DerbyDad03 wrote:
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 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