$100K lesson - What contract language protects contractors when hidden conditions change the scope of a renovation job?

I have a clause for lack of a better term lol that states that ; “ This agreement and pricing herein are based solely on the visible conditions at the time of inspection.” Then I go into my actions if I find something that will change the work and pricing . There are a lot of ways to say it but it’s important that you say it and in a professional manner so you don’t come off like you are out to get them.