If you'll be doing the work yourself with the help of friends or family, make sure you have enough liability coverage to protect you if injuries occur. Contractors should have their own coverage, but ask to see a certificate of insurance showing proof of general liability, worker's compensation, and even auto insurance if commercial vehicles will be on your property.
Also, check your contract to find out who owns materials prior to installation. If materials will be stored on your property, you may need more personal property insurance. Verify that your contractor will protect your property while working, because your insurance may not fully cover damage from carelessness such as poorly covering an open roof.
If your project includes structural work or digging a basement, you may need a builder's risk policy, which covers damage from fire, wind, flood, collapse, and vandalism.