Several red flags here but my biggest question is, how does it cost 20k to replace all the joists and fix a slope problem but to replace one joist and no sloping problem it is 15k? Also, if they didn’t follow the contract and cut corners for cost saving reasons (using particle board) how can you be sure everything else was done correctly? They didn’t even pass those savings on to you so you know they’re saving every cent they can on their end.