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 didn’t 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"?
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
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.
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.
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.
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.
Very good point and very well said that applies to almost all contracting
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