Metal roofs, walls and rainscreens · Lesson 2 of 4

Metal roofs, walls and rainscreens: materials, standards and design constraints

The IBC wind and test routes for metal roofs, code and maker minimum slopes, what each uplift, water, air and rainscreen test measures, why a rating belongs to its assembly, and material thickness minimums.

You will be able to: Name the code sections and test standards that govern metal roof and wall systems, apply code and maker minimum slopes, read a rating as belonging to one assembly, and compare material thickness with code minimums.

14 min · 12 slides · 12 questions

All lessons in this module

Slide 1 of 12

Code edition and wind pressure

The code text used here is the 2021 International Building Code as the City of Seattle adopted it; a project follows the edition and amendments its own building official adopts.

IBC 1504.4 requires mechanically attached roof coverings to resist the design wind load pressures for components and cladding.

Sources

2021 Seattle Building Code, Chapter 15 Roof Assemblies and Rooftop Structures (the 2021 International Building Code as adopted by Seattle): 1504.4, 1507.4 - City of Seattle, Seattle Department of Construction and Inspections

Videos for this lesson

What this video shows: A Sheffield Metals technical department explains what uplift tests share, UL 580, UL 1897, ASTM E1592 and how roof components factor in. One supplier's explanation; the listed assembly governs. Checked against the video's description.

Video: Metal Roof Uplift Testing Deep Dive: UL 90, UL 580, UL 1897, ASTM E1592 by The Metal Roofing Channel, on YouTube. Chosen from the video's published description.

What this video shows: A METALCON session on rainscreen wall designs, claddings and attachments, the air cavity and why its width matters, water control, structure, fire and exterior insulation. Checked against the video's description.

Video: What Makes Rainscreen Walls Work by METALCON, on YouTube. Chosen from the video's published description.

Glossary

Design pressure (TDI evaluation): The pressure a Texas Department of Insurance product evaluation lists for one tested assembly of panel, deck, clip and spacing. It is a listed value for that assembly, not a pressure your roof must resist.
UL 580 class: A UL 580 result of 15, 30, 60 or 90, nominal pressures in psf, where a higher class covers a lower one; it is not a wind speed.
UL 1897 result: The maximum load a roof covering attachment sustained in a UL 1897 test, reported in psf rather than as a class.
FM 4471 Class 1 panel roof: A panel roof approved under FM 4471 for fire, wind uplift, foot traffic and hail, with wind classes from 1-60 upward in steps of 15 psf.
Minimum slope: The lowest roof slope at which a system is allowed. The code sets a floor for each seam type, and a maker can set a steeper one; the stricter governs.
AAMA 509 and AAMA 508: Rainscreen test standards as MCA describes them: 509 classifies drained and back-ventilated systems with no pass or fail, and 508 sets pass or fail for pressure-equalized systems.