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How To Fix a Leaky Chimney

Leaks are among the most dreaded roofing problems faced by most homeowners in Manchester and the UK. The damage from a leaky roof can be extensive and it is not uncommon to find an entire roof replaced due to the structural damage it predisposes the house to. The chimney, in particular, is often at risk of leaking. Some of the causes for leaks include worn out flashing, porous masonry among other reasons which we will go over in-depth in this article. We also look into different solutions to fixing a chimney leak.

Why does a Chimney Leak?

The chimney is a section on the roof which is often neglected by homeowners and some roofers alike. The chimney sits on the top of your roof, leaving it exposed to harsh weather conditions that wear it down and lead to leaks more often than other areas of the roof.

Reasons Your Chimney Might Leak and How to Fix Them

Improper or Wornout Flashing

How to Fix improper or worn out flashing

If the leak is a result of poor workmanship, then the flashing has to be redone depending on how bad it is and the materials used. It could be a simple case of redoing the flashing or finding long-lasting materials such as lead, which is very durable. Any small gaps can be sealed off using caulk or a good sealant.

Cracked Masonry and mortar joints

While the chimney is externally exposed to harsh weather conditions from the roof, it is also exposed to rising heat from the fireplace which damages the mortar joints and surrounding masonry. 


Often this does not happen in most chimneys but the heating and cooling take a toll on the mortar joints resulting in cracks through which moisture penetrates. 

In extremely cold weather, the moisture can expand making the crack expand or the masonry fall off. This process happens gradually but when a piece of stone falls off, the chimney is even more vulnerable to water penetration. 


Poor fixing of the mortar joints inside the chimney might be another reason the cracks develop. Again, when the masonry cracks, water seeps into the bricks, causing damp, which ultimately leads to a leak. 


This is why we emphasize roof inspections because a professional roofer can identify the moisture issue early on, preventing any serious problems down the line. 


Here are a few signs of a roof with damaged masonry:

  • You will notice the cracks on the bricks
  • The outer layer of the bricks might have chipped off
  • A leak in the chimney rather than the ceiling

How to Fix Cracked Masonry


Depending on the extent of the damage, the cracks might have to be caulked. If the bricks are heavily damaged and falling off, then a mason might have to repair and replace the brickwork.

Cracked Chimney Crowns

The chimney crown lies on top of the bricks and it houses the flue. Its other function is to protect the chimney masonry from winter elements such as snow and rain. Over the years, the chimney crown can deteriorate due to the expansion and contraction from the rising heat. Weather conditions such as long summer months and cold winter months can also result in expansion/contraction. As a result, the crown starts to crack and if it is not fixed on time, the chimney crown might have to be replaced.

How to Fix Cracked Chimney Crowns

Chimney crowns might not be very complicated to fix unless the damage is extreme. All it would take is cementing the chipped areas or taking off the current chimney crown and redoing it.


Rainwater will definitely result in a leak as it accesses the inside of your chimney. Having an open-ended chimney potentially results in damage to the interior walls when it rains. Your chimney is also exposed to other pests such as birds or bees that may find their way in and build a nest or a hive.

How to Fix Rainwater Leaks

The best fix for this is having a chimney cover in place. There are beautiful chimney covers in place and their installation is quite simple. The chimney cover has some gaps on the sides to allow smoke and flue gas to pass through.


With this, you now understand what causes leaks through the chimney and the possible fixes. While you might want to fix the leak yourself, we recommend leaving it to an experienced roofer with the requisite licenses and insurance to do the job. At Manchester Roofers we have been trusted as reliable roofers in Manchester over the years. We should be able to diagnose the problem and get to the root cause of your chimney leak.


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