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High wind and extreme weather systems · Lesson 4 of 4

High wind and extreme weather systems: defects, verification and case study

How roof edges fail in storms, what the field record from Andrew, Ivan and Michael shows, how to inspect after a storm, cosmetic and functional hail damage on metal, how to verify a claim, FEMA corrective options, a fictional case study and the evidence to document.

You will be able to: Read a wind or hail failure pattern, decide whether damage is cosmetic or functional, check a product claim against a test, and write the evidence a reviewer needs.

13 min · 11 slides · 10 questions

All lessons in this module
Slide 1 of 11

How roof edges fail

FEMA says low-slope membrane roofs on public buildings often fail at the edges in high winds, from lifting and peeling of edge flashings, copings or fascia covers.

SPRI says edge metal must stay attached in high winds even if it does not secure the roof.

FEMA says a gutter lifted by wind causes the edge flashing that laps it to lift as well, resulting in a progressive peeling of the roof membrane.

A coping and its load pathSection through a parapet wall with a coping. A red cover sits over a charcoal cleat caught in its hems, on a wood nailer anchored into the wall. Concealed screws pass through the cleat into the nailer. A navy arrow shows wind suction lifting the cover upward, and another shows it pulling outward on the outside face. Six numbers mark the load path: cover, cleat, fastener, nailer, anchor and wall.upliftoutward132456Wind load path, not to scaleroofoutside

Section through a parapet wall with a coping. A red cover sits over a charcoal cleat caught in its hems, on a wood nailer anchored into the wall. Concealed screws pass through the cleat into the nailer. A navy arrow shows wind suction lifting the cover and another shows it pulling outward on the outside face. Six numbers mark the load path: cover, cleat, fastener, nailer, anchor and wall.

1
Cover (AFS-fabricated coping)
2
Cleat, caught in the cover's hemmed drip
3
Fastener through the cleat into the nailer
4
Wood nailer on top of the wall
5
Anchor from the nailer into the wall
6
Parapet wall, the structure that takes the load
Not to scale; a simple snap-on coping drawn to show the chain of parts, not a tested assembly. If any link fails, the cover can lift or peel. The cleat, spacing and fasteners of a real job come from the specification and the tested system.

Sources

Videos for this lesson

What this video shows: A 59-second clip from a testing laboratory titled as an ES-1 RE-3 coping test; its description quotes SPRI's opinion that ES-1 testing should be performed on systems as manufactured by a given fabricator.

Video: ANSI/SPRI ES-1 Coping Pull Off - RE-3 Test by National ES Testing Service Tunney, on YouTube. Chosen from the video's published description.

Glossary

Edge peeling
Lifting and peeling of metal edge flashings, copings or fascia covers in high wind, which can then peel back the roof membrane behind them.
Peel-stop bar
A well-anchored bar over the membrane near the edge flashing or coping, recommended by FEMA where cleats attach the membrane, as secondary protection against lifting and peeling.
Functional hail damage
Damage that affects performance on metal: a compromised factory coating, or a seam dent that damages the embedded sealant and can let water in.
Seam water test
A check in which a container is filled to about twice the height of the seam to see whether water gets past the sealant.
Same manner as tested
The ES-1 requirement that to perform as tested, a roof edge system is installed in the same manner as the tested system, with the same cleats, fasteners and spacing.
Photo log
A dated set of photographs with location, scale and notes that lets a reviewer follow what was seen without being on the roof.
Load path
The continuous chain that carries wind load from the cover through the cleat and fasteners to the structure; a weak link breaks the path.