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Essential Guide to Chimney Flashing Repair and Installation

Barry Martin
February 8, 2024

Chimney flashing plays a crucial role in maintaining your roof and chimney's integrity, acting as a barrier against water infiltration.

This comprehensive guide explores the importance of chimney flashing, its types, the repair and installation process, and bonus maintenance tips to ensure lasting protection for your home.

Understanding Chimney Flashing

chimney on the house roof

Chimney flashing is a material installed around the base of your chimney, creating a waterproof seal between the chimney and the roof​​​​.

It's typically made from materials like aluminum, steel, or copper, each with its advantages and suitability based on the chimney and roof type​​.

The Importance of Well-Maintained Chimney Flashing

  • Waterproofing: It prevents water from entering your home, safeguarding against leaks that can damage your roof, attic, and interior walls.
  • Prevents Rot and Mold: Keeping water out inhibits wood rot and mold growth, which is crucial for maintaining your home’s structural integrity.
  • Energy Efficiency: Properly installed flashing helps maintain energy efficiency by preventing heat loss.
  • Aesthetic Appeal: Well-maintained flashing contributes to the overall aesthetics of your home, keeping the roofline polished​​.

Identifying Signs of Faulty Chimney Flashing

chimney flashing repair sign

It's important to recognize when your chimney flashing may need repair. Common signs include:

  • Leaking Chimney: Indicates water seeping past the seal.
  • Water Stains: Signs of water damage on ceilings or walls near the chimney.
  • Rust Stains: Suggests that the flashing isn't deflecting water effectively.
  • Discolored Bricks: Can indicate a water-damaged chimney​​.

DIY vs. Professional Repair

While it is possible for homeowners to undertake chimney flashing repair as a DIY project, it requires specific skills and confidence in construction abilities. If unsure, it's advisable to seek professional help​​.

Cost of Chimney Flashing Repair

The cost of repairing chimney flashing varies. Professional repairs generally range between $700-$1500, while DIY repairs can cost around $100-$200, depending on the materials chosen​​.

This cost varies for different types of chimney flashing. For example, you must know and understand all the options you must choose from.

Here are the options you can choose from:

  1. Aluminum Flashing: Common and inexpensive, suitable for various roof types but prone to corrosion in certain conditions.
  2. Vinyl and PVC Flashing: Lightweight and slightly more expensive than aluminum, not ideal for chimneys due to brittleness and poor heat resistance.
  3. Steel and Galvanized Steel Flashing: Durable and corrosion-resistant, ideal for chimneys but more expensive and heavier.
  4. Copper Flashing: Resistant to extreme weather and high temperatures but more costly and challenging to install​​.

Tools Required for Chimney Flashing Repair

tools gif
  • Tools: Diamond blade, extension ladder, grinder, roof brackets, roof harness, tin snips.
  • Materials: Any of the chimney flashing from the four options, e.g., Galvanized sheet steel, anchors, coil stock, caulk, roofing membrane

Step-by-Step Guide to Repairing Chimney Flashing

  • Prepare and Remove Old Flashing: Set up safety equipment and remove existing flashing​​.
  • Find Roof Slope: Accurately measure the slope for precise fitting​​.
  • Cut and Attach Base Flashing: Custom-fit the flashing to the chimney's dimensions​​​​.
  • Add Step Flashing and Chimney Saddle: Install step flashing around the chimney corners and set the chimney saddle in place​​​​​​.
  • Install Cap Flashing: Secure the cap flashing in grooves cut in the mortar joints​​​​.
  • Secure and Seal the Flashing: Drive the flange into the mortar, secure the flashing with anchors, and apply caulk for sealing.


Regular maintenance and timely repair of chimney flashing are key to protecting your home from water damage.

Whether opting for a DIY approach or hiring a professional, understanding the process and requirements can help ensure a long-lasting and effective repair.

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