Question from experienced rehabbers about roofs

[Stephen N.]

I am about to start a project on a house and my contractor says that instead of replacing the current roof he can do a "nail over" of new shingles on top of old.

have you ever done this? is there a problem with doing this?

[J Scott]

Multiple layers of shingles are very heavy and can cause structural issues with roof framing and structures. A decent home inspector will catch this, identify it to his client, and you'll have a buyer who is wondering where else you may have cut corners...