Refusing Claim for no legitimate reason !!!!!!!

So we recently took home insurance with Discovery and already regretting it. Some tiles in our kitchen lifted up and the assessor said it was due to temperature fluctuations and so Discovery is refusing the claim. Why exactly ? It is a completely unforeseeable and unavoidable incident. It's like the wind blowing tree over onto your house. I am not happy about this and it needs to be looked at again. If Discovery continues to refuse to approve this claim I will cancel my insurance with Discovery. And move back to Momentum.