AndrewJ wrote in message . ..

Thanks in advance, Jeff R.

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We are in the Midwest.
Believe the existing shingles are asphalt organic felt (does this matter?

No.

Some of the existing shingles have started to curl slightly.

Should be ok if you choose a dimensional(cedar look) shingle.

Guys putting up cheap shingles must do a tear off. Poor quality
shingles look awful going over anything but sheathing. We put 30 year
shingles over decent roofs all the time. It's called a "roof over" and
exact directions are on every bundle sold. 99% of the country allows
upto three layers of shingles with some regions allowing four.

The second part of the scam is that the lowest bidder saying a tear
off is needed, always "happens" to find a lot of damage. Possibly
charging $100 or more a sheet to replace the sheathing. Only when
everything is said and done do you realize they were actually the
highest bidder.

This question comes up every few months. Just Google it for
essentially the same responses as above. There is always somebody who
will put layer after layer on and swear by it. The truth is that the
50% longevity of a "roof over" is often the case. Plus, the appearance
is often not as good. And the cost of the next replacement when it
does come will be higher.