Wind Damage
What the exam tests
Wind Damage tests how wind loads roofs, how damage appears, and how to establish causation and extent. Expect questions on uplift and suction, edge and corner effects, seal-strip and fastener failures, debris impact, storm direction, and documentation that separates wind damage from installation defects and aging.
Core rules and concepts
- Wind loading: roof uplift is largely suction. In ASCE 7-style terms, velocity pressure is q = 0.00256 V² psf at standard air density, then adjusted for exposure, height, topography, and internal pressure. Openings and breached walls increase internal pressure and uplift.
- Concentration zones: ridges, hips, gables, eaves, corners, and perimeter edge metal see higher demand. Damage that follows these zones is more consistent with wind than scattered damage in the field.
- Failure mechanisms: seal-strip release, shingle creasing or mat tearing, fastener pull-out, membrane billowing and peel, edge-metal deformation, and wind-borne debris impact.
- Causation: compare the observed damage with the assembly rating, reported wind speed and direction, building exposure, age, maintenance, and installation quality. A single missing shingle is not enough.
- Documentation: record elevation and slope orientation, use scale photographs, lay out test squares, note collateral debris and nearby undamaged roofs, and obtain weather data.
Worked example
A two-story gable roof has 3-tab shingles rated ASTM D7158 Class D (90 mph). A storm from the southwest produced a reported 78 mph gust. Shingles are missing on the north slope near the ridge and gable end; remaining seal strips near the damage are broken; several tabs show creases; ridge caps are missing; and matching shingle debris is in the yard. Reasoning: the damage is concentrated at the ridge and gable edge, where suction is highest; seal-strip release and creases indicate uplift rather than foot traffic; and debris confirms recent displacement. Although the reported gust is below the class rating, local roof-height exposure and gust effects can exceed the report. The pattern supports wind damage, but nail placement and shingle age should still be checked.
Traps that cost marks
Do not attribute all missing shingles to wind, rely on one test square, or ignore storm direction. Do not treat an anemometer report as the roof-level wind speed. Distinguish straight-line wind patterns from tornado or debris damage, and check interior openings that could raise pressure.
Key points
- Wind uplift is mainly suction; q = 0.00256 V² psf at standard density, adjusted for exposure and height.
- Damage concentrates at edges, corners, ridges, gables, and openings; internal pressurization raises uplift.
- Confirm wind with seal-strip release, fastener pull-out, membrane peel, edge-metal deformation, and debris.
- Compare damage with assembly rating, wind speed and direction, age, maintenance, and installation quality.
- Document compass orientation, scale photos, test squares, and weather data; never rely on one shingle.