Roof Replacement (Capex) vs. 1/2 Roof Replacement (Opex)?

[Jim Young]

The roof on my townhouse is nearing the end of it's useful life.  The ridge cap recently blew off and I'm facing the old "repair or replace" question - with a twist.  It's a simple peaked roof.  The front slope faces SW and is exposed to the sun.  I could replace it right now and feel good about it.  The back slope is more protected and has more life left.  I don't feel so good about replacing it right now.  A roofing contractor suggested something I'd never heard of: just replace the front half.  He said that way it would be considered a "repair" and could be expensed as opposed to replacing the whole thing which would be a capex and would have to be depreciated, not expensed.  Does that make sense?  Have any of you done that?  Thanks!