shingles over existing shingles


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Old 03-22-05, 09:29 AM
smacky
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shingles over existing shingles

Is there any leveling that has to be done when applying shingles over an existing shingle roof or may I just follow the old roof shingles.
 
  #2  
Old 03-22-05, 09:49 AM
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Wink

Just put them on is all. But I would take the old shingles off and do a good job.


ED
 
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Old 03-22-05, 03:09 PM
E
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Ed is right that it's better to strip off the old roof.

But, if you insist....check to see if the rows of shingles are straight. If they are, and you're using the same style of shingle, you could do the "But&run". I never use it cause I think it's a bit lazy, being I'm a roofer getting paid to roof, but alot of "roofers" around here do it that way. It would mean cutting back the first row of new shinglles at the drip edge, even with your drip desired line. Then just "but" each following row up to the bottom of the next old shingle.
Make sure you install a "starter" shingle at the eve edge first, regarless of the fact it already "has shingles there".
 
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Old 03-22-05, 08:25 PM
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I don't roof for a living, but I've done at least 100 roofs, and I'd like to think I do a pretty darn good job. (unlike the reputation some roofers in my area have.) So I'd like to ask E. Dodge (or Ed) a question regarding this topic.

You say that it's "a bit lazy" to do it that way. (cutting off the first row then butt and go) I guess I've always thought that was the BEST way to do it, since the shingles will lay a lot flatter that way. If you draw out on a piece of paper how the shingles lay, maybe you will see this is true. It really has nothing to do with it being a shortcut (even though it might be).

What I've observed is that if you do not cut off 2" or so on the first course, the tar strip falls in an area where the shingle is not fully supported by the underlying shingles. If the tar strip sags down into this depression, the tabs won't be sealing to it very well. The house right next door to mine was roofed this way (3 tabs) and almost every tab has lifted in the wind. It has a very wavy appearance. (My bedroom window is at eye level with it, so I get a good look at it every day.)

But if you cut off the 2" to start with, only the first row and starter course will have a funny bump- the rest will lay perfectly flat (provided the 1st layer of shingles is flat.)

I'm eager to hear your opinion on this, since you seem to be very knowledgable about roofing, and I certainly don't claim to be an authority on the subject.
 
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Old 03-23-05, 03:49 AM
E
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I can't say I have a legitimate reason for my not using the but&run" method. Unltimately it may have nothing to do with squat as to the performance of the roof.
My thing is that I've noticed a number of things over the years that guys do in roofing as "shortcuts". I've seen many of these "shortcuts" cause or contribute to leaking of some kind.
And yes, IF one uses the "but&run", one should cut off the first row even with the desired drip edge {I tried to explain that}.
I've never had a problem with shingles "sticking up" on recovers unless there was a pre-existing condition" on the roof, such as shingles which are a tad lumpy, or underlying decks which are a bit lumpy. If I feel that a slighty mis-shapen roof installation will not hurt the performace of the new roof, and the customer simply cannot pay the costs of strip-off, I'll give them what they can afford.
I just have a deep aversion to taking shortcuts for no other reason that speeding up the job.
For instance, my first roofing experience was as a laborer on huge flat roofs covering military wharehouses in Utah. One of the required "specs" was to pull every single nail out of the deck prior to roof installation. Well, once I went out on my own, I did the same thing, on ALL roofs. To this day we pull ALL the old nails/staples out of the roof deck prior to felting. EVERY other single roofer I've seen around here just pounds them down or bends them over. Does it make a functional difference on the end product? Probably not in nearly all cases. But I can't bring myself to compromise on that aspect. Same thing with new flashings. We install ALL new flashings on any roof which we've stripped. Although one might reuse all or most of the old flashings and never have a problem, I can't see trying to save one to several hundred bucks on a new roof by reusing and relying on old metal. By the way, none of the above means we're perfect, because we ain't. It's just the idea of trying to do the best possible when installing something that should work from the beggining, and offer trouble-free service for years.

As for your "100 roofs" installed, I think that can easily qualify you as a roofer. The fact you think about what you're doing with it already places you above most of the "real" roofers I've ever run into.
 
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Old 03-23-05, 10:50 AM
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Thanks for the reply. I totally agree with you regarding pulling nails. It doesn't take that much longer, and it's a nicer job. You won't catch your pants on them later, and they won't poke through the felt either. And replacing flashings too. Roofers who shingle over those old rusty galvanized flashings and valleys ought to be shot.

And why is it some roofers put d-edge along the gutter? Don't they know what gutter apron is?

I was just on a roof the other day replacing some windows, and the step shingles were all visible ON TOP of the shingles. Wonder who the genius was that did that? And then near the corner post, the flashing was lapped the wrong way (so that water would be directed UNDER the flashing).

Another roof I was on, they had totally omitted the step flashings, and installed a gutter apron upside down on top of the old shingles, then proceeded to roof right over that without using any step flashings. Needless to say, the roofer had tarred the bejesus out of it. I rarely need to use any roofing tar when I roof. There's really only very few places where it's even needed.

I've got friends who had their roof done a couple years ago (by a self-proclaimed roofing contractor and his crew of college kids who have never even been on a roof before- BTW, he's no longer in business) and their roof leaked about 5 times that summer, ruining their carpet in one room. Of course, his solution was not to tear off and repair his mistake... it was silicone and more flashings. I felt so bad for my friends.
 
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Old 03-24-05, 04:46 AM
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I can't begin to remember, and tell you, of the multitude of roofs I've seen over the years which sprung half-a-dozen leaks AFTER getting a new roof. What I'm talking about is where a customer had an old roof with no actuall leaking, then had it redone, due to age, hail storm, etc, only to get a massive pile of junk installed. I still cringe once in awhile when seeing one of these jobs, even though I had nothing to do with it.
Ultimately it's good for me, wanting more work, but bad for the homeowners...and bad for me as well because it's so prevelant out there that it paints the whole industry with suspician....for good reason.

In addition to the outright scammers, there's just a huge black hole of untrained, unsupervised guys who MIGHT take the time and knowledge in only someone would take the time and effort to teach them and REQUIRE standards.
 
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Old 06-03-05, 11:30 AM
T-Square
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Bravo!!
I respect anyone wanting to do a job right. I'm not a roofer by any means, but have also done reroofs over the years, and always took pride in doing it right. As I would if it was my own home. But I've also heard many guys swear by tear-off's before roofing, where in fact most roof structures can support up to four reroofs before taking it all off. If it's done right it will last leak free for another 25 years. And most homeowners are not aware of that fact. But then some roofers don't realize thats what the 2" roofing nails are for just that, four layers of roofing materials. Any roofer worth his salt, would inspect the attic, for wet or dry rot of rafters and sheathing. And how many roofs have we done where the roof sheathing was only 3/8" thick (homes of the 50's and 60's) and would not even stand the weight of two layers of roofing.

I have a reroof coming up on my own home, but I've got to add two rooms over the garage (attached) and the reroof will match the new roof. As long as my knees don't give out, and my thumb stays out of the way.

I'm still working on the drawings for this remodel, and may go with a metal standing seam roof, depending on the cost of materials for this whole remodel job, and the bath room fixtures I want.

And I have some questions about a built-up roof, over 1 1/2" T&G on beams.

How much air space above solid foam between 2x6 purlins on 24" centers is required for roof air flow?
 
  #9  
Old 06-03-05, 12:10 PM
63Sting
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I'm no roofer by anymeans, so take my post as such.
Adding a layer over existing shingles... you hsoudl be sure that the roof can support the additional load as well as snow if that is something that occurs in your region. I think 2 layers are ok, but not a third so I would rip the old and start anew. The house I am currently in the processof getting has 2 layers on it already, and that is what I plan to do.
 
 

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