Architectural Flashing Supply
Start a Quote
High wind and extreme weather systems · Lesson 2 of 4

High wind and extreme weather systems: materials, standards and design constraints

Which document answers which weather question: the ASCE 7 edition and map, the IBC edge rule and ES-1, tornado provisions, the Florida High-Velocity Hurricane Zone, hail test classes, how metal reacts to hail, and what a manufacturer rating or warranty means.

You will be able to: Match each hazard to the document that answers it, say what ASCE 7, the IBC, ES-1, the Florida protocols and the hail test classes cover, and state what each does not cover.

15 min · 12 slides · 12 questions

All lessons in this module
Slide 1 of 12

Which document answers which question

Each hazard has its own document. Wind design speed comes from the adopted ASCE 7 edition and map. A roof edge is tested to ES-1. Hail impact classes come from UL 2218 and ANSI FM 4473. Tornado loads come from ASCE 7-22 Chapter 32. The authority having jurisdiction names which edition applies.

Which document answers which questionFive panels on a navy field. Hurricane: Saffir-Simpson scale from the National Hurricane Center tells you the sustained wind class, not surge, flooding or design speed. Tornado: EF scale from the National Weather Service is a damage-based estimate, not a design wind speed; ASCE 7-22 Chapter 32 covers tornado loads. Design wind: the ASCE 7 edition and map give the design speed for a site; ask the local authority which edition applies. Roof edge: ES-1 tests RE-2 and RE-3 show tested assembly strength, not other assemblies or slopes over 2:12. Hail: UL 2218 or ANSI FM 4473 give an impact class for a covering, not wind performance of edge metal.Which document answers which questionHurricaneScale: Saffir-Simpson (NHC)Tells you: sustained wind classNot: surge, flooding or design speedTornadoScale: EF (NWS); ASCE 7-22 Ch. 32Tells you: damage-based estimateNot: a design wind speedDesign windDocument: ASCE 7 edition and mapTells you: design speed for a siteNot: the edition; ask the local authorityRoof edgeTest: ES-1 RE-2 and RE-3Tells you: tested assembly strengthNot: other assemblies or slopes over 2:12HailClass: UL 2218 or ANSI FM 4473Tells you: impact class of a coveringNot: wind performance of edge metal

Five panels on a navy field. Hurricane: the Saffir-Simpson scale gives a sustained wind class, not surge, flooding or design speed. Tornado: the EF scale is a damage-based estimate, not a design wind speed; ASCE 7-22 Chapter 32 covers tornado loads. Design wind: the ASCE 7 edition and map give a design speed for a site; ask the local authority which edition applies. Roof edge: ES-1 tests RE-2 and RE-3 show tested assembly strength, not other assemblies or slopes over 2:12. Hail: UL 2218 or ANSI FM 4473 give an impact class for a covering, not wind performance of edge metal.

A summary of lesson 2. Each document answers one question; none replaces the engineer of record or the authority having jurisdiction.

Sources

Glossary

ANSI/SPRI/FM 4435/ES-1
The test standard for edge systems used with low-slope roofs (9.5 degrees, or 2:12, or less); its tests RE-1, RE-2 and RE-3 cover copings and roof edge systems.
RE-3 test
The ES-1 coping test, which loads the top and the face of a full-size installed specimen in a ratio of 1.73 to 1 and counts loss of securement of a component as failure.
Risk category
The ASCE 7 and IBC classification of a building by the consequence of failure; IBC 2024 sends category III and IV buildings in the tornado-prone region to Chapter 32.
Tornado-prone region
The area of IBC 2024 Figure 1609.5 where risk category III and IV buildings follow ASCE 7 Chapter 32 tornado loads. A tornado-designed building is not a storm shelter without ICC 500 and the other shelter requirements.
High-Velocity Hurricane Zone
Florida's HVHZ, where the roofing rules use the RAS and TAS protocols; its local rules differ from the rest of the country.
UL 2218 impact class
A laboratory rating of a roof covering by dropping a steel ball: Class 4 is a 2 inch ball from 20 feet, at 23.71 ft-lbf. It is not a wind test.
Cosmetic hail damage
Dents and marks that do not change how the roof works; damage becomes functional when the coating is compromised, a seam is damaged, or water gets in.
Sustained pressure (Drexel)
The published test value Drexel gives for an ES-1 system, as printed for that system, its cover and size limits; the design engineer applies the factor of safety.