Re-Roofing (R907)
New roofing may be installed over an existing roof but is limited to a total of two layers.
Existing flashing in good condition can be reinstalled. Any sheathing that is replaced must be installed per code.
In all cases, the roof structure must be capable of supporting the roof covering system and any loads that will be encountered during the installation of the new roof.
Roof Edging
Roof edging is not required by the code. Some manufacturers may require it.