This article in Insurance Journal notes a wide variation from state to state in how construction defects are analyzed:
On whether faulty workmanship is itself an occurrence, some states say yes, some states say no, some states are undecided, and some states say faulty workmanship is not an occurrence but the resulting damage is. “You also see differences in states in other issues as well."
It should be noted that there are Builder's Risk policies available that will cover contractors for construction defects. I have yet to come across a contractor that actually has such a policy, but that may be because those claims get resolved without the help of counsel.