The condition of your chimney is particularly important when it comes to roof health. Curb appeal, the safety of your building, and the overall value of your building all rest on the condition of your chimney.

If your brick chimney is crumbling and needs a repair, you should handle it right away, as more time passes the more damage will be.

It is important that your repair work is done exactly as the city code requires, otherwise you are going to have even more work ahead of you.

This article is designed to help you learn why your chimney is crumbling, how to prevent it in the future, and the best way to deal with it when it does happen.

Information, as always, is your best tool.

Crumbling brick chimney repair – What Causes Brick to Crumble

crumbling chimney brick repair 1

Exterior bricks are often exposed to the elements. This can mean that the water can be absorbed into the cracks and then freeze, causing the brick itself to crack.

It can be more common in poorly made bricks as they are less likely to be handled incorrectly during the creation process.

There is also a huge difference in façade brick and whole brick. Brick facades are thinner and have less bulk which means there is less room for the expanding of the brick itself.

Here are a few other common issues with brick chimneys:


Maybe the most common issue is bricks starting to crack. Beside the visual issue that’s just makes your home look in poor shape, it is actually a fire hazard.

It’s because when you use the fireplace, the smoke carries with it small waste particles that will end up being stuck in the cracks and building over time.

After a while, you will have a thick black layer covering the inside of your chimney, it will look something like this:

crumbling brick chimney repair
Image via jamesballchimney

When it reaches this level of waste thickness, even a small spark can start a chimney fire, because of something that is called creosote.

We won’t get into much details about this, you can read about it here. But for sure it’s a must fix.

Not so fun fact – There are actually over 61 fires that start everyday because of dirty chimneys in the US.


Water can cause real damage to your chimney, besides the obvious mold that will quickly add up, the most problematic issue with water is

crumbling brick chimney repairs

When you mix water with creosote it becomes acid. This will cause your chimney to become rustic and it will speed up the deterioration process of the bricks and mortar. 

Damaged Crown

The crown of the chimney is meant to prevent water damage and is built in a downward slope. It protects the part of the chimney from the connecting roof to the top.

damaged chimney crownImage via jamesballchimney

If your crown is damaged or broken, water will easily get in the chimney and will cause damage much quicker.


The roof flashings are there to piece together the chimney and the roof together so that no water can get in the home when it’s raining.

chimney repair bricks Image via youtube

A faulty flashing can be a real pain, if you need your flashings repaired. get in touch with a contractor ASASP.

Wrong Dimensions

You might be surprised to learn that most masonry contractors in Chicago are lacking the proper license to work with bricks and concrete.

This will cause problems to you the costumer as they will have a hard time getting the right permits when building or working on your chimney.

At Chicago Brick Co we hold both a class C and class B license from the city of Chicago so we can work with cement and bricks.

If you build the chimney too short, there’s a good chance it won’t be able to prevent downdrafts.

If you build it too short, there’s not enough room for the smoke to ” roll ” before entering the smoke shelf.

Chimney Caps

The most obvious thing to have working as it should. The chimney cap is there to prevent water from directly getting in the chimney and fireplace.

chimney brick repair crumblingImage via aircontrolsbozeman

It also helps keep leaves and other things you don’t want to fall inside your home through the chimney.

Leaning Chimneys

YES, it’s a big deal. If your chimney is leaning even just a little bit, it maybe a BIG problem as it’s in danger of collapsing and possibly hurting someone or cause more damage to your house.

That does not mean that it is always the bricks that cause the chimney to begin to crumble. 

When It is not the bricks fault

Even the best quality brick can fail. Most of the time it is due to the mortar used to hold the brick together.

Mortar is made of concrete, lime, and sand. It must be made exactly right. If it is too thick it can dry out and crack. If it is too thin, the brick will not stay in place.

The fact that it is very porous means that it can hold water. The temperature change that comes with the seasons can also mean the swell and contracting of the mortar.

This not only causes cracking, but it can also cause crumbling as the mortar denigrates.

How to prevent chimney crumbling brick and mortar

You can actually conduct a simple and quick visual chimney check up to help you determine if there’s something that needs to be fixed:

 1. You can first have a look at your fireplace hearth and see if there are crack or broken bricks.

2. Check the firebox for visually broken bricks or cracks.

3. Make sure to check the damper to see if it works with no issues.

4. Go outside and look at the chimney to see if you have cracked bricks or even broken ones.

5. Make sure to repair the bricks before you continue to use the fireplace to stop the damage from escalating. 

The absolute best way to prevent crumbling is to do a weather seal on the outside of your brick. This will keep the mortar from absorbing water.

The expansion caused by water absorption can be one of the most damaging of all the problems.

You will still have the expanding and contraction with the weather, but this is natural. You will even find it in wood.

However, when water is absorbed, it can create a decomposition of the mortar. The sand can wash away when the water runs out or upon contraction.

During the cold months, water can turn to ice which can destroy both brick and mortar.

As soon as your chimney on the roof is repaired, you will want to have it weather treated with a seal that will allow the water to run off it completely rather than be soaked in.

This will save you time and money while increasing the life of your brick chimney.

It is not always done automatically so you will want to make sure you tell your local chimney contractor that you want it done.

How to decide if your brick chimney needs repair

If you have your chimney maintained regularly, either by a contractor or on your own, then you will know exactly when to have it fixed.

Faulty chimneys are the cause of sixty house fires per day. The cracks can hold a buildup of creosote.

This creosote can ignite with one simple spark. It can be made worse with water.

Visually looking up at your chimney is not enough. Of course, if your chimney is tilting, bricks are falling off, or you can see cracks from the ground, then you know it needs to be repaired.

Not all repairs are that obvious. You will want to have it inspected seasonally. You will also want to have it cleaned thoroughly so that you can see what needs to be done prior to your first fire in your fireplace.

It is also a good idea to have your chimney inspected for animal nests. Birds can do a lot more damage than you might think.

They can chip away at bricks and mortar to make room for their nest. Squirrels looking for somewhere to store their food can also do unseen damage.

The Chimney Repair – DIY

It is completely possible for you to do minor repairs to your crumbling brick chimney yourself.

You will need to make sure that your roof can hold you before you climb on, safety first. Then you can use a chisel to break away the old mortar.

Sliding out a single brick is easy once you break the old mortar off and away. Then simply slide out the broken brick. Replacing the mortar is not hard.

It is time consuming. You will need to have to use a chisel to remove all the old mortar. Then you can use a trowel to smooth the new mortar in place.

Finally, you can slip the new brick into place. It is especially important that you replace each broken brick, remove all crumbling mortar, and replace it with fire proof brick and mortar.

Broken Chimney Repair – When You need a contractor

There are times when you should not do the work yourself. These are times when it is dangerous or when the damage to your chimney is unknown.

If you are just buying a property, have the chimney inspected and cleaned. If you can see that there are more bad bricks than good ones or that all the mortar is crumbling and unable to hold the bricks in place, it is best to go ahead and let a contractor come in and do the work.

There are benefits to allowing a contractor to do the work:

  • You will get a warranty.
  • • You will be able to get a contract for maintaining it as well as repair it.
  • • You can be sure that any animal debris will be properly removed as well.

Your chimney is one place where you can be sure to increase the value of your home.

You will never regret the choice of repairing your crumbling brick chimney and to make sure your family and property are safe.