Insurance claims are denied for all types of reasons, from a peril not being covered or owner negligence. While in some cases the denial is justified, in others it's based on an error or misunderstanding of your policy. That's why it's important for you to address all denied claims in the appropriate manner, as explained by Money Crashers.
If you don't know your policy backward and forwards, now is a good time to become intimately acquainted. Understanding the details of your home insurance policy will allow you to catch any errors or mistakes that may have slipped by your adjuster. It will also allow you to understand policy limitations. For example, even if a peril is covered your policy may fall short of the compensation you're requesting. Also, revisit your claim and compare it to policy details. Make sure you have all the information you need before contacting your insurance company.
You also want to bring together some relevant evidence so you can properly appeal your claim. Make a list of what happened, when it happened, and what type of damage occurred. Back up your claim by taking pictures of the damage. You can also ask friends and neighbors who witnessed the incident to provide statements to the insurance company. It's also a good idea to establish your responsibility as a homeowner, which you can do by showing any safety features you've installed or presenting receipts for repair and maintenance bills.
Lastly, gather up all of the above evidence and file a formal appeal. Each insurance company has its own steps for appealing a denied claim, so be sure to follow these instructions. It's possible that your appeal will also be denied, in which case you should contact an attorney to help file suit. An experienced attorney will review your claim and your evidence to determine the best way to approach the problem.