The following clause has been one of the first sections of my contract for any job we do for the past 10 years or so. Puting this into your contracts will totally protect you from situations just like this; 2. UNFORSEEN CIRCUMSTANCES/ UNDERGROUND OBSTACLES. Prices within this proposal are firm unless there are unforeseen circumstances that result in delays or obstacles. An example of such would be if contractor begins excavating digging or trenching and finds large boulders, large tree stumps, sewer drain, a piping situation that requires a plumber, etc. If such circumstances arise contractor will notify client immediately with an evaluation and proposed change in price or work. If the obstacle deems the job unable to be completed or if client decides the cost to proceed is too prohibitive the client is responsible for labor costs incurred until that point and for any materials used that cannot be returned Regardless, I'd find a way to compromise and leave him happy. We live in a day and age where just a few bad, unhapppy customers can really kill your reputation and cost you tons of jobs in the future. Everyone's using Angie's List, Google Local Reviews, BBB and tons of other places these days to sound off about their bad experiences. It used to be 10 years ago you could just kick a customer to the curb if they were wrong and you were right. Today, it doesn't matter if they were wrong. If you don't leave them at least somewhat happy they will sound off on places like Angie's List, leaving you with a bad reputation and pretty soon people are avoiding calling you just because a few bad reviews you got. I do anything and everything these days to make sure we leave our customers at least happy enough so that they don't go leave us bad reviews. And the goal is to leave them so happy that they go and leave a positive review, which is usually the case.