The three mechanisms
They have neither the same cause nor the same treatment. Additional works differ from changes in quantities.
Additional works, covering works not provided for in the contract, covered in the article on additional works.
Price revision, adapting prices to movements in costs, covered in the article on price revision.
The final account of actual quantities, adjusting the amount to the works actually built, covered in the article on final account and actual quantities.
Confusing these three is common and leads to treating an increased quantity as additional work, which it is not.
| Mechanism | What it moves | Where it is provided |
|---|---|---|
| Additional works | The scope and the amount | Particular contractual clauses |
| Price revision | The amount, by formula | Particular contractual clauses |
| Final account | The amount, by actual quantities | Particular contractual clauses |
What the original package determines
Four elements decide what follows.
The form of contract, allocating quantity risk, covered in the article on measured and lump sum.
The quality of the description, determining what is included and what is not.
The existence of a revision clause, without which prices stay firm.
The unit prices bid, which will value any additional quantities.
The fourth point justifies looking at unit prices at analysis, and not only at the total.
The period to watch
Three moments when the amount starts to move. They concern variations, price revision and the final account.
Opening up existing fabric in refurbishment, revealing what surveys could not establish.
Changes requested by the client, the commonest cause of additional works.
Interfaces between packages, where a work was allocated to nobody, covered in the article on the tender documents.
The second case is the most legitimate and the worst documented: a change requested orally rarely reaches the final account in the terms in which it was understood.
What must have been provided for
Five points, all in the particular contractual clauses. They are checked before signature, not after.
The procedure for instructing additional works, written form and authorised signatory.
How such works are valued, by reference to the schedule prices or by another method.
The regime for price revision, existence, reference index and frequency.
The treatment of quantity variances, with any thresholds for renegotiation.
The arrangements for the final account and the period for challenge.
The absence of the first point causes most site disputes, since it lets each party maintain its own version of what was asked for.
The quantity surveyor's role after signing
Three tasks distinct from those of the upstream phase. They concern supervision, acceptance and the final account.
Verifying interim valuations and the final account, matching quantities invoiced against quantities built.
Classifying requests for additional works, separating what falls within the contract from what does not.
Documenting decisions, which become the material for interpreting the contract in any disagreement.
The articles in this branch
The article on additional works covers classification and price. The procedure is detailed there.
The article on price revision covers indexation. The formulas are explained there.
The article on final account and actual quantities covers the final adjustment. The mechanism is described there.
The article on developments to watch covers what is moving. The reforms are followed there.
This article sets out a method of professional orientation. It does not constitute legal advice.