Every chimney built never lasts a lifetime.

In other words, the action of weather on the structure steadily weakens the structure. This is especially true for masonry chimneys which require scheduled maintenance to remain in good shape.

Crumbling Brick Chimney Repair Options

Here, we’ll be looking at one of the conditions of disrepair and the processes involved in fixing it. So, do you have a crumbling chimney? You’ll want to find details on how to go about the process of getting it fixed.

Chimneys should never be left unattended for too long. To remain functional and last longer, you’ll need to carry out more maintenance work.

What Leads to Chimney Brick Spalling?

When a masonry chimney is newly built, its condition is in top shape and it’s expected to have a significant lifespan. In most cases, well-built masonry chimneys should last for as long as your home lasts.

However, due to exposure to the elements or harsh weather action, a lot of deterioration is witnessed.

One of the most common types of deterioration is spalling bricks. What’s this about? For those who don’t know, this is simply a process whereby brick surfaces flake off.

This continued action, when left unchecked could result in major damage as the resistance or pressure absorbing capacity of the chimney stack decreases.

With the details supplied above, you should be able to take immediate action to address any deterioration.

Knowing the Underlying Issues

Whenever you notice a chimney crumbling or spelling, it’s important to know the underlying reasons for its deterioration. Now, moisture is a well-known cause for crumbling chimneys.

However, it isn’t the only factor responsible.

Temperate regions have very low temperatures that contribute to masonry chimney deterioration. So do leaky roofs and gutters. What more?

The inclusion of older or salvaged bricks in chimney construction could also contribute to its crumbling. If you’ve used a pressure washer before, you might have damaged the structure.

  • Temperate Climatic Conditions

One thing that’s common with all temperate climates is the freeze and thaw cycles that occur with moisture in bricks. When moisture in chimney brick freezes due to cold weather conditions, it expands, thus altering the structure of the brick.

As temperature increases, it thaws. This continued cycle (freeze-thaw) leads to a weakening of masonry chimneys, thus resulting in crumbling or spalling of bricks.

Immediate repair actions will need to be performed to prevent further deterioration of the chimney.

Freeze-Thaw Cycles And Spalling

According to the Chimney Safety Institute of America (CSIA), the freeze-thaw process that’s common with porous masonry materials occurs when moisture is absorbed.

Due to the porous nature of unprotected bricks and mortar, moisture gets in when it rains.

The moisture present in such bricks gets frozen when the temperature drops to about 32 degrees Fahrenheit. This thaws with a temperature rise.

The continuous freeze-thaw cycles that unfold result in an expansion and contraction within masonry material.

This continuous expansion and contraction ultimately lead to flaking off or spalling of chimney bricks. An urgent fix is needed to address this problem and prevent it from worsening.

With prolonged neglect, your chimney structure is likely to collapse. This isn’t something you want for your chimney.

  • Leaky Roofs & Gutters

This problem is also moisture-related.

When roofs or gutters leak, they let in water which is absorbed by the building’s structure. This is soaked in ad steadily weakens. When conditions such as freeze-thaw cycles are added, deterioration becomes rapid.

Leaky areas on the roof or gutters must be fixed immediately to address the problem before it worsens.

  • Inclusion of Salvaged Bricks

Salvaged bricks from other structures are sometimes used for chimney construction. While such construction materials may seem to be in good shape, they aren’t. Wear and tear are likely to have already set in.

So, when used for chimney construction, it won’t be long until deterioration sets in.

Although salvaged construction materials such as bricks can be repurposed, they shouldn’t be used for building a chimney because they’re already porous.

It’s easier for moisture damage to happen with salvaged bricks than it is for chimneys built with new bricks. When the condition of the exterior brick is in bad shape, it’s easier for such to absorb water.

Spalling sets in much sooner than it would for newer brick chimneys. Spalling is only one part of the likely issues caused by salvaged bricks.


Such bricks wouldn’t withstand weather conditions that much. The result is a crumbling or spalling chimney.

Here, any maintenance work performed on the chimney structure would be short-lived as the porous nature of bricks will mean more moisture penetration.

With freeze-thaw cycles, such condition is worsened.

  • Use of High-Pressure Equipment on Masonry Chimney

There are times when rooftops will need to be cleared of moss, algae, mold, mildew, and lichen. This cleaning action may be extended to the chimney stack.

When this happens, there’s significant deterioration of the brick surface. This is worsened when freeze-thaw cycles are already taking place.

Not all bricks have the same levels of density. While some bricks are dense through and through, others are only dense on the outside while their core is softer.

Porous bricks are worse as they easily crumble or flake off when high-pressure cleaning is performed.

An easier way to address this problem is to avoid high-pressure cleaning to preserve your chimney.

Irrespective of whether sand or water is used for such, pressure cleaning erodes the surface of bricks, thus leading to all sorts of problems.

Under normal circumstances, chimney brickwork would have waterproofing sealant.

This sealant keeps out water from getting in. However, when machinery like sandblasters or a pressure washer is used for removing dirt off of brickwork, it strips off the protective layer or waterproofing.

  • Using Non-Breathable Sealants on Chimney

Sealants are vital to preserving masonry chimneys from moisture presence. While this is true, there are good as well as bad sealants.

A non-breathable sealant is an example of a bad sealant and shouldn’t be applied or used on a chimney. So, how does this affect the chimney? Shouldn’t moisture be kept out?

Well, that’s true. However, brick masonry has its natural breathing characteristics. Here, water is absorbed and released through certain pores.

When non-breathable sealants are used, this natural breathing action is obstructed. So, water gets trapped within the chimney with nowhere to go.

The result is a weakening or spalling brick. Any of these problems are likely causes for spalling bricks.

  • Water

All the causes discussed above are water-related. It’s easy to see why. Being the exposed component of the chimney system, the stack gets or receives all the harsh weather action.

This includes rain, freezing temperature, and so on. The steady hit received from rainfall causes brick degradation.

Another way chimney bricks are likely to spall is when drainage or gutter isn’t well constructed. Constant spills or splashes from rainfall steadily degrade the chimney brick. What more?

There may be the absorption of water via vapor in addition to wet soil that travels up the chimney structure.

All of these conditions expose the chimney brick to spalling.

Before long, the brick begins to flake off or deteriorate. Like the others mentioned earlier, not addressing the problem on time could cause your chimney to crumble.

Equipment & Supplies Needed For Crumbling Brick Chimney Repair

Certain tools are basic to spalling brick repair.

These include cold chisel, mortar, club hammer, water, sharp trowel, and waterproof sealants. Others are replacement bricks, drills, and 6 to 8mm masonry bits.

With these obtained, you’re ready to proceed with the repair.

Spalling Brick Chimney Repair Guide

Addressing underlying causes of crumbling brick chimneys is central to the comprehensive resolution of the problem.

Here, the aim is to find out or establish how moisture gets into the masonry in the first place. Just going ahead with fixing visible areas of spalling will only be a cosmetic approach that achieves little.

Before long, the problem returns and even worsens.  You want to perform a more detailed and thorough repair work that gives a more permanent solution.

Several measures can be taken to resolve spalling brick issues on chimneys. If you prefer the DIY option, then you’ll basic tools like a cold chisel, club hammer, drill, sharp trowel, and masonry bit.

Others include replacement brick, mortar, and water.

Having obtained the above tools, you need to assess the problem to find out the root cause. Spalling could be a result of a leak.

By fixing the leak, you’re making it less likely for the same problem to happen again.

Removal and replacement of spalling bricks is the next action to take. This should be carefully done with about 3 to 4 bricks taken or removed from the wall at a time.

Get such bricks replaced with solid bricks. You’ll need to mix your mortar to hold the new bricks in place.

These are the causes and solutions for spalling chimney brick.

If the details supplied above seem like a lot of work, it’s best to call for professional help.

How To Repair Spalling Bricks On Chimney

A certified chimney sweep will have to be called to perform an inspection.

This inspection identifies the root cause of the problem as well as how extensive such damage is and how best to resolve it. When it comes to repairing crumbling brick chimneys, two scenarios always play out.

Your crumbling masonry chimney may be in its early or late stages.

i. Fixing Early Brick Masonry Chimney Spalling

At its early stages, crumbling brick chimneys aren’t as severe and have only begun to develop. This might be noticed by chance or when an inspection is of the chimney is being performed.

When this is noticed, it’s best to take urgent steps to fix such problems as failure to do so will lead to further deterioration.

So, how’s the process performed? It isn’t complex at all. Here, the damage mostly consists of small cracks on masonry. What’s needed at this point is the treatment of the brickwork and crown.

In most cases, chimney technicians use waterproofing sealants to have affected areas covered.

However, this approach isn’t universal. In other words, your crumbling brick chimney situation will need to be inspected to determine what approach best fixes the problem.

After applying a sealant to the spalling brick, the need for a new chimney cap may be necessary.

ii. Fixing Late Stage Masonry Chimney Spalling

Here, it’s obvious that brick spalling or crumbling has worsened and requires urgent fixes.

This is mostly the case when chimney inspections aren’t frequent, thus leading to the steady degradation of the structure. The brickwork may have to be repaired or the chimney completely rebuilt.

  • Repairing or Replacing Brickwork

Damaged or crumbled bricks need to make way for new ones.

Having them replaced helps reinforce the masonry chimney structure. Using your cold chisel and club hammer, gently chisel out or scrap the mortar surrounding the brick to make way for easy removal of the crumbled brick.

The drill and drill bit may come in handy when faced with challenges removing the bricks. With the brick removed, what remains is to have it replaced with a new one.

Of course, you’ll need to get one that’s identical to those used for the chimney construction.

Also, the removal of bricks has to be done one brick at a time. Getting too many crumbled bricks removed before replacing them with new ones may affect the chimney’s structural integrity.

Now, dampen the area before applying new mortar with your trowel.

Now, gently slide your new brick into space before dressing up the area to ensure the mortar is uniform.

  • Severe Damage Requires Rebuilding the Masonry Chimney

In cases where there’s severe damage or crumbling of your chimney brickwork, what’s needed is an overhaul of the structure. Here, a teardown and rebuilding of the chimney would be necessary.

Crumbling Brick Chimney Repair Cost

Chimney spalling repair costs between $200 – $700 depending on the rebuild or replacement options recommended.


Brick spalling is common with masonry brick chimneys that aren’t well maintained. Here, maintenance or the lack of it is a key determinant of whether spalling occurs or not.

Several conditions can be pointed out as being responsible for spalling chimney bricks.

The most common of these causes include the use of salvaged bricks for chimney construction and thaw-freeze cycles due to moisture presence.

Other causes of spalling include water, high-pressure cleaning, the use of non-breathable sealants, and improper brick placements.

These are the basic processes that apply to fixing crumbling brick chimneys. This shouldn’t be performed as a DIY project. Rather, getting expert help will be necessary.

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