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Reroofing by installing new shingles over old shingles

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[OP]
Deal Guru
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Feb 23, 2008
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Brampton

Reroofing by installing new shingles over old shingles

Anyone re-roofed by installing new shingles on top of the old shingles? Looks like this is a cheaper way to re-roof your home and it's just as good. Perhaps this can even be a DIY job? Could save a heck of a lot of money by doing it yourself.

IKO reroofing over existing shingle roof...
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23 replies
Deal Expert
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Jun 12, 2007
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London
No, don't do this. This is one of those things were you *could* do, but maybe not *should* do. The only time you should ever do this is for a house you are about to flip.

You should pull off all the old shingles and check the wood on the roof deck for problems. It's easy/cheap to fix the roof deck when all the shingles are off and replace any bad wood.

If there's any problems with the deck, covering over the old shingles/ wood rot with new singles doesn't magically fix the problem. All that will happen is you will eventually have to pull both the new and the old shingles off, fix the problem, then re-single with yet again.

Also, any disposal costs that you would have saved for the old shingles, you'll eventually have to pay down the road at the next re-roofing. It's like kicking the can down the road. The costs to remove/ dispose of 2 layers of shingles is more than just 1 layer.
Deal Addict
Feb 26, 2016
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Vaughan
from my understanding, you only do this with metal roofs.
Deal Addict
Nov 17, 2012
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Toronto
How does re-roofing make this more DIY than a proper roofing job? If anything, it would be more challenging to put new shingles over old than the simply brute force labor to remove the old roofing and then roof over a nice smooth uniform surface.

I'd never put new over old anything - flooring, drywall, siding, roofing... always strip it down as far as possible and build up new again. Just had Coverall Roofing out to do some flat, shingle, siding and soffit/fascia work. Stripped everything down to the 110 year old original surfaces.
Member
May 12, 2003
371 posts
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GTA
OP, the consensus generally is that you should remove old shingles, inspect for any pre-existing damage, fix damage, and install new shingles.

Without removing the previous shingles, you may just be hiding issues.
[OP]
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Feb 23, 2008
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Brampton
torontotim wrote: How does re-roofing make this more DIY than a proper roofing job? If anything, it would be more challenging to put new shingles over old than the simply brute force labor to remove the old roofing and then roof over a nice smooth uniform surface.

I'd never put new over old anything - flooring, drywall, siding, roofing... always strip it down as far as possible and build up new again. Just had Coverall Roofing out to do some flat, shingle, siding and soffit/fascia work. Stripped everything down to the 110 Year Old original surfaces.
After 110 years have passed there would definitely be needed inspection of the roof boards for rotten sections. But for a newer home 20-30 years old there should be less issues with the roof. Gutters, facia, soffits should still be in good condition. Vents probably could take replacement. I also don't see why it would be difficult to nail new shingles on top of the old ones, unless the old shingles were curled then re-roofing would not work.
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Deal Addict
Nov 17, 2012
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Toronto
IKO's page basically says if the old shingles are in great shape, not curled, not leaking etc, you can go over them with new shingles.

Naturally that begs the question of why you'd be re-roofing at all. They suggest if you want a fresh look, like it's getting a haircut or something.

Remove and replace.

I had Coverall remove my 15 year old shingles on the garage because they were curling on one side (south facing). I covered the entire roof with ice membrane when I did the shingles myself back then, so it wasn't leaking and could have been left, but they looked like crap. Paid $1300 to do the 12x20 garage along with the other work already being done. Money well spent considering how much it would have cost me to DIY at some point in the future.

The only time I'd consider going over shingles is with a metal roof, but even then, the shingles would have to be in great condition and a large job to warrant not spending the extra $$$ to peel it down to the sheathing and put fresh membrane down under the metal roof.
Deal Addict
Nov 17, 2012
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cheapmeister wrote: After 110 years have passed there would definitely be needed inspection of the roof boards for rotten sections. But for a newer home 20-30 years old there should be less issues with the roof. Gutters, facia, soffits should still be in good condition. Vents probably could take replacement. I also don't see why it would be difficult to nail new shingles on top of the old ones, unless the old shingles were curled then re-roofing would not work.
Just saying from a DIY perspective there's no difference in difficulty.
Deal Fanatic
Nov 21, 2013
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Like said, you are hiding potential issues with the deck, and, above this you add weight. Taking into consideration that a roof shingle pack can weight +- 70 lbs, leaving old shingles add weight to the structure.

Now, removing the old shingles is not more DIY. It is easier to remove old shingles with preper tools than install the new ones
[OP]
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Feb 23, 2008
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Brampton
DoorCrasher wrote: Like said, you are hiding potential issues with the deck, and, above this you add weight. Taking into consideration that a roof shingle pack can weight +- 70 lbs, leaving old shingles add weight to the structure.

Now, removing the old shingles is not more DIY. It is easier to remove old shingles with preper tools than install the new ones
I agree with the weight being an issue. But I also read that a roof can be re-roofed 2 additional times. So the maximum allowed is 3 layers of shingles.
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Deal Fanatic
Apr 11, 2006
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Mississauga
cheapmeister wrote: I agree with the weight being an issue. But I also read that a roof can be re-roofed 2 additional times. So the maximum allowed is 3 layers of shingles.
Three layers?!?! That is insane. Can and able, doesn't mean should. You never know how well the previous install was done. There could have been some water leaking under the old shingles somewhere.

Mistakes happen. Bad jobs are a reality. Rip it off and replace.
Deal Guru
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Mar 13, 2004
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2 Layers max is what I would say. The older homes with stronger roof structure can take 3 layers as they would be using bigger pieces of would like a 2x8 or bigger. Where the newer homes might be 2x4 or 2x6. But either way I would not put more then 2 layers because you also have to factor in the weight of snow/ice in the winter.

But as others have said its always best to remove everything this way if the wood is rotted or if there is a slight leak you will be able to find it and repair because it does major damage.
cheapmeister wrote: I agree with the weight being an issue. But I also read that a roof can be re-roofed 2 additional times. So the maximum allowed is 3 layers of shingles.
0_o
<_<
>_>
Deal Fanatic
Oct 6, 2007
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Kootenays
In our area where UV is very strong (2,000 hrs of sunshine/year) multi layers of shingles is common. When we had our roof done, 3 layers came off. The house was built in 1964. We are the second owners, having bought in '92, so the previous owners reroofed every 10 years. We did the roof around 2005 and stripped to the shiplap 1 x 6. Iko required us to sheet everything over the shiplap to maintain warranty. Although I choked on the $17,000 price tag, the roof still looks brand new to this day.
[OP]
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Feb 23, 2008
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smacd wrote: In our area where UV is very strong (2,000 hrs of sunshine/year) multi layers of shingles is common. When we had our roof done, 3 layers came off. The house was built in 1964. We are the second owners, having bought in '92, so the previous owners reroofed every 10 years. We did the roof around 2005 and stripped to the shiplap 1 x 6. Iko required us to sheet everything over the shiplap to maintain warranty. Although I choked on the $17,000 price tag, the roof still looks brand new to this day.
Were you charged more because the 3 layers of shingles needed to be removed?
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Deal Addict
Nov 17, 2012
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Toronto
cheapmeister wrote: Were you charged more because the 3 layers of shingles needed to be removed?
The full layer of plywood is likely where a good chunk of money went.
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Oct 6, 2007
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cheapmeister wrote: Were you charged more because the 3 layers of shingles needed to be removed?
It wasn't broken down by individual costs, but certainly I paid for the labour involved and for the removal charge of the dumpster.
Penalty Box
Jun 24, 2015
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i would not do it, you could be shingling over rotten wood and not even know it

the house is one of your biggest expenses would you risk something like this? probably not, and should not
Hi
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Nov 3, 2008
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Like others have said I would worry about loading on the roof. Two layers of shingle plus a heavy snowfall....might not be a good idea?
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Feb 25, 2004
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Longueuil
Weight would also be my main concern.
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Dec 13, 2008
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Hamilton
Go to the lumber store and try to physically pick up a bundle of shingles and you will have you answer. The added weight will stress you roof structure and may actually make it sag.

Speaking from experience, this was done on the common roof between my townhouse and my neighbour.. After two years the roof is visibly sagging and I have already paid to repair a leak.

My advice, strip it, fix what's needed and say good night.

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