manhattan42 wrote:
So just because one rips off and installs a primary layer instead of
installing a second one only does not guarantee that the job will be
surperior and justify the added cost. Especially if half the time once
the roof has been ripped it has been found that the paper and plywood
is in good condition and didn't need it in the first place.

Unless your house was built before there were building codes that
required good nailing of the sheathing, and you want to renail to
prevent the house from coming apart during the next hurricane (Florida)
or tornado (almost anywhere).

Unless you want to put down secondary waterproofing, or an ice-and-water
shield layer.