Damp Chimney

How To Fix A Damp Chimney Breast?

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Key Takeaways:

  • Addressing Damp Chimney Breast: The content emphasizes that a damp chimney breast can pose both aesthetic and structural challenges, including water stains, unpleasant odours, and potential health hazards.
  • Signs and Causes of Damp: Damp on a chimney breast is described as evident through visible water stains, musty odours, and the growth of mould and mildew. The causes of chimney damp can vary, encompassing issues within the chimney structure, poor ventilation, and external sources.
  • Consequences of Untreated Damp: The content underscores the serious consequences of leaving damp on a chimney breast untreated. It can lead to structural deterioration of the chimney, resulting in significant repair costs.

A damp chimney breast can be a frustrating and potentially hazardous problem to deal with. Not only can it cause unsightly water stains and unpleasant odours, but it can also lead to structural damage and health issues if left untreated. 

If you’ve ever fallen into such problems, a question may arise: how to fix a damp chimney breast? Fortunately, you can take some simple steps to fix damp on the chimney breast and prevent it from recurring. 

You’ll just need to identify the source of the damp, repair any damage to the chimney, and install a damp-proof course to prevent moisture from entering.

In this guide, we will provide you with an outline of the steps needed to identify the source of the problem, address the underlying issue, deal with the effects of the damp, and prevent future issues.

What Does Damp on Chimney Breast Mean?

Damp on a chimney breast refers to moisture or water in the area surrounding the chimney. This can manifest as visible water stains, musty odours, or even the growth of mould and mildew. 

Damp on Chimney Breast

Typically, damp in the chimney breast can occur for various reasons, including issues with the chimney itself, such as cracks or leaks, poor ventilation, or water ingress from external sources such as a damaged roof or broken or blocked gutters. 

If left untreated, damp on a chimney breast can lead to more serious problems such as structural damage, erosion of masonry, and even the potential for dangerous chimney fires. Therefore, it’s important to address the issue as soon as possible to prevent further damage and ensure the safety of your home.

Why Damp On Chimney Breast A Problem?

Damp on chimney breast is a problem for several reasons. Firstly, the damp leads to the deterioration of the chimney’s structural integrity, which is costly. 

Secondly, the external moisture formed due to chimney damp creates an environment for mould and mildew growth, which cause health problems for those living in the house, especially those with respiratory issues. 

Finally, the damp causes a musty smell that is unpleasant and difficult to remove. Therefore, addressing a damp chimney breast as soon as possible is important to prevent further damage and potential health hazards.

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Common Causes Of Damp On Chimney Breasts

Homeowners should be aware of several common causes of damp chimney breasts. Here we’ve talked about some major causes of damp issues on chimney breasts. 

Damaged Flashing 

Flashing is a thin strip of material, usually made of metal, installed around the base of the chimney where it meets the roof. It helps to prevent water from entering the chimney and causing damage to the roof and walls. Flashing can become damaged or deteriorate due to exposure to the elements.

Damage in flashing cause water to seep through the gaps and enter the chimney, leading to a damp chimney breast.

Cracked Chimney Stack 

The chimney stack is the vertical part of the chimney that extends above the roofline. It is exposed to the elements and subject to weathering, which causes it to crack or deteriorate over time. When a chimney stack is cracked, water seeps through the cracks and enters the chimney, resulting in damp and water damage, causing a damp chimney breast.

A cracked chimney stack mortar is also a safety hazard if it becomes unstable or collapses. It happens especially during wet weather when mortar joints become waterlogged and starts to erode.


Leaks are another cause of a damp chimney breast. This mainly occurs in various ways, such as from damaged flashing, cracks in the chimney, or damaged chimney caps. Allowing water to enter the chimney leads to damp, mould, and other water damage.

Damp patches will typically appear on the ceiling and walls of the room below, and repair work is needed to fix any underlying damp problems.

Rising Damp

Rising damp in your chimney is another possible cause of a damp chimney breast. This occurs when moisture from the ground is absorbed into the walls of a building, and it affects any part of the structure that comes into contact with the ground.

In the case of a chimney breast, rising damp can occur if the chimney stack or flue is not properly sealed, allowing moisture to seep into the masonry and cause damp.

What Are The Symptoms Of Damp On Chimney Breast?

Symptoms Of Damp On Chimney Breast

Damp on chimney breast causes a range of symptoms that indicate a problem with your chimney. Here are some common visual signs of a damp chimney breast.

  • Water Stains: Water stains are a common symptom of a damp chimney breast. When water enters the chimney, it seeps into the surrounding masonry, causing discolouration and staining on the walls and ceiling around the chimney breast.
  • Musty Odours: When water enters the chimney, it creates a damp and humid environment that leads to the growth of mould and mildew. This causes musty odours that are often noticeable around the chimney breast area.
  • Peeling Wallpaper Or Paint: Peeling wallpaper or paint is another symptom of a damp chimney breast. Water entering the chimney runs into the walls and ceiling around the chimney breast and causes the wallpaper or paint to peel or bubble.
  • Crumbling Plaster: Water enters the chimney, escapes into the walls and ceiling around the chimney breast, and causes the plaster to become soft, crumbly, and weakened.
  • Damaged Brickwork Or Masonry: Source of damp damage to the brickwork or masonry of the chimney stack, which may be visible on the property’s exterior.

How To Inspect Chimney To Identify The Cause Of The Damp?

Inspecting the chimney is the first step in identifying the cause of the damp. Here are the steps you have to follow to identify the causes of damp on the chimney breast. 

How To Inspect Chimney
  1. Examine The Exterior Of The Chimney: Start by inspecting the exterior of the chimney for signs of damage, such as cracks in the brickwork, missing or damaged mortar joints, or damage to the chimney cap. Look for any areas where water might be able to enter the chimney.
  2. Check The Flashing: Examine the flashing where the chimney meets the roof. Look for any damage or signs of wear, such as cracks or missing pieces. Ensure the flashing is sealed tightly against the chimney and the roof to prevent water from entering.
  3. Inspect The Chimney Crown: The chimney crown is the top part of the chimney stack that covers the flue. So, check for any cracks or damage to the crown, which allows water to seep into the chimney.
  4. Look For Signs Of Internal Walls: If the chimney’s exterior appears in good condition, the damp may come from inside the chimney. In that case, you have to look for any signs of damp or water damage on the walls and ceiling surrounding the chimney.
  5. Use A Moisture Meter: damp can be inside the chimney, so you should use a moisture meter to test the moisture level in the walls. This will help you to determine the extent of the problem and identify the source of the damp.

Materials And Tools Needed To Carry Out On Damp Chimney Repairs

Materials And Tools Needed To Carry Out On Damp Chimney Repairs

The materials and tools needed to carry out repairs on a damp chimney breast will depend on the specific problem that needs to be addressed. Here are some of the common materials and tools you may need:


You will need to purchase new flashing material to repair or replace the flashing around the chimney. The type of flashing you need will depend on the type of roof and chimney you have. Common flashing materials include aluminium, copper, and galvanized steel.


To repoint the brickwork, you will need to purchase mortar. The type of mortar you need will depend on the type of brickwork you have. Different types of mortar you’ll find, like Portland cement and lime mortar.

Chimney Cap

To install a chimney cap, you will need to purchase a cap that is the correct size for your chimney. A chimney cap is made of stainless steel, copper, or aluminium.


You need to use a dehumidifier to dry the area for damp chimney breasts. Dehumidifiers are available in various sizes and can be purchased at hardware stores.


Some tools you may need include a hammer, chisel, trowel, wire brush, and caulking gun. You may also need a ladder, depending on the chimney’s location.

How To Fix Reasons For Damp On Chimney Breast?

Once you have identified the underlying cause of the damp in the chimney breast, you’ll need to take the necessary steps to fix the issue. Following are the steps you need to take:

How To Fix Reasons For Damp On Chimney Breast

Step 1: Repair Or Replace Damaged Flashing

Repairing or replacing damaged flashing is the most effective fix for a damp chimney breast. Flashing is a waterproof metal material installed around the base of a chimney to prevent water from entering the home. 

If the flashing is damaged, water can seep into the chimney breast and cause moisture problems. Replacing or repairing the flashing will help to stop the moisture from entering the chimney breast, thus eliminating the source of damp.

Step 2: Repoint The Brickwork

Repointing brickwork involves removing the existing mortar between the brickwork, cleaning the area, and then replacing the mortar with new mortar. The new mortar must be waterproof and applied in layers no more than 1/2 inch thick. 

The mortar should be applied with a trowel and left to dry before being pointed with a pointing trowel. Once the pointing is complete, the area should be sealed to help protect it from moisture.

Step 3: Install A Chimney Cap

A chimney cap is one of the easiest and most effective ways to prevent damp on the chimney breast. It fits directly onto the top of the chimney and helps to keep out rain water, snow, and birds and animals from entering. 

It also helps keep warm air from the fireplace or stove from escaping the chimney. Installing a chimney cap is a simple DIY job that can be accomplished in an hour or two. 

Step 4: Drying Out The Affected Area

The best way to dry out a damp chimney breast is to remove any sources of moisture, such as condensation, leaks, hygroscopic salts and other water sources. Once the sources of moisture are eliminated, the chimney breast should be allowed to dry out naturally. 

However, if this does not work, a dehumidifier can speed up the drying process. Additionally, fans may be used to help circulate air and aid in the drying process.

Step 5: Removing Mold And Mildew

If mould or mildew has developed, it will need to be removed using a solution of bleach and water or a commercial mould and mildew remover. To remove mould and mildew as a fix to a damp chimney breast, you should wear protective gear and mix a solution of water and mild detergent. 

Apply the solution to the affected area, scrub with a brush, and then rinse with clean water. Afterwards, dry the area thoroughly and ensure proper ventilation to prevent future growth. If the mould is extensive or difficult to remove, seek professional help.

Importance Of Following Appropriate Safety Procedures

When fixing a damp chimney breast, you should follow appropriate safety procedures to prevent accidents and injuries. Here are some safety tips to keep in mind:

  • Use Appropriate Safety Gear: Wear appropriate safety gear, including gloves, safety glasses, and a dust mask, when working with mortar or other materials. You should use a safety harness on the roof or a ladder.
  • Work With A Partner: Working with a partner to hold the ladder, hand you tools, and assist is safer.
  • Be Aware Of Power Lines: When working on the roof tiles, be aware of nearby power lines and ensure that your ladder or tools do not come into contact with them.
  • Use Appropriate Tools: Use appropriate tools for the job and ensure they are in good condition. Do not use damaged or worn tools in the chimney pots.
  • Follow Manufacturer’s Instructions: Follow the manufacturer’s instructions when using materials such as mortar, flashing, or sealant. Make sure you understand how to use the materials correctly and safely inside a chimney pot.
  • Take Breaks: Take frequent breaks to prevent exhaustion and dehydration, especially when working in hot or humid conditions.
  • Consult With A Professional: If you are not comfortable carrying out the repairs yourself in your broken chimney pots, it is best to consult a professional.

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How To Repair Any Damage Caused By Damp

How To Repair Any Damage Caused By Dampness

It’s time to repair any damage that has been caused already. Here are some steps you need to take to repair the area:

1. Remove Damaged Materials

To repair any damage caused by damp in a chimney breast, you should identify and remove the damaged materials that have been affected, such as plaster, drywall, or wood. 

Cut out and remove the damaged areas, ensuring that the surrounding area is dry and free of mould. Once the area is clean and dry, it can be repaired by replacing the removed materials with new ones, such as plaster or drywall.

2. Re-plaster 

You need to re-plaster the affected area to repair damage already done by damp on chimney breast. After removing any damaged materials, ensures the area is dry and free of mould. Then, apply a waterproof sealant to the area, and allow it to dry completely. 

Next, apply a coat of plaster to the area, smoothing it out with a trowel. After it dries, apply a second coat of plaster if necessary. Sand the surface of the plaster and repaint the area as needed. It’s important to address the root cause of the damp to prevent further damage.

3. Repaint

After removing any damaged materials, allowing the area to dry and free of mould, and re-plastering if necessary, you need to repaint the affected area to repair any damage caused by damp in a chimney breast. You should use paint that is designed for use in damp areas to prevent future problems. 

4. Apply A Damp-Proof Membrane

If the damp was caused by rising damp, you must apply a damp-proof membrane to the affected area. Damp-proofing will prevent moisture from seeping through the walls and causing further damage. Follow the manufacturer’s instructions carefully when applying the membrane.

5. Inspect Regularly

After the repairs have been completed, it’s important to inspect the area regularly to ensure that the damp has not returned. If you notice any signs of damp, such as a musty odour or water stains, address the issue immediately.

How To Maintain The Chimney To Prevent Future Issues?

Maintain The Chimney To Prevent Future Issues

Maintaining your chimney is essential to preventing future issues and ensuring the safety of your home. Here are some tips for maintaining your chimney:

  • Regular Cleaning: Have your chimney cleaned regularly to remove soot, debris, and other materials that contribute to damp and other issues. A professional chimney sweep should be able to carry out thorough cleaning.
  • Install A Chimney Cap: As mentioned before, installing a chimney cap will prevent water, debris, and animals from entering your chimney.
  • Check For Cracks Or Other Damage: Regularly inspect the exterior of your chimney for cracks, damage, or other signs of wear and tear. These are signs of more serious issues that need to be addressed.
  • Keep The Surrounding Area Clear: Ensure the area around your chimney is clear of leaves, branches, and other debris that could catch fire.
  • Use The Right Fuel: Only burn dry, seasoned wood in your fireplace or wood stove. Burning wet wood cause excessive creosote build-up and other issues.
  • Use Your Fireplace Properly: Use your fireplace or wood stove only as intended and avoid overloading it with too much wood or other fuel. It will cause excessive heat and damage to your chimney.

Final Words

Fixing damp on chimney breast is a challenging task, but it’s essential to ensure the safety and health of your home. Hopefully, you’ve figured out how to fix a damp chimney breast after reading the above discussion.  

By following the steps outlined above, you can identify the cause of the damp, carry out repairs, install a bridged damp proof course and take steps to prevent the recurrence of the problem. 

Remember to prioritise safety during the repair process and when maintaining your chimney in the future. Regular maintenance and care allow you to enjoy a safe, healthy, and well-functioning chimney for years to come.

Picture of Jake Fitzgerald - Damp Surveyor

Jake Fitzgerald - Damp Surveyor

Surveyor of Timber & Dampness in Buildings (CSTDB) & ( MRICS ) Chartered Quantity Surveyor

Jake is a qualified chartered quantity surveyor and experienced damp specialist with a unique skill set in thermal imaging. With a focus on effective solutions, Jake combines his expertise in quantity surveying and thermal imaging to accurately assess and address damp-related issues. He utilises advanced technology to identify hidden moisture sources and develop targeted strategies, ensuring comprehensive and cost-effective solutions for his clients. With a commitment to open communication and client satisfaction, Jake delivers cutting-edge solutions that tackle damp challenges head-on.

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