As shingles blow off of my aging roof in high wind storms, I'm preparing to
have someone install a new roof...
Given that it's cheaper to just lay a new layer on top of the old, what are
the Pros and Cons of laying roof down on top of the old, versus stripping
the old layer off first?
Cheaper in the long run maybe, but sooner or later you or someone else will
have to strip the roof back, as most areas won't allow more than one old
layer of roofing. Next roof job you will for sure have to strip, and you
will have twice as much debris to dispose of. Over time, this will only get
more expensive. Plus, you will get a look at your roof boards, and can see
if how good of shape they are. You may have some rotting. Better to catch
that now that hide it for another decade or two.
Unless you are planning on selling in the next few years, I'd do it right
the first time.
I suggest you look at the info on the roofing material and
consult your local building code people. Roofing over the
original roofing is certainly approved in many places, in
fact, roofing over it twice may be acceptable. The primary
problem is the weight of the material and after 3 layers you
may exceed the weight capability of the roof.
You don't need to take the original layer off to tell the
condition of the roof sheathing. If it gives a lot walking
on it, it needs replacement. A little flex is of no
concern. If the sheathing is rotting (why would it rot if
the roof doesn't leak and their is adequate ventilation?)
you will certainly know it when you walk across it.
Deterioration, not necessarily rotting, is the main
concern. Roof sheating commonly lasts for 50 years. It's
all those holes from reroofing that ruins the sheathing.
On Sun, 16 Nov 2003 01:22:16 GMT, "George E. Cawthon"
Yes. In New York, effective January 2003 (just this year), the state
requires that no more than two layers of roofing material be allowed
on a roof. This meant that I had to strip off all three old roofs
from my 1930s house before I could reroof with new sheathing
(decking), felt, ice and water shield, and 30-year architectural
shingles. But that's ok because I would have done so anyway just to
make sure I had a sound safe roof.
Bull! Think about where the heat come from and how an
additional layer cause more heat? Do the manufactures of
roofing materials decrease the guaranteed life if applied
over an existing roof? It says other things about the
gurantee on my roofing packages, but it doesn't say that.
- Nehmo -
If there is only one layer  of shingles currently on the roof.
If the existing job was reasonably well done - proper exposure, straight
If there are only a few shingles missing.
If the existing shingles aren't curled.
Then re-roof. Use the butt-up method.
Re-roofing is easier, safer, takes less time, and makes for less risk if
rain catches you during the job. And, of course, re-roofing is
substantially cheaper. In this situation, "cheaper" doesn't equate to
 All codes that I've looked at allow three layers.
********************* Nehmo Sergheyev *********************
It all depends on your budget. If you have lots of extra cash then rip off
the old and have a new roof installed. If you're on a budget and the old
rood didn't leak then you can go ahead and re-roof. I know lots of people
with two layers of roof with no problems. If your old roof is curling up
then you may have a problem. Also, if you walk around the roof and there
are many spongy areas then you will have to rip off the old. I piad 1,500
for a new roof - if I had to have the old roof ripped off the new roof would
have been double the price I paid.
Thanks for all the replies. I guess it's left to me to determine whether or
not it's worth it to increase the cost just to get a look at how things are
underneath. We don't have any leaks, but we do have some ants in the
summer. I'll see how much the guy wants and then go from there. Thanks
Large ants in the attic? May be carpenter ants, which are a pretty sure
sign of damaged wood. I like doing things right - especially when it
involves someone else's money :o) Bite the bullet, tear off the old
roof, put the new one on right and then relax for the next 20 years, or
so. Get a termite inspection done while you're at it. If shingles are
blowing off, you are overdue to get a new roof. Ask a couple of
neighbors, with the best looking older roofs, for product and contractor
referrals. Good luck.
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