In alt.home.repair
Seeker wrote:

I have a twenty-two year old home. I am assuming that the builder
quality shingles used in construction of the house mean I should be
looking at a new roof...soon!

This will be the first roof I have ever replaced. One company,
check-rated in the local consumer guide, came and gave me an estimate
for reshingling over the old roof.

Another company, with a good reputation but not check-rated in the
same guide, said they would not re-roof over an old roof and gave me
what sounded like reasonable reasons for so arguing.

Leaves me up in the air: two seemingly good companies, one saying
reshingle, the other saying don't.

What's the common wisdom on this? Reshingle or tear up the old
shingles and do a new roof?

Bob,

It is "acceptable" to reroof over old shingles but not recommended. In no
time it will look lumpy. It will also not last as long and may cost you
more on insurance.

When I bought my home, I had asphalt over cedar shingles. Allstate wanted
a 30% additional premium for it. Others wouldn't even insure it at all.
And, when you replace it again, it will cost more to remove 2 layers. And
you will replace it sooner because the shingles can't dissipate heat as
well. It may also void your warranty.