We just went through arbitration with them over pier failure which had eventually caused in excess of $80K damage to out home by the time they had 4 of their so-called warranty callbacks. The original damage repair was quited at around $7K to fix. They'd rather spend more money on a lawyer than spend less to repair the damage they orginally caused. Our personal costs for arbitration and reports was in excess of $8K. We were just fortuniate enough to have the money to fight them which many don't. That did not even include attorney fees. That "certified engineer report" comes from Texas certified by an engineer who never sees the work that has been done. Before you do anything, spend 2 to 3 hundred $'s for a local engineer's report. And if you do need foundation work get ay least three estimates. This was our personal experience with onshan while other's may have different results,