Building insurance will cover kitchens and bathrooms if they are permanent fitted fixtures in the property. Again, cover will depend on how the damage was caused. If your kitchen or bathroom is ruined in a fire, flood, or storm, or subject to accidental damage or theft, then your insurance could pay out.
It is important to bear in mind that only integrated appliances will be considered by buildings insurance. If you are a landlord and provide appliances in your let, you might need to consider separate insurance if you want these covered too.