Steel penetrations such as beams, columns, and connectors often interrupt the air barrier plane in exterior walls. This article explains detailing strategies to seal around these transitions and maintain envelope performance.
Challenges at Structural Steel Interfaces
Steel penetrations through the air barrier can result in significant leakage paths and are prone to movement due to thermal expansion and structural loads. Without proper detailing, these can compromise building energy performance and lead to condensation within the wall cavity.
Sealing Techniques
- Use liquid-applied or peel-and-stick membranes rated for complex geometries
- Backwrap membranes around structural steel where possible to create monolithic seals
- Reinforce with mesh or transition tapes at irregular steel interfaces
- Tool compatible sealants around steel base plates, flanges, or outriggers
Thermal Considerations
Structural steel is highly conductive and can act as a thermal bridge. Apply rigid insulation or mineral wool tightly around steel penetrations and extend the thermal layer past anchors or supports. Use non-combustible insulation when steel supports fire-rated walls or floors.
QA/QC and Field Testing
Inspect all transitions visually and with adhesion tests. Perform blower door and infrared scanning at column and beam areas to confirm air sealing. Ensure sealants are applied to clean, primed substrates and reinforced where movement is expected. Confirm product compatibility with WRB and insulation materials.
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