Home » blog » How to Repair Chimney Bricks?

How to Repair Chimney Bricks?

Leaving cracks in bricks unrepaired is detrimental to a chimney’s durability. Patching up cracks in your bricks as they appear saves you from that tonne of expenses that a damaged chimney would bring.

You also get to keep your household safe when you repair your brick chimney as possibilities of chimney fires get reduced.


An interesting fact about these cracks in brick chimneys is that they tend to increase over time. A little crack in the summer can become massive by winter.

Leaving these little cracks unrepaired paves way for rain, ice, and insect penetration. Water destroys bricks when it finds its water into them so you must always make sure they don’t find their way into your bricks by repairing cracks immediately they show up.


Before we go into details on how to repair chimney bricks, let’s discuss a major reason why chimney repairs are needed.

Why Should You Repair Cracks in Brick Chimneys?

Chimney fires are like explosions. Once a chimney fire starts, normal home fire extinguishers can’t quench it. The fire department must intervene to quench the fire. Why experience chimney fires when you could have just repaired the crack?

Moving on, let’s discuss how to repair chimney bricks the right way. 

Repairing a Brick Chimney

You can’t carry out a proper repair without the right tools and materials. Here are the tools and materials needed for an outstanding brick chimney repair:


  • Ladder
  • Hammer
  • Pointing trowel
  • Paintbrush
  • Tuckpointing tool
  • Masonry chisel
  • Joint raker
  • Putty knife
  • Caulk gun


  • Latex gloves
  • Mortar
  • Water-based silane
  • Safety glasses
  • Clean rags
  • Sure Klein
  • High heat mortar


Once you’ve all these tools and materials in place, follow these step-wise producers for a successful repair:

  • Step 1 – Repointing the Mortar: Every chimney brick has a mortar and repointing a brick’s mortar means replacing the existing mortar with a new mortar.

    To repoint a brick’s mortar, make use of a joint rake to scrape the existing mortar off the brick. After scraping, spray down the brick with a hose and leave the setup for half an hour.

    While you wait, prepare your new mortar. After half an hour, use a pointing trowel to press down your new mortar into the open joints of your brick.

  • Step 2- Sealing gaps: With a caulk gun, you can seal up gap founds at joints in bricks (the chimney glue and the crown).

    The crown of a chimney is the concrete cap that shields the top of the brick used for the chimney. Alongside a caulk gun, you will also need a high-heat mortar, and a wire brush (to clean joints), to seal up gaps at joints. Ensure you seal the joints perfectly to prevent penetrations.

  • Step 3- Patching up cracks: Cracks in the chimney can occur in the large crown or hairline area of the chimney. You can patch large crown cracks with pre-mixed cement, all you need to do is inject the mixture into the crack area and let it cure for four to six hours. For hairline cracks, make use of water repellents to seal the cracks as they will penetrate the hairline easily.

  • Step 4- Final repair: Depending on how severe the damage is, you can decide to either repair or replace a chimney brick.

    For repair, you could make use of a high-heat mortar and a caulk gun. To make repair excellent, always make sure you scrape off all existing mortars completely before applying your repair mixture.

    For replacement, you can effectively remove a damaged brick without causing any further damage by using a masonry chisel. After replacement, always make sure to smoothen the brick’s surface using a tuckpointing tool.

Summing Up 

The weather is a major cause of chimney brick’s cracks, but inadequate maintenance makes the brick’s damage worse. Chimney brick cracks isn’t a joke as it could end up causing a fire outbreak that could claim people’s lives. 


Finally, always make sure to check your chimney for brick cracks and carry out repairs when necessary, this keeps you and your family safe.


Table of Contents