Vertical expansion joints accommodate thermal and structural movement in wall systems. This article outlines best practices for detailing, sealing, and flashing these joints across different cladding types including EIFS, masonry, and continuous insulation assemblies.
Purpose and Placement
Vertical expansion joints are used to allow for building movement due to thermal changes, shrinkage, seismic forces, or differential settlement. Placement is typically required every 20–30 feet in EIFS and masonry systems or at structural column lines in framed walls. Avoid aligning joints over sheathing panel seams unless properly backed.
Sealant and Backer Rod Selection
- Use closed cell backer rod to control joint depth and provide substrate for tooling
- Select sealants rated for 25–50% joint movement (ASTM C920 Class 25/50)
- Tool sealants to concave shape and ensure adhesion to both sides—not the back
Flashing and Drainage Considerations
Install through-wall flashing and weeps above and below expansion joints in masonry walls. For EIFS or rainscreen, integrate membrane flashing behind and below the vertical joint to drain incidental moisture. Ensure WRBs are lapped over expansion joint substrates and sealed with liquid or tape membranes.
Common Errors and Maintenance
- Underfilled joints or no backer rod—leading to premature cracking
- Sealants incompatible with EIFS or WRB surfaces
- Neglected joint inspection and replacement cycles (typically 7–10 years)
- Joints placed in corners or near fenestrations—high stress locations
Inspect joints annually for signs of movement, cracking, or detachment. Use field adhesion tests and cut-and-peel methods to confirm long-term sealant bond strength.
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