We take our estimates seriously. However, sometimes there are things we cannot foresee, no matter how thorough of an assessment and inspection we conduct. This is very rare but it does happen. For example, on one job the flue tiles needed to be broken out to accommodate the new lining system. In a properly constructed chimney, code requires a 1” airspace between the flue tiles and the surrounding masonry. The mason on this job felt it would be good to leave a larger void and fill it with loose sand. Thousands of pound of sand had to be controlled when we broke the tiles, adding unforeseeable cleanup time and trips to the dump. We have not seen this extreme bizarre variant before or since, but other creative masons have left us scratching our head in disbelief. Fortunately, these occurrences are infrequent. When they do happen, we do not try to make any $ on our labor or materials involved in addressing the problem–we simply charge you for the extra cost, at our cost. We feel that is a fair way of dealing with these problems. Generally, we know what the potential pitfalls are going to be (if any) and can communicate them ahead of time–and address what the increase in costs might be.