Roofing: Do Nail Pops Require Tear Off?


I have a basic side gable roof, consisting of a single layer of ~20 year old standard three-tab asphalt shingles over 3/4" T&G sheathing.
There are a number of nail pops that have lifted some tabs and some that have actually punched through. There are a couple of spots where the sheathing has gotten wet which I have dealt with by banging the nails down and smearing roofing tar on the holes while I get some estimates.
One contractor told me that while he is surprised that I have nail pops in T&G sheathing, he is confident that he can pound the nails back down and add a layer of architectural shingles, avoiding a tear off.
My obvious concern is the possibility of *future* nail pops in other locations. Even if he pounds the existing pops down, what is going to prevent other nails from popping later? He also mentioned that nail pops are not as big an issue with architectural singles due to their thickness.
He is going to give me an estimate for both a tear off and a non-tear off installation and leave the choice to me.
Im interested in what others think about adding a second layer as opposed to a complete tear off.
Im also interested in what would occur if I opted for a complete tear off. Would *all* of the old nails be removed or would they just be pounded down anyway?
Thanks!
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My obvious concern is the possibility of *future* nail pops in other locations. Even if he pounds the existing pops down, what is going to prevent other nails from popping later? He also mentioned that nail pops are not as big an issue with architectural singles due to their thickness.
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That would be my concern also. I'd to a tear off.
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That implies that a tearoff includes the removal of *all* old nails, right?
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DerbyDad03 wrote:

If they're popping now, they'll continue. I, personally, wouldn't put new $$ on top of such a condition; others may disagree.
My experience has been most on a tear-off will not pull nails unless forced to do so and monitored _carefully_. Again, personally, I do pull but when doing work oneself, one can control what happens...
The biggest problem I would have would be it _might_ hold but if it doesn't, I think the warranty on the new will likely expressly exclude covering the problem as they'll attribute the failure to improper installation.
--
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I'm not surprised that you're having nail pops with 3/4" T&G, and I'd bet dollars to donuts that the roofer used his standard length roofing nails (used on 1/2" plywood/OSB sheathing) and the nails aren't protruding far enough through the sheathing. Some of the nail pops are probably from the nails hitting the T&G gaps and not having enough to bite into.
http://www.askthebuilder.com/487-Roofing-Nails-That-Pop-Up.shtml
The remaining nails are often just swatted into the sheathing after a tear-off. The new roofer is right that the heavier dimensional shingles are not as susceptible to nail pops and that the nail pops wouldn't telegraph through two layers. Dimensional shingles not being perfectly flat also make it tougher to see minor imperfections such as minor nail pops.
See if your new roofer would be willing to guarantee against the nail pops telegraphing through for a couple or three years. I'm thinking he won't, as it's your problem and you're making the choice, but you never now.
R
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As far as I can visually tell, the problem may be more related to the nails hitting the G in the T&G as opposed to the nails not being the right length.
When I look in the attic, I can see the nails protruding through the sheathing as per the site you offered. "The sharp tip of the roofing nail should completely pass through and extend approximately 3/8 inch past the underside of the roof sheathing."
Thanks for the info.
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