Three origins, three treatments
| Origin | Who bears it in principle |
|---|---|
| Discovery | the building's contingency, funded by the provision |
| Change of brief | the client, who chose |
| Error or omission | whoever produced the faulty document |
Those three origins produce the same visible effect, unforeseen work being carried out, but they share neither the same responsible party nor the same funding.
Identifying the origin before discussing price is therefore the first step, and the one most often skipped.
Discoveries fall under the dedicated clause, covered in the article on discovery clauses.
The process to write
Five steps, with one principle governing them all. Agreement precedes execution.
A written request, stating the object and its origin.
Pricing, within an agreed period.
The effect on the programme, stated explicitly, additional works almost always affecting the schedule.
Written acceptance before execution.
Traceability, each addendum numbered and linked to the original contract.
The governing principle: no execution without written acceptance. It is the only rule that protects both parties.
Applicable rates
A technical point that avoids most disagreements about amounts. The price of an addendum is fixed by a rule agreed in advance.
Three situations, to be provided for in the contract.
The item exists in the bill. The contract unit rate applies, making pricing incontestable. It is the strongest argument for a detailed bill, covered in the article on measurement in renovation.
The item is analogous to an existing one. The rate is set by comparison, by a method to be defined.
The item is entirely new. The rate is negotiated, and that is the least favourable situation for the client, who negotiates without alternatives.
A detailed bill therefore mechanically shrinks the zone of negotiation, which is its most concrete economic function.
The mechanisms of variations and interim valuations belong to the guide on measurement and specification. Their operation is set out there.
Why a verbal agreement does not suffice
Three practical reasons, independent of any question of good faith. They explain why writing protects both parties.
Content drifts. What was agreed orally diverges in good faith between the parties a few weeks later.
The origin is lost. A variation accepted verbally keeps no record of its origin, making it impossible to know who should fund it.
Proof is lacking. In a disagreement, whoever relies on a verbal agreement must establish it, which is rarely possible.
A written message confirming an agreement reached on site suffices, this being a question not of formalism but of record.
Budget drift by accumulation
A phenomenon specific to renovation, and rarely anticipated. Addenda accumulate through small successive decisions.
Each addendum looks reasonable in isolation. Modest amounts, accepted as the project proceeds, in a context where refusing seems petty.
Their cumulative effect often exceeds spectacular discoveries. The budget drifts by accumulation rather than by event.
The remedy is consolidated tracking, presented to the client at regular intervals, with the remaining contingency, connecting with the article on pricing with a contingency.
A client who sees the cumulative figure makes choices. A client who sees isolated amounts accepts.
What this means for a professional
Four rules.
Characterise the origin before pricing, discovery, change of brief or error.
Carry out no additional work without written acceptance, including under programme pressure.
State the effect on the programme systematically, not only on price.
Present a consolidated total at regular intervals, with the remaining contingency.
This article sets out drafting principles at the date of checking and serves professional orientation. It does not constitute legal advice and does not replace assessment of the individual case.