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How to Repair a Chimney Stack

Every chimney setup has a stack. The chimney stack is the part of the chimney visible above the home roof.

It’s located very close to the chimney breast which is visible below the roofline. The main function of a chimney stack is to shield the chimney against products of combustion, directing such products into the atmosphere rather than your home.

Due to exposure to all sorts of air pollutants, stacks are prone to dilapidation in a short period and this is why you have to examine them frequently to prevent chimney damage.

Once a crack appears and it’s not repaired or replaced, the crack would expand and this will cause damages to joints and the whole chimney.

The major causes of chimney stack cracks are bad weather conditions and freezing water. Freezing water further aids the expansion of stack cracks when they gain entry into them. You will learn how to repair a chimney stack as you keep reading.

Why is a Chimney Stack Needed?

The parts of the chimney stack that weather is the “pointing found in the brick-wood” and the “flaunching located directly on top of the stack”. 

The stack’s flaunching has two basic functions, to keep the chimney pot firm and prevent rainwater from damaging the chimney stack. It’s designed like a steep pitch, this makes it easier to accomplish.

The flaunching’s function makes it suffer cracks frequently and these cracks always happen around the chimney and where the flaunching connects with the brickwork.

The flaunching of chimney stacks needs repair or replacement immediately after these cracks are noticed. The repair/replacement prevents the chimney stack’s exposure to rainwater and debris.

The pointing in the brickwork has just one major function, to hold the chimney joints firmly in place. Just like the flaunching, pointing in the brickwork is also prone to dilapidation over time.

The pointing in the brickwork needs rapid repair and replacement to keep the chimney joints firm and rigid.

Photo by Bru-nO on Pixabay

Repairing a Chimney Stack Effectively 

Just as discussed earlier, the “flaunching found at the top of the stack” and the “pointing in the brickwork” are the major parts of a chimney stack carrying out the stack’s basic functions.

With this, you would expect these major parts to suffer the most damages that happen to the chimney stack. How then can you carry out replacement and repair on these two major parts of chimney stacks?

The best way to go about flaunching damage is through replacement. To replace a failed flaunching, you have completely got rid of the failed flaunching using a chimney repair tool called – wire brush.

After clearing the failed flaunching area, you can then carry out its replacement using grit and cement or mortar (lime-based) depending on your budget as the homeowner.

For the pointing in the brick, the best way to go about its repair is the full replacement of the brick. Sealing up bricks will only give temporary comfort so replacement is the best. 

With the chimney stack relaunched and repainted, its ability to resist bad weather conditions and prevent debris from entering the chimney will be restored.


Here are some tips of how to repair a chimney stack:

  • Around joints, make sure you use long-lasting lead as it’s the best item of waterproofing
  • Avoid using cheap glass-reinforced plastics or cement strips for your flashing repair
  • For loose flashings, keep them firm with fresh mortar or create a new stepped line on the chimney’s side, fix the chimney into the opening, then keep the setup sealed


Chimney stack repair/replacement needs effective planning to ensure the rigidity and structural firmness of the chimney is maintained. The article above explains what part of the chimney stack you should concentrate on during repair and how you can go about the repair effectively.

Follow the National Fire Protection Association (NFPA) of repairing your chimney every 12 months and your chimney stack will also be in good shape. 


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