Most of the time, a reroof can be completed even without having to replace any of the flashing. Nevertheless, you can always take this opportunity to install more efficient flashing, such as the drip-edge type, for a further reinforced roof structure. Ask Palo Alto, CA roofing contractors whether this would be a practical move for you.
While a reroofing job is generally more cost-efficient than a tear-off replacement, inspecting your old shingles before placing new ones over them is still necessary. After all, you wouldn’t want your roof destroyed from the inside, would you?