Lump sum or re-measurement: which contract suits your project in Oman?
The contract form decides who pays when the quantities change. Here is how the two common forms in Oman differ, in a table, and which one fits which kind of project.
The two forms compared
| Lump sum | Re-measurement | |
|---|---|---|
| Price | One fixed sum for the defined scope | Tendered rates × quantities actually built |
| Who carries quantity risk | Contractor | Owner |
| Design needed at tender | Complete, coordinated drawings | Enough to describe the work and estimate quantities |
| Bill of quantities | Firm bill or contractor's own; a schedule of rates for variations | Approximate bill; rates are the contract |
| Interim payments | Against an agreed activity schedule or measured progress | Against measured quantities each month |
| Variations | Valued at schedule rates or fair rates | Valued at bill rates; only scope changes are variations |
| Final account | Contract sum ± variations and claims | Full re-measurement ± variations and claims |
| Best for in Oman | Villas, apartment blocks, offices, fit-outs, hotels with fixed design | Roads, utilities, earthworks, plot infrastructure, refurbishment with unknowns |
| Main risk to owner | Paying a premium for risk transfer; variations if the design was incomplete | Final cost unknown until measured; needs a QS on site |
Choose lump sum when the design is finished
A lump sum only works when the contractor can price the whole job from the documents. If the drawings are incomplete, the contractor prices the uncertainty into the sum or leaves it out and claims it later as a variation. Either way the owner pays. For a building with complete architectural, structural and services drawings and a measured bill, a lump sum gives the cleanest price and the simplest administration.
Choose re-measurement when the ground decides
Earthworks, roads, utilities and anything below ground carry quantities nobody can fix from a drawing. A re-measurement contract accepts that and pays for what is built at competitive tendered rates, instead of paying a contractor to guess. It needs a quantity surveyor measuring as the work goes in and agreeing quantities monthly, so the final account is arithmetic rather than argument.
What both forms need
A clear specification, a proper tender with pre-qualified contractors, a payment regime with certification, a mechanism for valuing change and a record of instructions. In Oman, FIDIC forms are common on larger private work and the Oman Standard Documents on government work; both accommodate lump sum and re-measurement pricing. Whichever you choose, the price is only as good as the documents it was based on.
Common questions
- Is a lump sum contract really fixed?
- Only for the scope it was priced on. Changes to that scope are variations and are paid for. A complete design is what makes a lump sum hold.
- Can a project mix the two?
- Yes. A building is often lump sum with the earthworks and external works re-measured, each with its own section of the bill.
- Which is cheaper?
- Neither by definition. Lump sum prices include a premium for quantity risk; re-measurement prices can rise or fall with quantities. The cheaper option is the one that matches how certain the design is.
- Do I need a quantity surveyor on a lump sum job?
- Yes. Someone still has to check interim payments, value variations and agree the final account. The measurement burden is smaller, not absent.
How we help
Sources
- FIDIC — Conditions of Contract for Construction (Red Book)
- RICS — New Rules of Measurement (NRM 2, detailed measurement for building works)
- Projects, Tenders and Local Content Authority — Oman
This guide is general information based on the sources above and our experience in Oman. Rules and fees change; confirm the current position with the relevant authority before acting.
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