Flashing geometry and movement accommodation · Lesson 2 of 4

Flashing geometry and movement accommodation: materials, standards and design constraints

How coefficients differ by metal and by source, why zinc needs a roll direction, how published design ranges and specifications differ, and what ED-1 says about thickness and cleats.

You will be able to: Compare published coefficients by metal, choose and record a design temperature range from published examples, and name the standards and specifications that set joint and thickness rules for roof edge metal.

10 min · 11 slides · 7 questions

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Slide 1 of 11

Coefficients differ by metal

Over a 10 ft length and a 100 degF change, AFS's material register gives galvanized steel 0.078 in, copper 0.113 in, stainless steel 0.110 in and aluminum 0.155 in.

Name the source of the coefficient in your calculation, because sources print slightly different values.

Sources

AFS material register (alloys, thicknesses, weights and expansion coefficients) - Architectural Flashing Supply

Glossary

Coefficient of expansion: The length change per unit length per degree for a metal. AFS's register gives it per metal, and published sources differ slightly.
Rolling direction: The direction the zinc sheet was rolled in; RHEINZINK and VMZINC print different expansion along it and across it.
Metal surface temperature: The temperature of the metal itself, which AFS's thermal method uses instead of the air temperature.
Exposed face: The visible face of a roof edge component; ED-1 sets the minimum metal thickness for flatness by the width of this face.
Cleat: The strip a roof edge component engages on; ED-1's commentary distinguishes continuous cleats from intermittent clips, and ED-1 generally recommends a cleat be one gauge heavier than the material it holds.
Oil canning: Waviness of a flat metal face; ED-1 says increased thickness reduces the oil-can effect, and PAC-CLAD says it does not affect finish or structural integrity.