What causes nail pops on roofs?
Short answer. Roof nail pops are mostly caused by the decking moving: plywood or OSB swells and shrinks with attic heat and humidity and slowly pushes nails up, especially nails that were too short, underdriven, angled, or that missed solid wood. Poor attic ventilation, decking installed wet, and nails driven into gaps between panels make them worse.
The main causes
- Wood movement: decking expands as it absorbs moisture and shrinks as it dries. Each cycle can lift a nail a little, and over years the nail backs out.
- Short nails: the building code calls for roofing nails to penetrate at least 3/4 inch into the decking or all the way through it. Nails that barely grip pull out easily.
- Underdriven or angled nails: a nail left sitting proud or driven at an angle never seats, and the shingle above presses on it until it wears through.
- Missed nails: nails driven into a gap between panels or at the edge of a knot have nothing to hold.
- Poor ventilation: a hot, humid Georgia attic swings decking moisture more widely, which speeds up movement.
- Wet lumber: decking installed wet shrinks as it dries and loosens its nails.
Why they matter
A popped nail lifts the shingle above it, breaks its seal, and eventually wears a hole through it. Water then runs down the nail shank into the decking. A few pops are routine maintenance; dozens point to a ventilation or decking problem that repairs alone will not solve.
Preventing them
- Correct nail length and placement in the manufacturer's nailing zone.
- Nail guns adjusted so heads sit flush, not proud or cutting into the shingle.
- Balanced soffit intake and ridge or roof exhaust ventilation.
- Decking kept dry before shingles go on.