This is a complex subject and the details may change based on the client’s needs. We will always transfer ownership of trademark design (logos, wordmarks, etc.). Generally for the rest of our design work we provide a pretty broad license. The client can pretty much do whatever they want with the final artwork, but we don’t deliver unused designs, rough work, or transfer artwork ownership unless the client has a really good reason and the budget to allow for it. Licensing (instead of transferring) artwork protects us from some rare (but harmful) scenarios while still allowing the client to do everything they need.
FYI
Cast Iron Design is now The Office of Ordinary Things. We relocated from Boulder to San Francisco, but otherwise we’re pretty much the same people doing the same things, just a bit more hardcore.