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Old 10-15-2008, 11:36 AM   #1
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Installing over Existing Shingled Roof


Recently purchased a home that was built in 1991 and has non-architectural shingles on it. The roof is in need of replacement as it is very dry, brittle and has no stones left on the majority of the roof. I would like to hire someone to install over the existing roof with a 30 year architectural shingle. Is this possible? There are no leaks, so is there any downside to not ripping up the original layer? I am trying to keep the costs down and would rather pay for a better quality architectural to go over the existing.

Would welcome some advice from the experts. Also, are there any brands that are better than others? Brands to avoid? Lastly I know that color is subjective, however are there particular one that retain the color better and resist staining, etc or should I remain with black.

THanks all!

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Old 10-15-2008, 04:28 PM   #2
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Installing over Existing Shingled Roof


If the roof is a brittle as you describe there's no way I'd ever consider layering, I don't like to to begin with...but especially if the first layer is as bad as you describe.

GAF makes good shingles, not so much of a fan of Owens Corning...I would make sure you get and use algae resistant shingles, and if you have black shingles on an inadequately ventilated roof, that could be part of the reason the shingles are so brittle. I prefer a color commonly called driftwood in the archy's kind of a gray with brown tones goes with almost all exterior colors.

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Old 10-16-2008, 06:16 AM   #3
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Installing over Existing Shingled Roof


I agree with rippy,
if the deteriation is that far advanced you should tear the old off for both cosmetic and quality reasons.

I use Gaf/Elk, Tamko, OC, Atlas and occasionally Certainteed and IKO.
Driftwood and Weatherwood are the two most commonly used colors in my area.
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Old 10-16-2008, 08:04 AM   #4
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Installing over Existing Shingled Roof


Thanks for the feedback guys - I will check out the brands and colors you recommend. As for the current roof, thats a bummer as I was really hoping to keep the costs down and layer. However, I do not want to compromise the structure of the new roof. I did have a couple of installer here, and they both thought that layering would not be a problem, I just thought I would do my own research first. One point I would like to make if it makes a difference. The only brittle shingles that I can tell are those that are on the first course on the edge. For instance, if I lay a ladder up against them, they cracked and broke - I don't see that on other areas of the roof - just worn down with little to no rocks left on the shingles
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Old 10-16-2008, 03:49 PM   #5
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Installing over Existing Shingled Roof


They aren't telling you you can't go over the old shingles, we just don't like doing it. It's always best to start with a clean slate. I highly recommend you try to get an idea if the contractor is knowledgeable in proper roof ventilation
as this is a critical factor in the longevity and performance of your roof as well as comfort and savings in your house.

As far as algae resistant shingles go, we don't even know where you are at and AR's only work in some areas of the country so a blanket "use AR shingles" is not always correct. They don't do much good around here so they are not sold much around here. Other areas of the country, they are a very good idea.
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Old 10-17-2008, 09:03 AM   #6
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Installing over Existing Shingled Roof


I would do this. If you want to do a second layer then go with a 25 year shingle. Something cheap. If you want to go 30 year then rip off. I like tamko heritage 30 ar color natural timber or Certainteed landmark 30 ar mission brown. If your looking for a brown roof. Also Tamko aged wood. GAF timberlines come in 3 place with me. I like Certainteed landmark #1 Tamko Heritage #2 and gaf timberline #3

Last edited by 747; 10-17-2008 at 09:06 AM.
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Old 10-17-2008, 10:28 AM   #7
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Installing over Existing Shingled Roof


Thanks again for the feedback - I'm in NY so I am not sure if the Algae resistant shingles are necessary, although the existing shingles look somewhat stained. I'm not sure if I will be in the house 20 years from now, therefore I am somewhat resistant to to strip the existing roof - my guess is that we will move prior to then so why incur the cost now? In addition to the roof vent I have also recently installed 4 gable vents to ensure proper attic ventilation.
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Old 10-18-2008, 09:10 AM   #8
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Installing over Existing Shingled Roof


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Thanks again for the feedback - I'm in NY so I am not sure if the Algae resistant shingles are necessary, although the existing shingles look somewhat stained. I'm not sure if I will be in the house 20 years from now, therefore I am somewhat resistant to to strip the existing roof - my guess is that we will move prior to then so why incur the cost now? In addition to the roof vent I have also recently installed 4 gable vents to ensure proper attic ventilation.

Wow ny they will kill you on roofing prices over there. Big difference from illinois. Well not kill but much more expensive then ed would do it for here in Illinois.
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Old 11-15-2008, 06:13 AM   #9
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Installing over Existing Shingled Roof


The 40 year old "20 year" shingles on my mother's 2 car dettached garage are puckered, moldy, and some are broken. Now, after reading this thread, it is clear to me that I should strip the first layer and redo the roof from scratch. My question is.... what are the consequenses if I power wash off the mold, cut out the puckers, and "fill in" the broken/missing tabs before I put the second layer on? I ask this so I can explain to mom why it's a good idea to strip the first layer. Thank you in advance for your help.
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Old 11-15-2008, 06:23 AM   #10
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Installing over Existing Shingled Roof


with all that prep work, wouldn't be better to strip the old and install the new???. Time wise?
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Old 11-15-2008, 09:05 AM   #11
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Installing over Existing Shingled Roof


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The 40 year old "20 year" shingles on my mother's 2 car dettached garage are puckered, moldy, and some are broken. Now, after reading this thread, it is clear to me that I should strip the first layer and redo the roof from scratch. My question is.... what are the consequenses if I power wash off the mold, cut out the puckers, and "fill in" the broken/missing tabs before I put the second layer on? I ask this so I can explain to mom why it's a good idea to strip the first layer. Thank you in advance for your help.
Like Buletbob said, by the time you went through all that trouble, you'd already have the old stripped off and the deck prepped for the new roof. One layer of old three tab is a pretty easy tearoff.
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Old 11-15-2008, 06:18 PM   #12
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Installing over Existing Shingled Roof


If you do what we call a Tab Cut you wouldn't need to power wash anything.
Cut every single tab off each shingle through out the entire roof,
cut all rakes and eaves back even to the roof deck,
remove all ridge caps,
sweep well,
check metal flashings along walls and chimneys, if not rusted, ripped or out of place you probably can re use them,
install new drip edge on eaves and rakes,
install new shingles,
re-place all plumbing stack covers, ventilation units, etc.


After all is said an done, you utilized the same amount of time as a re-roof,
and saved in the area of 20% of the cost.

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