Structural damage insurance is compulsory when you have a property built or renovated by professionals. It allows you, if you notice a construction defect or poor workmanship up to 10 years after delivery of the site, to be compensated by the Structural Damage insurer for the amount of the necessary work.
The latter will then turn against the project manager / company responsible for the property disorder in order to be itself reimbursed under the mandatory ten-year guarantee (or ten-year civil liability).
DO insurance must therefore in principle be "backed" by the ten-year guarantee of the project manager.
Without a professional contractor, there is no ten-year Civil Liability, and therefore the Structural Damage insurer has "no one" against whom to act next to recover the funds it has advanced to the insured.
In the absence of a prime contractor, it will be much more complicated to subscribe to a structural damage insurance contract.