What Are Nail Pops on a Roof, and Are They a Problem?

The basics

What is a nail pop on a roof?

It's a roofing nail that has worked its way back up out of the wood deck. Each nail sits under the next row of shingles, so a raised one pushes up on the shingle covering it.

Every asphalt shingle is held by nails driven through a band near its top and into the plywood deck. The next row laps over those nails, and a strip of adhesive seals each row down to the one below. The nail heads should sit flush, never cut into the shingle, and never show on the finished roof. InterNACHI, the home inspectors' association, describes nail pops as the spots where fasteners have backed out. You usually notice them as:

• A small bump or raised spot under a shingle
• A shingle edge that won't lie flat against the one below
• A nail head showing through a shingle, sometimes rusty
• A small hole worn in a shingle

They're small, so from the yard you may only see a shingle that looks a little lifted.

Leaks

Do nail pops cause leaks?

They can, over time. A raised nail keeps the shingle over it from sealing and can wear a hole through it, and a nail that ends up exposed can rust and let water in around it.

• The shingle above can't seal. GAF says raised nails interfere with the sealing of the shingles.
• The head wears through. InterNACHI says a protruding nail head will eventually wear a hole through the shingle lying over it.
• The exposed nail rusts and the hole grows. GAF's technical bulletin says exposed nails can corrode and let water in, and the nail's hole may get bigger. InterNACHI adds that expansion and contraction can widen nail holes enough to leak.

A pop caught early is a small fix. One that's ignored can let water reach the plywood, and a slow leak nobody sees is how decking rots. See damage to the roof deck under your shingles for what that looks like.

Installation

When do lots of nail pops mean the roof was installed wrong?

When pops show up across a roof that's only a few years old, look at the nailing first. No one publishes a number of pops that proves a bad install, but InterNACHI ties nail pops to nailing that wasn't done to the manufacturer's specifications.

Florida's building code sets the floor, and the shingle maker's instructions set the rest.

Nailing mistakes also fall outside shingle warranties. GAF's warranty excludes damage caused by improper fastening, and the re-roofing section of Atlas's Pinnacle Pristine instructions says incorrectly placed nails will void the wind coverage. We're a roofing contractor, not a lawyer, so read your own warranty for its exact terms.

So a newer roof covered in pops is a workmanship question first. Call the company that installed it and pull out their workmanship warranty. (Ours runs 5 years on every replacement.) If it's also leaking, read why a new roof leaks. Shingles curling or dishing across a whole slope, rather than bumping up over single nails, are a different problem: see what curling and cupping shingles mean.