If damage is done to your possessions as a result of leakage, you should claim this damage to your contents insurance regardless whether the responsibility lies with third parties. This stems from a mutual agreement between insurance companies.
It is wiser to claim to the contents insurance, because it pays on the basis of replacement value opposed to liability insurance (e.g. from the landlord) that only pays market value.Important is the cause of the flooding. If you don’t know the cause, you’d better not try to guess it in order to prevent discussion on the policy conditions.
Your laminate flooring is damage due to leakage from the upstairs neighbours who mopped the floor with a bucket of water. This is not a chance event, after all, the neighbours could have not that the leakage would occur. Your insurance is likely to reject the claim, your damage should be recovered from the upstairs neighbours which is generally a difficult road.
You have damage to your home as a result of a leakage from a clogged drainage which is caused by for example a bird’s nest. You can claim damage to the contents on your contents insurance. Any damage to the building (paint, plaster) will be claimed by the landlord at his home insurance.
It’s important for both parties not to argue about the matter, before it’s clear what caused the damage. Parties should report the damage and file a claim with their own insurance company.