Why Do Nail Heads Pop-Up Through Roof Shingles?

I’ve seen several inspectors reporting nails popping on asphalt roof system throughout the years. Take a look at the pictures above. You can see just below one shingle a nail that is working it’s way back out. Why does this happen? There are several different reasons why and the exact cause cannot always be determined:

Wrong Nail Depth: Under-driven or over-driven nails cause problems here. Nails that are not deep enough cause the nail to work its way to the surface over time. Over-driven nails may cause damage to the shingle and lift.

Thermal Expansion and Contraction: Roofing covering materials such as shingles experience thermal expansion and contraction. If this process is repeated over a number times, like over months or years of time, this can cause the nail heads to raise to the surface.

Incorrect Fastener Size or Using the Wrong Nails: Roof nails are specifically designed to hold shingles in place. They frequently have little groves cut into them, called ring-shank, that allow them to better grip the wood and remain in place. Using the wrong nails makes it easier for the nails to slip out. Using the wrong size nails does the same thing.

Shingle Quality Issues and Poor Installation: Cheap, junk shingles may shrink or warp and deteriorate prematurely. Shingles that are installed incorrectly may expose the nails to weather conditions they are not rated for. Expansion and contraction exacerbated by weather conditions like ice and extreme heat or cold accelerates this process. Shingles installed incorrectly can put excessive strain on the nails, causing them to move.

Structural Movement of the Roof: The entire structure moves over time as the house settles in place, and the roof moves as well. This can cause otherwise correct installations to experience nail-pops.

Water Penetration: When exposed to moisture due to leaks, inadequate ventilation, the nails can rust. When nails rust, they shrink, but the wood shrinks less, loosening the nail.

How Would I Fix It?

Often times this just isn’t a big deal and I wouldn’t worry about. Unless the shingle is in danger of being ripped off due to high winds OR you suspect water penetration due to this condition, I would probably leave it alone. If you want to fix it, consider hiring a professional to go on the roof to re-nail the shingle, replace the shingle if need, and caulk or seal any exposed nail heads.