Chimney flashing is the combination of several distinct flashing types, typically including base flashing, counterflashing, apron flashing, and often a cricket, all working together to create a watertight seal around a chimney’s penetration through the roof surface.
Because a chimney presents a rigid, unmoving masonry structure penetrating a roof surface that can expand, contract, and settle slightly over time, this junction requires a more sophisticated flashing system than a simpler penetration like a plumbing vent pipe.
Given how many individual components and connections comprise a complete chimney flashing system, this location represents one of the more complex and skill-dependent flashing installations found on a typical residential roof.
What Does Chimney Flashing Include?
- Base flashing along the chimney’s downslope and side edges
- Counterflashing embedded into the masonry above the base flashing
- Apron flashing at the downslope side
- Often a cricket at the chimney’s upslope side to divert water
Why Is Chimney Flashing Important?
Given the complexity and number of individual components involved, chimney flashing systems are statistically one of the most common sources of roof leaks, particularly as sealant and mortar joints deteriorate with age or if the original installation didn’t follow proper multi-part flashing practices. This complexity is exactly why chimney flashing deserves particular attention during any roof inspection, whether for routine maintenance or before purchasing a home.
A cricket, a small peaked structure built on the chimney’s upslope side, becomes particularly important on wider chimneys, since without it, snow and water can accumulate against the chimney’s upslope face rather than being effectively diverted around it. This thorough evaluation is well worth the effort given how much can go wrong at this complex junction.
Chimney Flashing vs. Counterflashing
Chimney flashing is the complete, multi-part system protecting the entire chimney penetration. Counterflashing is one specific component within that system, covering the top edge of the base flashing where it’s embedded into the chimney masonry.