Expansion joints and thermal movement · Lesson 4 of 4

Expansion joints and thermal movement: defects, verification and case study

What restrained and cracked runs look like, the joint checks for gravel stops, copings and gutters, a field checklist, a joint-count example and a case study to document.

You will be able to: Recognise the defects that movement causes, check a finished run against a field checklist, work a joint count with stated inputs, and document a defect and a corrective request.

10 min · 12 slides · 7 questions

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Slide 1 of 12

What a restrained run looks like

UFGS 07 60 00 requires finished sheet metal assemblies to be weathertight without waves, warps, buckles, fastening stresses or distortion, while allowing for expansion and contraction without damage.

AFS's Failure Atlas lists too little allowance for thermal expansion as a cause of oil-canning: a panel restrained against movement bows.

Sources

UFGS 07 60 00 Flashing and Sheet Metal (August 2023, Change 1 05/25) - USACE / NAVFAC / AFCEC, published by the Whole Building Design Guide
AFS Division 07 technical notes - Architectural Flashing Supply

Glossary

Oil-canning: Visible waviness of a flat metal face; AFS's Failure Atlas lists restraint against thermal movement as one cause.
Fatigue cracking: Cracking from repeated temperature cycling concentrated at one seam, fastener or bend where the detail gave no expansion relief.
Ponding: Water that stays on a roof or in a gutter; failed expansion joints or seams that form a dam are one cause listed in AFS's Failure Atlas.
Expansion relief: A detail, such as a joint, that takes movement so it is not concentrated at one seam, fastener or bend.