Roof Nail Pops Revisted - Do They Really Happen?


I just got a call from a roofer who looked at my roof and prepared an estimate. Some of you may recall that I had what I called nail pops pushing through the tabs of my 20 YO asphalt shingles.
All of the following statements are "according to him"
- There is no such thing as a "nail pop". - Ring shank roofing nails cannot back themselves out due to contraction-expansion cycles or any other reason. - In my entire career, I have never seen a roofing nail back itself out and I have done hundreds of roofs for all of the high-end builders in the area. They wouldn't use me if I didnt know my stuff. - The reason your house has nail heads popping through the shingles is because these were "high nails" - nails that were never properly set by the contractor who installed the roof. The compressor didn't seat the nails completely and the roofer was too lazy to grab a hammer and pound them down. - I will hammer all of your high nails down and add a second layer over the original - I will guarantee, in writing, that the original nails will not back themselves out and damage the new roof.
So what's the deal? Can roofing nails back themselves out as I have heard from many sources or does this guy know the "real story"?
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DerbyDad03 wrote:

They can (and do) and many roofing nails aren't ring-shank, anyway.
I can show you pictures of siding nails (ring shank as well as straight) that over the years have worked themselves 1-2 _inches_ out of 80+ yr old first growth yellow pine studs (that can't drive a nail into easily at all owing to how hard they are)...
He's blowing smoke on most of the points. The only point on which I would give him full credit is that it is possible there were high nails left originally...
--
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On Mon, 18 Aug 2008 09:25:59 -0700 (PDT), DerbyDad03

I've never heard of roofing nails backing out either. Unless somebody was inside bounding the ends upward, I can't think of a backing out mechanism, especially if the shingles are flat.
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DerbyDad03 wrote:

They can and do back themselves out and become "nail pops". My engineer explained the process like this; The wood will swell if there is enough moisture in the air and will sometimes swell around a nail. When the wood dries out, the nail is looser in the hole. The sun heats the shingles which expand both laterally and in thickness. This causes the shingle to "grab" the nail and the vertical expansion lifts it slightly. Repeat this process numerous times and the nail can be lifted enough to cause a problem.
Your roofer is the only roofer that I know that has never heard of nail pops. I would suspect his other abilities.
-- Robert Allison Rimshot, Inc. Georgetown
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Robert Allison wrote: ...

I don't think the shingle has much to do with the process, actually--they're too soft.
The heat/cooling expansion/contraction cycle combined w/ some moisture, particularly add in perhaps a void in plywood sheathing for roofing nail in particular and most of all time and eventually a few will work their way back out.
In very windy areas, such as here on the High Plains, the physical vibration/working of the material can cause it at a much higher rate than in other areas. As noted, it's very common here on siding or even construction joints w/ age as well as roofing to see many nails projecting by as much as an inch or more. In the 30+ years in VA and TN where weather isn't nearly as severe (particularly wind) I never experienced nearly the amount as is common here.
--
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Bzzzt. I'm sorry, that's a wrong answer.

Bzzzt. Did you offer up the term ring shank roofing nail or did he? The common roofing nail term was a barbed roofing nail - there were little raised ridges just under the head that were on opposite sides of the shank. Ring shank nails have rings running pretty much the entire length of the shaft. Nowadays the barbed nails are referred to as smooth because there are ring shank roofing nails. Considering that your roof is 20 years old it was probably pneumatically fastened with smooth/barbed nails and not ring shanks. You can determine this for yourself by checking out the protruding part of the nail from your attic. If you do have ring shanks I'd be surprised. Roofers don't usually use them unless they're asked to do so.

His warranty lasts a year. Your roof will be expected to last until the guy is well retired, right?

That is possible. If you do indeed have ring shank nails it is more likely that they weren't set correctly in the first place. It does not mean that you can't ever never ever have nail pops.

He's talking the talk. Like I said before, I don't think you have too much of a worry with reroofing with the heavier dimensional shingles. They are far less likely to suffer from nail pops.
You should have asked him how the ring shanks hold when the nail hits a gap between sheathing boards.

Check his hands and feet for stigmata. If he has some, then he's probably right. Otherwise he has an opinion that is contradicted by virtually everyone else.
R
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BTW, it seems to me that you might be over-analyzing this. There are plenty of good contractors who don't see eye to eye on specifics. You will not find a perfect consensus on anything in construction.
R
Very good point and very well said that applies to almost all contracting situations.
Colbyt
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Strike 1

Strike 2 - Ring Shank roofing nail???

Strike 3. The rest is moot.

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