All policies are different, you should check your documents. A few common exclusions include:
Unforced entry – Leaving doors unlocked or someone accessing the property with keys leading to loss or damage.
Structural repairs – If you are having work such as extensions done on your property, you will need specialist Extension Insurance so your standard home insurance policy will not cover these damages.
Contractors – Normally contractors have their own insurance, so your policy will not cover their damages.