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.
Where do you live? Does it get below freezing in the winter much?
I'm in nothern Illinois, USA. One reason I did a tear off vs nailover
was to get the iceguard sheeting that provides a lot better protection
against ice damming than otherwise. It's code here now, but wasn't
done on roofs 10 years ago. Another reason is that there were some
small signs of water penetration on the house when we purchsed it, and
given I wanna stay here awhile, I wanted to make certain there was no
rotting or anything more going on with the roof decking.
There are other modest advantages to a tear off which are hard to
quantify. One of which is that you'll have a lot less weight on your
roof. Not a big deal, it's surely designed to hold it though. The
second is that the new shingles are working on a much flatter surface,
so they'll look better in the case where you have any curling
occurring on your first layer. Finally additional layers can harbor
additional moisture. Whether either of these "soft" peace of mind
issues will amount to any real increased risk of water penetration
over the life of your new roof is probably debateable at best.
Personally I feel it's just technically a lot cleaner to do a tearoff.
However, if you don't plan to stay in the house very long and can put
the delta in $ to better use elsewhere, a 2nd layer isn't necessarily
a bad thing thing, though buyers may look slighly more favorably on a
tearoff vs a 2nd layer.
A couple of things to consider. How long will you be living in the house?
If you plan to retire there and live long enough to need another roof, it
may be better to pay the extra now for a tearoff than in 20 years when you
have limited income. If you plan to sell in just a few years, having a
good, new, single layer is a good selling point.
If the existing roof is in good condition and flat, you will see no
difference in the finished roof. If it is curling up, or otherwise
physically damaged, get it off.
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.
Remove the dead poet to e-mail, tho CC\'d posts are unwelcome.
Mean People Suck - It takes two deviations to get cool.
I'd probably leave it up to the roofer. Usually you do not tear off
existing shingles until 3rd roofing job because of weight. But if your
existing shingles are badly warped and you are putting on a single
colored untextured shingle, it may show through.
First, if you leave the present shingles on, there's the question of
knowing for sure there isn't a spot or two where the decking maybe
isn't as good as you think...
Second, while a lot of roofs are put on w/ two or three or even more
layers, it isn't the manufacturer's recommendation and may shorten or
limit warranties and is generally known to shorten expected life span
of the new roof.
My opinion is that you're putting on a new roof and to skimp is in the
"penny wise, pound foolish" category.
It is becoming increasingly uncommon to put multiple layers of shingles
on. Most contractors insist on a complete tear off these days and
cannot guarantee the results otherwise. I have never installed new
shingles over old but have torn off a lot of multiple layer roofs.
One advantage of a complete tear off is that the roof deck can be
inspected and repaired. It is common that the deck is rotten in
places especially where multiple layers are present. then you can
start from the deck up with a clean, dry, and sound surface.
I bet most jobs that include multiple layers these days are done by the
homeowners or family members who just want to get it over with and
don't have the time or energy to tear off and clean up all that
material. Tear off and clean up can be a much bigger job than
installing the new material. It is a huge part of getting the job done
Thanks to everyone. I thought I posted a response last night but I don't
see it here.
The short version of what I tried to post last night is that I will probably
just go ahead and have the tear-off done before the new roof goes on.
Overall, that seems like the safest bet although I can see good reasons for
doing it either way.
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