A nail pop, in roofing terms, occurs when a roofing nail gradually backs out of the roof deck, pushing up through the shingle above it and creating a small raised bump or, if it works far enough out, an exposed nail head vulnerable to water intrusion around its shaft.
This can happen due to improper original installation, like a nail driven at an angle or into a knot in the wood decking, seasonal expansion and contraction of the roof deck, or general settling over time.
Once a nail head is exposed or a popped nail creates a raised bump beneath a shingle, that specific spot becomes vulnerable to water working its way in around the nail shaft or through the disrupted shingle surface above it.
What Causes a Nail Pop?
- Improper original nail placement or angle
- Seasonal expansion and contraction of the roof deck
- Nails driven into a knot or defect in the decking
- General settling or movement over time
Why Are Nail Pops Important?
An exposed or partially backed-out nail creates a direct, if small, pathway for water to enter around the nail shaft, and the raised bump it creates beneath a shingle can also crack the shingle material above it over time, compounding the potential for water intrusion at that specific spot. This combination of direct water pathway and secondary shingle damage makes nail pops worth addressing promptly rather than ignoring as a minor cosmetic issue.
Repairing a nail pop typically involves removing or resetting the problem nail, sealing the hole it leaves, and repairing or replacing any shingle damage the popped nail caused, a relatively minor and affordable fix compared to the water damage an ignored nail pop could eventually cause.
Nail Pop vs. Roof Leak
A nail pop is a specific, localized cause of potential water entry at one particular fastener location. Roof leak is the broader outcome, water actually entering the structure, which a nail pop is one of many possible specific causes contributing to.