High Nails and Overdriven Nails: Installation Issues in Claims

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Two installation issues come up repeatedly in roofing evaluations: nails driven high, above the shingle’s printed nailing zone, and nails driven too deep, cutting into or through the shingle mat rather than sitting flush against its surface. Both are functions of how the shingle was fastened during installation, whether by hand or with a pneumatic nailer, and both leave a physical signature that can be documented well after the fact. A properly driven nail sits flush with the shingle surface, its head neither raised above the surrounding material nor sunk into it, and that flush condition is the reference point against which both high nailing and overdriving are measured during an inspection.

A high nail sits above the reinforced nailing strip and, because the course above overlaps that area, the raised nail head can create a small bump under the shingle it is covering, sometimes visible as a slight ridge or discoloration on the surface above. Over time, that raised point becomes a stress concentration where the overlying shingle can crack or wear prematurely, and in a wind event, a high nail provides less pull-through resistance because it engages a single layer of material rather than the two layers the nailing zone is designed to secure.

An overdriven nail is the opposite problem: the nailer’s pressure or air setting drives the fastener head down into or through the shingle’s fiberglass mat, breaking the seal the nail head would otherwise provide and creating a small opening where water can enter around the shaft. Overdriven nails are frequently found in clusters when a nail gun’s depth setting was not adjusted correctly for a particular shingle thickness or roof deck hardness, and they can appear across an entire roof or on isolated sections depending on when in the job the setting changed. A soft or spongy deck can compound the problem, since a fastener that would sit flush against a firm plywood surface can sink further into a deteriorated panel underneath, even with a properly calibrated nail gun setting.

In a storm damage evaluation, both conditions are documented as observed installation characteristics rather than storm damage, since neither is caused by wind or hail. Their presence can complicate an evaluation of overall roof condition, particularly when assessing how a roof performed during a wind event, because a roof with widespread high or overdriven nailing may show more shingle displacement than an equivalent roof that was fastened correctly, independent of the storm’s actual severity. Sorting out what that means for a particular claim is a matter for the parties and their experts, working from the documented facts.

Both conditions can originate from equipment settings as much as from an installer’s technique, since a compressor set too high for a given shingle thickness will overdrive fasteners consistently across an entire section until the setting is adjusted, while a worker fatigued late in a long day may drift high on a run of courses without realizing it. Photographing individual examples with a ruler or coin for scale, alongside wider photographs showing where on the roof plane the condition occurs, helps create a record that a later reviewer can evaluate without needing to have been present at the original inspection.

This article is provided as general education on the appraisal process. It is not legal advice, and procedures vary by state and by policy.

Based in Minnesota and serving clients nationwide, Russ Lis is a working property insurance appraiser and umpire. Contact Appraisal Resolution.