Has the same manufacturer s warranty.
How to install a roof over existing shingles.
Some roofers install a layer of waterproof shingle underlayment wsu over the existing shingles at the eave end as would be done for a roof laid on bare sheathing.
Looks just as good and lasts as long.
This provides added protection against ice dams.
As long as it s done right and under the right conditions installing new shingles over old ones can last as long and look just as good as a complete re roof.