John Willis Wrote:


So far as I know, National Building Codes allow up to three roofs on a
house. Just because it is up to code does not mean it is ideal. A
house with more than one roof installed is more likely to develop
leaks (because the roof exposed to the weather is not installed over a
uniformly smooth substrate) and I've never seen a second roof like
this last as long as it should. In every case I've seen, a house with
a second, third (or more) roofs installed require attention far sooner
than they would if there had been only one roof.

But that is not the observed fact by shingle manufacturers nor the Code
agencies. There is no more lilkelihood that a covered roof will fail
prematurely than one over a fresh substrate all things being equal.

Which is why manufacturers offer FULL warranty of their products and
Code Officials allow the practice.

Likewise, I have NEVER seen a second layer fail prematurely in my 25+
years as a professional contractor simply because it was a second or
third layer.
If they failed, it was due to issues completely unrelated to the number
of shingles.

So just because one rips off and installs a primary layer instead of
installing a second one only does not guarantee that the job will be
surperior and justify the added cost. Especially if half the time once
the roof has been ripped it has been found that the paper and plywood
is in good condition and didn't need it in the first place.

Yes, the issue is money, and more often than not it is money the
contractor wants to needlessly put in his own pocket at the expense of
a gullible homeowner.


--
manhattan42
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