On Mon, 23 Jun 2008 16:14:05 -0400, Phisherman wrote:

:Having just one and only one layer is best. Shingles are heavy and
:can put extra stress on a roof. I've seen some really bad sagging
:roofs with 2,3 and 4 layers of shingles on it.

My roof was a sad sagger before the complete tearoff of the 3 layers
that were on there around 3 years ago. It's amazing how nice it looks
now. All that sag is gone.

Dan