How to repair chimney flashing?

July 8, 2024
Avatar for Shakil AhmedShakil Ahmed
How to repair chimney flashing?

Chimneys may be an excellent addition to your home, adding warmth and charm and enhancing property value. When your chimney flashing is intact and functioning correctly, it keeps rainfall out of your home. However, it occasionally breaks or leaks.

The longer you wait to fix a leaky chimney flashing, the more damage your property will face. Leaks in your home can cause various concerns, including mold and other property damage. These problems can be costly to repair, so responding early and avoiding major harm is essential.

Depending on the level of the damage, one home’s damaged flashing may be able to be repaired, but another home’s flashing may require replacement. Contact Air Duct Now’s roofing professionals to find out what has to be done for your property.

Understanding chimney flashing

Flashing can be seen both around your chimney and on the surrounding roof. The primary aim of chimney flashing is to prevent rainfall from entering the homeowner’s property and causing leaks.

Flashing can be made of a variety of materials depending on the home. However, regardless of the material used for flashing, it must be waterproof. If the material is not waterproof, rain and moisture can easily penetrate the flashing and enter your home.

Typically, flashing is constructed of flexible fibres, sheet metals, or even plastic. This substance is applied alongside a compound to seal the flashing and prevent water from passing through.

Alternatively, if a chimney is not sealed, it can cause significant property damage. If there is rainfall outside, water may begin to flood into the resident’s home without a barrier to keep it out. This type of severe leak may result in wood rot. It may also attract insects or pests that are drawn to dampness, potentially resulting in infestations.

Signs your chimney flashing needs repair

Signs your chimney flashing needs repair

Properly installed chimney or roof flashing can survive for up to 30 years. Lifespan is governed by environmental factors such as where you reside, the shape and size of your chimney, and the materials used to construct it. Knowing the year your house was built can help you track the life of your chimney.

Signs that chimney flashing needs to be repaired include:

  • Leaking from within or outside the chimney.
  • Sounds and signs of dripping, like pools
  • Discolored bricks
  • Rust spots.
  • Water stains on interior ceilings or walls near the chimney
  • Visible holes in caulk around the flashing

Preparation for repair

Before you begin fixing your chimney flashing, make sure you have all of the necessary equipment and materials, and take key safety precautions.

Tools and material

  • Ladder (secure and stable)
  • Hammer
  • Pry bar or flathead screwdriver
  • Tin snips (for cutting flashing)
  • Caulking gun
  • Utility knife
  • Tape measure
  • Replacement flashing material (aluminium, copper, or galvanized steel)
  • Roofing nails or screws
  • Waterproof roofing caulk or sealant

Safety precautions

  • Ladder Safety: To access the chimney safely, use a strong ladder positioned on stable ground and securely extended.
  • Personal Protective Equipment: Wear gloves to keep your hands safe from sharp edges and goggles to protect your eyes from debris.
  • Weather Awareness: Avoid working on the roof during adverse weather to decrease the danger of slips and falls.
  • Roof Stability: To avoid accidents, make sure the roof is dry and sturdy before beginning work.

Steps to repair chimney flashing

Steps to repair chimney flashing 


Start by thoroughly examining the existing flashing surrounding your chimney. Check for visible damage, such as cracks, rust, or loose portions. Identifying these problems early will allow you to determine the scope of the repairs required.

Removal of old flashing

  • Remove Damaged Flashing: Use a utility knife to carefully remove any broken or rusted flashing. Make sure not to harm the shingles or the chimney itself. Remove all debris and old roofing cement from the area to provide a clean working surface.
  • Clean the Area: Use a wire brush to clean the area where the new flashing will be put. This step is critical to ensuring the new flashing adheres correctly and forms a watertight seal. Remove any debris, corrosion, or old cement altogether.

If you don’t clean the area, the new flashing may not adhere properly, allowing water to leak through and cause additional damage.

Installation of new flashing

  • Measure and Cut New Flashing: Measure the size of the locations where the new flashing will be put. Using these measurements, cut the sheet metal to the proper sizes. To prevent leaks, ensure that the parts fit snugly against the chimney and roof. It can be beneficial to cut the flashing slightly larger than required, since you can always trim it down later to ensure a precise fit.
  • Position the New Flashing: Place the newly cut flashing around the chimney, ensuring that they overlap properly to direct water away from the structure. Begin with the base flashing, then add step flashing along the edges, then end with counter flashing on top.

The current chimney flashing should serve as a reference for installation; however, if it is damaged, use the measurements from the previous step to determine ideal alignment.

  • Secure the Flashing: Use a hammer and nails to securely attach the flashing to the roof and chimney. Make sure to nail only around the edges to avoid causing extra holes for water to leak in. This process reinforces the structure and prevents mobility.
  • Apply Roofing Cement: Once the flashing is in place, use a caulk gun to apply a liberal bead of roofing cement along its edges and seams. Smooth it out with a putty knife to get a continuous, watertight seal. Roofing cement takes time to dry, so be patient and avoid moving or disturbing the newly equipped flashing.
  • Seal Joints with Roof Caulk: For further protection, use roof caulk to seal any flashing joints and edges. This phase is especially crucial where the flashing meets the chimney or in roof slopes, where water tends to gather. To apply roof caulk, load it into the caulk gun and carefully disburse it over the borders, smoothing it with a putty knife for an equal finish.

Testing and inspection

  • Final Inspection: After finishing the repairs, do a final examination to confirm that all flashing is securely in place and properly sealed. Look for any holes, loose portions, or missing locations in the roofing cement and caulk.

If you discover any problems, perform the necessary flashing repairs before moving on to the last stage.

  • Clean Up and Monitor: Clean up any waste or leftover materials from your workspace. It’s also a good idea to keep an eye on the repaired flashing in the coming weeks, especially after heavy rain, to make sure it stays waterproof. Annual inspections and maintenance can assist in preventing potential flashing concerns and keep your chimney in good shape.

Cost consideration

In some circumstances, simply resealing the flashing using polyurethane caulk, roofing cement, or another type of flashing sealer could fix the leak. This requires that the flashing is properly fitted and not bent or flared at the edges.

The cost of resealing the flashing around your chimney ranges from $150 to $425, depending on the size, type, flashing material, and roof type.

If your flashing needs to be replaced, the cost might range from $750 to $1450, depending on the chimney’s size, type, flashing material, and roof type. You must fix the issue as soon as you realize your flashing has to be replaced.

Final thought: Find an expert

Repairing and installing chimney flashing requires a significant amount of skill, work, experience, and care. You’ll need the correct tools and safety equipment, as well as precise measurements and knowledge. The process may also take longer than planned, leaving your roof and chimney vulnerable to more damage while you work on the restoration.

While you can fix the chimney flashing yourself, it is not simple. The best decision for you and your property is to call and set up an appointment with a professional like Air Duct Now. Our technicians can swiftly and safely replace your chimney flashing or notify you if more serious roofing issues exist.

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