Asking for a detailed bill during Rehab

[Kyle McVay]

I would like to ask my contractor to provide a detailed bill prior to releasing any additional funds. 

We have had a couple of minor misunderstandings despite the quote being in writing. For instance, we informed him we'd do ALL the demo. We have 4 kids 13+ who are still at home. The college student came just to help knock down walls. Anyhow, we didn't finish the bathroom demo on the tub/shower the first weekend. However, he was scheduled to start on his end of the project in 2 weekends. So we thought we could finish it the next weekend. Well, he came in during the week and need to access some of the plumbing and did a good bit of the demo. He left the cleanup to us (which is fine). 

So I want to MAKE sure I'm not getting charged for demo. Since this is the first time we used him I'm just trying to make sure he is what he seems which is a very knowledgeable, hardworking, honest, and good guy to have on our team.  Also, we have changed the scope of some of the work. In the beginning he did provide a detailed bid for us.

 So is it common practice or an acceptable practice to do this, would it be insulting?