InterNACHI Wind Mitigation common mistakes
InterNACHI Wind Mitigation · Understand the traps and how to avoid them.
Assigning the roof-deck-attachment credit based on the nail size or spacing the inspector can see at the attic access hatch, then reporting that single pattern for the whole roof.
The attic hatch opening is the easiest and safest place to look, so candidates stop there. But attachment patterns routinely change across a roof after repairs, additions, or partial re-decks, and the weakest pattern governs the rating. Candidates also conflate 8d nails with 6d or staples because they only measure one or two fasteners.
What to do instead
Sample at multiple locations across the attic, including near gable ends, valleys, and any area that looks patched or newer. Measure the actual fastener length and shank diameter, record the spacing for each distinct area, and report the worst-case pattern found. Photograph each distinct pattern separately with the measuring device visible in frame.
Marking roof-to-wall attachment as a strap or clip when the connector is present but not actually installed to the manufacturer's specification, for example a strap nailed on only one side, or a strap that does not wrap over the truss.
Candidates see metal and assume credit. The distinction between a toe-nail, a clip, a single-wrap strap, and a double-wrap strap depends on nail count, strap length, and whether the strap goes over the top of the truss or is nailed to the side only. Inspectors also miss that the strap must be embedded in or attached to the wall below, not just the truss.
What to do instead
For every distinct connector type, count the nails, measure the strap gauge and length, check whether it wraps over the truss, and confirm attachment to the wall structure. Photograph the connector with a tape or ruler in the same frame, and note the truss spacing. When the installation is ambiguous, report the lower category rather than guessing.
Classifying roof geometry as hip roof based only on the fact that hips are visible, without calculating the proportion of non-hip features such as gable ends, dormers, and flat or shed sections.
The hip roof credit depends on a ratio of non-hip perimeter to total perimeter, and candidates eyeball it. Dormers, small gable vents, and porch extensions are easy to overlook from the ground, and candidates who do not walk the full perimeter miss significant gable sections at the rear.
What to do instead
Sketch the roof plan and label every perimeter segment as hip or non-hip, then compute the ratio rather than estimating. Include dormers, gable-end walls, and any flat or shed roof section in the non-hip total. Document the sketch or measurements in the report so the classification is reproducible.
Awarding secondary water resistance credit when the underlayment is a standard felt or a self-adhered membrane that does not meet the sealed-roof-deck definition, or when the SWR is present but not continuous over the entire roof.
Candidates see a peel-and-stick product and assume it qualifies. The credit requires a specific configuration, typically a self-adhered membrane applied directly to the deck and covering the full roof area, sometimes with a defined overlap and no exposed deck between courses. Partial installations around valleys or eaves are common and are not full credit.
What to do instead
Confirm the product type from labeling or the homeowner's documentation when possible, verify coverage extends across the entire roof deck rather than just valleys and penetrations, and photograph the membrane at multiple locations. If coverage or product type cannot be verified, report no credit and note the limitation.
Recording opening protection as fully compliant based on the presence of impact-rated glass in some windows, without confirming every opening is protected, including doors, garage doors, skylights, and glass block.
Garage doors and entry doors are the most commonly missed openings, and candidates often accept a homeowner's statement that all windows were replaced. Mixed protection, where some windows are rated and others have shutters or nothing, is very common in older homes.
What to do instead
Walk the exterior and count every opening, then verify protection for each one individually: impact-rated glazing with a visible label or etching, or an approved shutter or panel system with labeled hardware. Note the protection type per opening and photograph representative labels plus any unprotected opening. Report the weakest opening in the summary.
Submitting a report with photographs that lack scale, context, or identification, such as a close-up of a nail with no tape measure, or a strap photo where the truss and wall connection cannot be seen.
Candidates take photos quickly in a hot attic and assume the reviewer will understand what is shown. Without a scale reference or a wider context shot, a fastener photo cannot support a nail-size determination and a strap photo cannot show nail count or wrap configuration.
What to do instead
For each credit claimed, take a paired photo: a wider shot showing the location and context, and a close shot with a ruler or tape measure in the same frame. Confirm the photo is in focus and the key feature is legible before leaving the attic. Label photos by location in the report.
Treating the wind mitigation inspection as a general home inspection and reporting unrelated defects, code violations, or maintenance items in the mitigation form.
Candidates come from a home inspection background and default to defect reporting. The mitigation form is a data-collection instrument for insurance rating, and extraneous commentary can confuse or delay underwriting and may create liability outside the scope of the engagement.
What to do instead
Keep the report confined to the mitigation features and the documentation required for each credit. Note limitations and inaccessible areas, but do not editorialize on condition or recommend repairs. If a safety hazard is observed, report it separately from the mitigation findings.
Failing to document or verify the permit and construction date, or accepting the homeowner's stated year without evidence, when the age of the home drives which credits are even plausible.
Candidates rely on conversation rather than documentation. The year built affects expected construction methods, and a stated date can conflict with observed features, such as a strap system in a home claimed to be older, which should prompt verification rather than silent acceptance.
What to do instead
Record the year built from a verifiable source such as the property appraiser record or permit documentation, and note the source. When observed features conflict with the stated age, investigate and document the discrepancy rather than resolving it silently.
Overlooking the gable-end wall bracing and the continuity of the wall-to-deck load path when assessing envelope vulnerability, focusing only on the roof covering.
Gable end walls are a well-known failure point in high winds, but candidates concentrate on shingles and attachments because those carry explicit form credits. Missing the gable wall framing, sheathing, and bracing leaves the envelope assessment incomplete and misrepresents the structure's actual vulnerability.
What to do instead
Inspect and describe gable-end wall construction, including sheathing, framing, and any bracing or reinforcement, and note how the gable wall connects to the roof and ceiling structure. Include photographs. Treat the gable end as a required observation even when no credit depends on it.
Guessing or leaving blank the fields for features that could not be observed, rather than reporting them as not verified with a stated reason, and then filling the summary with an assumed best-case rating.
Candidates feel pressure to deliver a favorable result for the client and treat an inaccessible attic or a sealed skylight as an inconvenience to work around. Assumed values propagate into the final rating and mislead the insurer.
What to do instead
Use the form's not-verified or unknown option for any feature that could not be directly observed, and state the specific reason, such as no attic access or obstructed view. Summarize the rating using only verified features, and list the unverified items so the insurer can decide whether further inspection is warranted.