Should roofing nails go through the plywood?
Short answer. Yes, on most roofs they should. The code requires shingle nails to penetrate at least 3/4 inch into the deck or go completely through it when the deck is thinner than 3/4 inch, and since most Georgia roofs use 7/16 inch OSB or 1/2 inch plywood, rows of nail tips showing in the attic are a sign of correct installation.
Why through is the goal
A nail's holding power comes from the wood it grips. On a thin deck, the only way to get full grip is to use the whole thickness, so the point exits the underside. Shingle wind ratings are tested that way, and the International Residential Code writes the rule in directly.
What a good pattern looks like from the attic
- Neat horizontal rows of points, spaced to match each course of shingles.
- Points roughly the same length, showing consistent nail depth.
- No large areas without points, which could mean nails missed the deck or were placed too high.
Things worth a closer look
- Rusty points: moist attic air condensing on cold nails, a ventilation issue.
- Dripping or frost on points in winter: the same problem, more common in mountain homes.
- Points with gaps around them or daylight: possible missed nails or damaged decking.
- Old board decks: nails that land in the gaps between boards hold nothing.
When they should not show
Where decking is 3/4 inch or thicker, or where the underside is a finished ceiling such as a porch or an open eave with tongue and groove boards, nails are sized to reach the required depth without poking through. Points visible on a finished porch ceiling mean the nails were too long for that area.
Wear a hard hat or cap in the attic; those points are sharp. See roof ventilation basics and OSB vs plywood roof decking.