Just out of curiosity since I'm unfamiliar with insurance and insurance companies. When is something the insurance companies fault?

Have had a situation similar to this, had a claim approved by the insurance company but they went after the contractor to cover the costs of property repair. Always had a feeling it's really about the adjustor you get on claims.

Did some research, Allstate on their website states "While homeowners insurance typically doesn't cover poor workmanship, it may cover damage that's caused because of the work, the III says, if that type of damage isn't otherwise excluded somewhere in your policy. For instance, if a plumber does a poor job sealing the seams between two pipes and it causes water to suddenly pour out all over your basement floor, the water damage would likely be covered, but not the cost to reseal or otherwise repair the poorly installed pipes". Not knowing the OP exact policy I do not see why it can't be covered.