BETA-2K wrote:
I am about to have a new asphalt shingle roof put on my house. It now has
one asphalt shingle roof on it and the decking underneath is in good shape.

Other than it costing a little less by saving on the tear-off process, is
there any real difference between ending up with one roof or two?

Even if it costs more, if there is an advantage to having the present roof
taken off first, I would do that.

So long as the old roof is just ageing and not having problems with
quailty, then the gains to be made with a tear off simply aren't worth it.
Go ahead and apply a second layer of shingles, there will be a very small
decrease in the life of the second set but that will be more than ofset by
the saving in istallation.

But if the fisrt layer of shingles is failing due to poor istalation or
damage or somthing like that, then ext layer will also suffer from those
things and fail prematurely: in that case you really ought to tear it off.


John
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