Roof-to-wall transitions are a common failure point for air leakage and water infiltration. This article explains how to detail these junctions for long-term durability, energy efficiency, and moisture control in sloped and low-slope roof systems.
Challenges at Roof-Wall Transitions
- Misaligned sheathing and structural framing creating air barrier gaps
- Improper or reversed flashing laps at step and head flashing locations
- Membrane incompatibility between vertical WRBs and horizontal roof underlayments
- Cracking and thermal movement at dissimilar material junctions
Control Layer Continuity
Ensure the air, vapor, and water barriers are lapped and sealed in a continuous, shingle-style sequence. Tie wall WRBs into self-adhered roof underlayment with flashing tape or fluid-applied membranes. Use step flashing on sloped roofs with kick-out diverters at eaves to direct water away from walls.
Installation Tips
- Terminate vertical WRB with a compatible transition membrane under roof cladding
- Use peel-and-stick ice and water shield under roof edge and behind siding
- Lap step flashing with siding and underlayment to prevent water traps
- On low-slope roofs, extend roof membrane up the wall at least 6–8 inches and counterflash
Quality Assurance and Inspections
- Inspect step flashing overlap direction and termination points
- Confirm membrane adhesion and sealant compatibility at changes in plane
- Photograph step-by-step roof-to-wall detailing prior to siding install
- Check for air barrier continuity with smoke pencil or blower door testing
Ensure all materials used meet local code for climate-specific wind and moisture performance.
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