On Mon, 23 Jun 2008 04:12:53 -0700 (PDT), Ben
wrote:

:I moved into my house not too long ago and had the first occasion to
:want to go up to the roof yesterday. It looks like there are three
:layers of shingles. I've read that you should never have more than
:two layers of shingles because of the weight. How much should I worry
:about this?
:
:Thanks for your input,
:-Ben

My understanding is that 3 layers is maximum, i.e. if a roof with 3
layers needs reroofing, a complete tearoff is the first step. This is
what happened when my roof was redone around 3 years ago. Judging from
this thread, many if not most areas now require no more than 2 layers.
As noted, make sure about your assessment of how many layers are on
there.

Dan