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Old 02-12-2010, 09:18 AM   #1
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2 layers on house


We have 2 roofing layers on house. The roofer that came by to look at ice dam leakage told me that having more than 1 layer is bad because the roof cant dry out properly and shortens the roof life by a number of years. That was the very first time I had heard that about multiple layers.

Can any roofers out there give me the skinny on that please. Is this true? If so, then why would any municipalities even allow a 2nd layer? Or why would any roofing manufacturers offer warranties on a second layer?

Our roof was put on in 2002(we bought house last year) and the roofer said we would only get a couple more years out of it before it needed replacement. ????? Sounds like he was trying to sell me a new roof before I needed one unless what he was saying was true about it shortening the roof life

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Old 02-12-2010, 02:37 PM   #2
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2 layers on house


I am an advocate of always tearing off a sloped roofing system. The reasons for this are numerous which I will discuss. I have done 1 shingle lay over since I started my business in 2003. I have done maybe 5 in my entire career since 1998. I beleive in quality and I do not beleive that a lay over is quality.

I agree with your roofer, but not necessarily for his reasons. In theory the original layer should not be getting wet so why would it need drying out? But I will tell you that the 1st layer does continually corrode beneath the top new layer which affect the look of the top layer over time. In addition weight is sometimes a concern, although not a major concern. My biggest concern is proper underlayments like an ice and water shield. You can not install ice shield without at last tearing up sections of the roof, and if you are tearing up sections why not tear it all up. In addition I am concerned with any wood substrate that may be rotten or damaged in any way. These thigns affect my personal guarantee, so I can't really give a good guarantee when going over.

I'll add that most commonly a lay over is nothing more than shingles over shingles. A roof is a system that is made up of not just shingles, but underlayments, flashing and ventilation. Yes the flashing and ventilation can be addressed in a lay over but usually it's not. Usually it's just shingles over shingles. Cheap.

A few villages and suburbs around the chicago area have begun to limit the number of layers to one. Infact the city of Chicago used to allow 3, but came to their senses and reduced that number to 2.


If the roof was put on in 2002 why do you need a new roof now? Sounds like someone made some mistakes in 2002. Even the worst shingles usually last longer than 9 years. Are you saying you had a lay over in 2002? I would not expect more than 15 years out of a lay over on average. I've seen them last longer, but usually am ripping them up 15 years after they were done.

The last thing I'll leave you with is many shingle manufacturers have reductions in their warranty and exclusions in their warranty when laying-over.

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Old 02-12-2010, 04:34 PM   #3
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2 layers on house


The acceptance by the public of roof overs varies from region to region.
In FL it is allowed by code, but not many reputable roofing companies will do it. Grumpy gave some good reasons above why not. For the sun belt I would add the top layers life is shortened by it not disapating heat as effectively do to the added insulating value of the rotting layer below. Also as the bottom layer rots away how tight will the nails on the top layer be ? Nail pops, lose shinlges, wind damage in a slight breeze anyone?
Why install a 20 yr shingle and be very lucky to get 12 or 15 years of shingle life?

LOL... I know in Denver '90 (hail storm took 3/4 of the roofs in the city) the sod house mentality rulled... the more layers the better... (Free Insulation) I saw pleanty of old rag paper or what was left of it.. on the older houses.
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Old 02-12-2010, 04:54 PM   #4
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2 layers on house


Bob I agree with what you said. I want to point out that the idea that the roof offers any useful insulation value is a huge crock of misinformation floating around the internet. If the attic is properly ventilated then the shingles will not retain any heat. I do agree though that the entire roofing system will propbably likely increase in heat, but not the attic space. The attic space is typically designed to be ventilated on the top and insulated on the bottom.

I just wanted to point that out, because there is at least one roofing company in the area that promotes lay overs on the basis that the extra layer of shingles adds insulation. I want to punch them all in the face!
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Old 02-12-2010, 05:57 PM   #5
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Grumpy, we are on the same page.. thank you for debugging the roof over "insulation" myth.

I think in Denver the HO's would compare how thick the snow was on their roofs... the guy with the most snow on top could say "see what a well insulated house I have!" The neighbors could hardly wait to add another layer of shingles..LOL
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Old 02-12-2010, 05:57 PM   #6
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Just to add onto what was already said - I have always been under the impression the shingle manufacturer companies arent fully against a second layer is because they know some people just cant afford a full tear off and they still want to sell their product. Of all the two layer roofs I have torn off, I have seen ONE done properly. Majoroity of the time, as Grumpy said, majority of the issues are not properly addressed or resolved.

I am a firm believer that a second layer will reduce the life of the shingle. Ive torn off two roofs that were both less than 10 years old that have two layers. I dont think the roofer you had come take a look was BSing you at all.
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Old 02-12-2010, 08:57 PM   #7
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I agree that a tear off is the best way to go and I always let the home owner know that, proof of that is since i started Fox Roofing in 1994 I have only done a half dozen or so lay-overs and maybe a few dozen all together since I started roofing in 1979, but I disagree with the roofers who say you can't because they don't work and/or won't last.
All of the lay overs I have done since 1994 are still intact and problem free including the home I live in, I did a lay over on it in 1989/90.

I have torn off roofs in which the second "top" layer was 20 plus years old, which is not a bad life span for a 25 year 3-tab shingle on a walkable roof, I have seen them as old as 24 years on steeper roofs.

If your roof fails prematurely it's either faulty material, poor workmanship or above normal storm damage.

With all that said, the only way you can get moisture between the two layers is if the top layer is leaking, if you stop the top layer from leaking the moisture will no longer get between the two layers and there won't be anything to try out.
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Old 02-12-2010, 09:05 PM   #8
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Quote:
Originally Posted by Grumpy View Post
A few villages and suburbs around the chicago area have begun to limit the number of layers to one.
Do you happen to know which AHJs are doing this?

Thanks.
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Old 02-12-2010, 09:09 PM   #9
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Originally Posted by BamBamm5144 View Post
Just to add onto what was already said - I have always been under the impression the shingle manufacturer companies arent fully against a second layer is because they know some people just cant afford a full tear off and they still want to sell their product. Of all the two layer roofs I have torn off, I have seen ONE done properly. Majoroity of the time, as Grumpy said, majority of the issues are not properly addressed or resolved.

I am a firm believer that a second layer will reduce the life of the shingle. Ive torn off two roofs that were both less than 10 years old that have two layers. I dont think the roofer you had come take a look was BSing you at all.
If you read/listen to what roofers say when they talk about lay overs and why they do not work you'll notice that every thing they mention is a result of poor workmanship.
1. They did not core sample the existing roof, thus they layed over bad sheathing or re-used bad flashing's.
2. They layed over an existing shingle that was into poor of condition and the new never laid properly.
3. The roof was not vented properly so the attic/crawl space held in even more heat due to the second layer.
Etc, etc,etc.

Poor workmanship used on a lay over, re-roof or new construction will end in premature failure, good workmanship will end with a roofing system that will last it's expected life span.
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Old 02-13-2010, 09:32 AM   #10
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Sly - I agree. However, majority of roofers who do not do a full tear off, do not replace all those things. I know it is usually poor workmanship. I know that a second layer can last an incredibly long time. This year I tore off one which was done properly and I thought it was only one layer until I actually got going on it.

I guess my point being this, How many roofers do you know will take all those steps in order to do a lay-over? My assumption has always been that the majority of them that are too lazy to do a tear off, are too lazy to do things the correct way. As a matter of fact, there is a company here that pushes doing lay-overs. They only started about two years ago, so we will see how long that lasts.
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Old 02-13-2010, 03:08 PM   #11
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It's not legal anymore to do a second layer in the "hail zone". I'm sure Wisconsin is included. I wonder how that company gets away with it. Maybe there are no permits and no inspections.
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Old 02-13-2010, 03:53 PM   #12
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MJW, only a few cities need permits and they are rarely ever pulled. Inspections then arent given and so the cycle continues. I never knew they promoted this until seeing thier ad on the good ol CL each and every day.
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Old 02-13-2010, 04:34 PM   #13
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Quote:
Originally Posted by BamBamm5144 View Post
Sly - I agree. However, majority of roofers who do not do a full tear off, do not replace all those things. I know it is usually poor workmanship. I know that a second layer can last an incredibly long time. This year I tore off one which was done properly and I thought it was only one layer until I actually got going on it.

I guess my point being this, How many roofers do you know will take all those steps in order to do a lay-over? My assumption has always been that the majority of them that are too lazy to do a tear off, are too lazy to do things the correct way. As a matter of fact, there is a company here that pushes doing lay-overs. They only started about two years ago, so we will see how long that lasts.

I agree 100% when you say most roofers will not take the time to do it correctly, many roofers simply do not know how.

I was just wanted to let the home owner in this post know that lay overs can be installed to last so he don't think getting a new roof is the only way to solve his current problems.
He very well may need a new roof, I do not know, maybe with pictures I could give a better educated guess, but it would still be an opinion not fact.
Now that he knows lay overs are possible, he can call another roofer in the hopes of finding a more experienced one that will be able to offer him repair options.
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Old 02-13-2010, 10:51 PM   #14
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Do you happen to know which AHJs are doing this?

Thanks.

Your pic looks familiar. Youre on inspection news arent you?
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Old 02-14-2010, 10:13 AM   #15
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Another thing to consider is with a second layer, you may save a little now, but you will definitely pay much more later. "later" may come sooner than you think.

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