Every answer and its explanation appears here once you have finished the path. Each one then links to the matching glossary entry, where the concept is set out in full with its worked example.
1. Three situations look alike on a site and do not call for the same thing. Which, and what does each require?
The site's normal progress, which is not disclosed; a change to the project, which calls for a variation; aggravation of the risk, which calls for a disclosure
The sorting is the heart of the module because it governs three different steps and getting the box wrong costs on both sides: disclosing what need not be disclosed clutters the relationship, failing to disclose what had to be opens a sanction. Normal progress is the widest and most reassuring box, and it is the default one. The answer bundling all three under a single disclosure removes exactly the distinction the module builds: a variation and a disclosure address neither the same people nor the same document.
Glossary entry · declaration-de-risque2. How does an aggravation of risk present itself in practice, and who decides it?
As a site choice, never as an insurance decision: it is decided in a works meeting, by someone for whom it is not the subject
That is what makes the duty so hard to discharge: the person creating the aggravation does not see themselves creating it, because they are solving a problem of schedule, access or supply. No channel spontaneously carries it to whoever would have to disclose, and it is the channel that must be built rather than the vigilance that must be requested. Waiting for a request from the insurer at renewal, as another answer suggests, puts the question twelve months too late and on the wrong side: the duty to disclose lies on the insured and runs during the works.
Glossary entry · declaration-de-risque3. An aggravation was not disclosed. What separates proportional reduction from avoidance, and on what is it judged?
Good faith: an omission in good faith leads to proportional reduction of the indemnity, bad faith to avoidance, and the line is judged on written traces, minutes and method statements
The gap between the two sanctions is the gap between a reduced indemnity and a policy that never existed, and it is decided on documents the site produces without thinking: minutes mentioning the difficulty and the solution adopted are the best evidence of good faith and the worst evidence of bad faith, depending on what was done next. That is why keeping minutes is an insurance subject and not only project management. The other answers name objective quantities, which makes them reassuring, when the line is one of appraisal.
Glossary entry · bonne-foi4. Proportional reduction applies. Where is it read in the policy?
Nowhere: neither exclusion, deductible nor cap, it is a silent retained loss, invisible at the three places people usually look
The three places people check their cover, exclusions, deductibles and caps, do not carry it, so a perfectly up-to-date cover summary can announce nothing of a retained loss reaching half the claim. That is what makes it formidable, more than its mechanism, which is simple. Confusing it with the underinsurance clause is the subtlest error and must be named: average sanctions an insufficient sum and cannot be argued, proportional reduction of indemnity sanctions an incomplete disclosure and is judged on good faith; two neighboring mechanisms, two different causes.
Glossary entry · tous-risques-chantier-car5. The same fact, disclosed before or disclosed after. What changes, and what does the clause decide on a multi-insured policy?
Only the date changes, and it turns a premium question into a sanction question; on a multi-insured policy, the clause decides who had to know and who had to say
A fact disclosed beforehand is rated, and it costs a few thousand euros; the same fact discovered afterward is sanctioned, and it costs a share of the indemnity. Nothing else has changed, neither the fact nor the risk, which makes the conclusion very easy to retain and very hard to enforce on a site. The second half matters just as much: on a policy written in the name of all, one insured's knowledge of a fact can bind the contract, and the clause says which one. The answer believing a variation can cure it confuses correcting the future with erasing the past.
Glossary entry · declaration-de-risque