In the event of a claim, the matter of the insured capital will be discussed. Is the building sufficiently insured? The capital sum to be insured will be sovereignly decided on by the co-owners. Fortunately, there are various tools for calculating the rebuild cost of the building (or complex of buildings). You can use a valuation grid provided by the insurer. Or you can arrange for a valuation report to be drawn up by an accredited external agency.
One simple solution is to take out first-risk cover (up to a certain amount). All damage up to this ceiling amount will be compensated in full without any discussion regarding the possibility of insufficient total insured capital.
Here is a fictitious numerical example in order to clarify this: you take out first-risk cover for the building of 1,000,000 euros. However, the total rebuild cost is 2,000,000 euros. In the event of severe fire damage, all damage will be compensated up to 1,000,000 euros but not one euro more. If you have no first-risk guarantee, then – in the case of damage amounting to 1,000,000 euros – you would receive just 500,000 euros in compensation on account of being underinsured by 50%.