Pro panel over

hey all just a question I was curious about
I have noticed in my neiborhood there have been
a few homes that are getting metal pro-panel roofs
but the thing that im curious about is that they
(the homeowner) are installing it right over the
3 tab shingles no deck prep whatsoever will there be any problems in the long run by doing this? the finished roof does look really nice after its complete but it just seems wrong to me But, I dont know Im not a pro. thanks for the replys

I don’t know why anybody would want to do that(save a little money?)We always tear off,the big thing(IMO)is putting down new underlayment,you could have condensation issues leaving the old roof in place.To me its like putting perfume on a pig.I might do it on a barn,storage shed,etc…Never on a house.

while it is not optimum, these systems are usually designed to go over existing shingle roofs.
It is a selling point…

Now i have found that some panels are not thick enough to be applyed over shingle do to the expansion and contraction the abrasiveness of the shingles wears through the panels.

ive got several metal over shingle
roofs installed 10 + yrs old, doin just fine.

the shingles are not going to scratch there way throoug the metal.