Should I replace all old DWV stacks through the roof before re-roofing? I would think so.
Only if needed.
Are they PVC or Iron?
Unless they are ABS and already sticking up 6" or so
No need to replace, but I would put new lead boots on.
I would verify the integrity of the entire stack down to it’s lowest point. If ANY part of the system appears to be needing repairs within the next few years, be proactive and replace it!
That is one example of the difference between a home that sells fast for max. $$, and a pos that sits abandoned that nobody wants… i.e. the care and maintenance of the home.
So true. As you know, make sure it is done right.