÷ total company billings), divided by the days of performance, times the days of delay.

Formulas are a fallback: tribunals prefer proven costs. Show that resources were held on the project and could not earn elsewhere. Chronaxis calculates all three side by side from the compensable days of the analysis.

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