Expansion joints and thermal movement · Lesson 2 of 4

Expansion joints and thermal movement: materials, standards and design constraints

Coefficients by metal, who decides joint type and spacing, the ED-1 rules, two federal specifications that give different spacings, and why sealant fills a joint but is not the joint.

You will be able to: Identify the expansion coefficients of the common flashing metals, who sets joint spacing and detail, and why published spacing rules disagree.

10 min · 11 slides · 7 questions

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Slide 1 of 11

Coefficients by metal

AFS's material register gives these coefficients:

Galvanized or Galvalume steel: 6.5 x 10^-6 per degF.
Aluminum: 12.9 x 10^-6 per degF.
Copper: 9.4 x 10^-6 per degF.
Stainless steel: 9.2 x 10^-6 per degF.
Mean values over about 68 to 212 degF where the source gives a range (steel gives none). Another table differs for copper and stainless steel, so name the source.

Sources

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

Glossary

Slotted hole: A clearance hole made longer than the fastener so the part can slide past it as the metal moves.
Loose-lock seam: An interlocked seam left free to slide, which UFGS and VA call for at expansion joints and fill with sealant.
Slip joint: A joint where one section slides over or into the next so the metal can move; VA calls for slip-type or loose-locked joints filled with sealant.
Project specification: The written requirements for a job. Published spacings such as those in UFGS and VA are examples; the project specification governs.