So this is a hypothetical question loosely based on genuine circumstances....
You buy a house, you take out buildings and contents on you new house.
A few years later you hire builders and they knock a supporting wall down(following correct procedures etc) creating a kitchen/diner
2 years later a significant water leak causes structural damage to one part of house and water damage to a number of rooms. This does not affect the kitchen/diner and it is in no way responsible.
Insurance claim starts, while reading up on what to do you discover that you should have spoke to insurance before starting any structural changes and your insurance is potentially voided.
Do you
A, say nothing pray the insurance doesn't find out.
B, confess to insurance company but risk losing payout which is expected to be 150k plus.