quote:

Originally posted by Oz_Shadow:
1 layer? You may be able to save some by skipping the tear off if so.

Not a great idea! Leave the underlying shingles in place, increasing the thermal mass absorbing and retaining radiant energy and transmitting it to the structural members, should be really good for longevity. Also, any moisture within the structure (such as residual moisture from bathing, cooking, or breathing) has a good place to collect, then expand and contract with temperature changes, further infiltrating the structural members and providing a good source of oxidation and corrosion for your new metal roofing.

Also, research your new roofing materials warranty, learn what the manufacturer requires for installation in order to qualify for that warranty (tear-off, underlayments, flashings, etc). Failure to follow manufacturer's specifications means NO WARRANTY AT ALL.

If you’re selling the place, why even bother with replacing the roof? Just patch to get you through the next two years and let that be the new owner’s issue to deal with.

Doesn't really apply to this situation but a properly installed painted, or bare with acrylic, Galvalume metal roof will outlast the vast majority of the members on this forum.

^^^^
That is why I am considering one. A house down the street from my parents is pushing 45 years and it still looks nice.