Crack in Fireplace: How Dangerous Is It?

Crack in Fireplace: How Dangerous Is It?

Most people expect their fireplace to last for decades. But sometimes it happens that a crack in fireplace can disrupt those plans. Today, we’re going to look at why firebox cracks happen and how to deal with them before they lead to serious fire hazards and carbon monoxide poisoning.

What Causes Fireplace Cracks

To begin with, the damage in firebox appears very slowly, with barely noticeable hairline cracks. Admittedly, inspecting a refractory mortar or its fireproof panel is not part of our daily routine. So, over time, the minor gaps get bigger and bigger.

Hopefully, the cracks you see in your firebox are still fixable. Below we will point out which cracked fireplace refractory is considered repairable. Stay tuned to learn all about firebox repair methods!

Why repair a crack in fireplace
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Normal wear and tear

No matter how well-made your fireplace is, time takes its toll. Over the years, temperature fluctuations in the chimney and extreme temperatures in the hearth gradually erode even mortar joints and masonry fireboxes.

All you can do here is make periodic inspections to look for gaps in your masonry fireplace and renew the refractory mortar. If things haven’t gone too far, fireplace repair won’t be too challenging.

Annual maintenance is usually adequate to detect a problem in time!

Tip #1

Using water

Water is often used when cleaning fireplaces. But the fact is that stone, brick and fireproof mortar are porous. Water penetrates deep inside and then begins to evaporate from the high temperatures. Steam exposure from inside the stones can lead to fireplace cracks or even complete loose bricks.

To get your fireplace shining clean again, there are other ways on how to clean soot off brick. Luckily, there are solutions on how to do it without the tedious scrubbing, and at the same time, update your home decor!

Construction mistakes

Another likely cause of a cracked firebox could be inferior materials or builder errors. Then, most likely, the masonry cracks will not be in the fireplace hearth, but in the chimney or near the damper.

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Also a possible cause of damage could be an overly heavy or overly protruding mantelpiece. How far a mantel can stick out can be found in Fireplace Mantel Heights article. An improperly secured TV bracket over the mantelpiece can cause the liner to crack.

Well, if this is indeed the case, then the smartest thing to do is to call for a professional chimney repair service. You can also look for a chimney sweep if this is available in your area.

Crack in refractory panels
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Why Repair Fireplace Crack Fast

It’s clear that a cracked fireplace refractory is fraught with grave consequences. But expensive repairs aren’t the most serious thing you can expect.

The main reason why cracked refractory should be repaired as soon as possible is the fire hazard. Let’s understand exactly how it works to safely protect your household and your family.

How fireplace refractory works

Of course, fireplaces are designed to withstand prolonged exposure of extreme temperatures. Well-constructed chimneys usually consist of two or more fire-resistant layers.

In prefabricated fireplaces, this is usually double-walled steel or steel with stone wool insulation. If it is a masonry fireplace, the most common is a double layer of brick laid on refractory mortar.

When fire burns, the fireproof coating around the hearth and in the chimney resists heat, sparks and burning embers. This is how refractory protects your walls and interior combustible materials from ignition.

Superficial minor cracks are not worth your concern, but if you see a fissure deepening or widening, it requires your immediate attention. Through the crack in refractory materials, sparks and burning embers can enter adjacent combustible materials. Needless to say, this is a huge fire hazard!

How dangerous my fireplace crack is

I’m going to assume that you most likely have a question – how do I tell the difference between a dangerous crack and a harmless one? And here is the answer for you!

The bad news is that even microcracks need to be looked after:

Take before and after photos at every fireplace maintenance to make sure cracks don’t spread or enlarge!

Tip #2

The good news is that there are specific recommendations from the National Chimney Sweep Guild on when to replace the protective coating. So, here’s what’s essential to know!

cracks in the brick firebox
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When firebox repair is urgent

Chimney Safety Institute of America recommends the following:

If the crack reaches 1/16 inch in width, this refractory should be replaced immediately!

Tip #3

You can easily check your crack with a nickel coin. If the nickel fits in your fissure, then it’s time for you to call for professional chimney repair service. By the way, they have a ‘Find Pros Near You‘ option on their website.

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More over, if you have owned your fireplace for a long time, check one more criteria:

If the surface of the fire-resistant layers is abraded over 1/4 inch wide, the refractory also needs urgent replacement!

Tip #4

But it’s always better to avoid going too far and make an upkeep panels or masonry repair. Here are some DIY tips for repairing your fireplace.

Repairing Firebox Cracks
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Repairing Firebox Cracks

For convenience, let’s talk separately about modern fireboxes and classic hearths. Whatever your fireplace is, don’t hesitate to restore it, or it could end up in a complete rebuild.

Sealing a crack in masonry fireplaces

The first place to start is purchasing fireproofing materials. This should be fire-resistant bricks and refractory caulk. This is the only way to stop flames penetrating to combustible materials.

Assess the existing damage in your firebox. If it is a cracked brick, seal the gap with mortar. If the cracks are large or loose bricks are found, it is worth replacing the damaged brick with a new one.

Go over the old mortar joints with a chisel or other handy tool, knocking out the loose mortar. Professionals call this process tuckpointing.

Try to find bricks that match the original masonry in size and color. Then, after the fresh mortar dries, you will only have to lightly sand the replaced brick to make the repair completely invisible.

Lastly, since you’re in the process of repairing your fireplace anyhow, go over the rest of the masonry and chimney joints to caulk even micro defects. Chimney cracking can lead to carbon monoxide leaks into your home. If the damage is caught early, masonry repairs will be simple and quick.

Pay attention to chimney condition. Gas leaks can be dangerous to your health!

Tip #5

Repairing a crack in refractory panels

Lucky owners of a new fireplace have a simple repair for a cracked panel. In case of damage, all you need to do is simply disassemble your prefabricated firebox and replace the needed part.

Steel fireplaces are designed to withstand extreme temperatures, but cracking can still occur from excessive heat. It is likely that the manufacturer of your firebox will be able to help you or offer replacement parts.

Either way it doesn’t look too difficult for your DIY project. All you have to do is remove the screws, replace the damaged refractory panel and put everything back as it was.

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A prefabricated fireplace usually has a metal chimney connected to the firebox by fasteners. The screws provided are sufficient, so you do not need mortar to repair it.

If you have decorative masonry around the hearth or on top of the steel chimney pipe, maintain it in the same manner as described for brick fireplaces. Although of course you don’t have to worry about it cracking as in traditional fireplaces.

Consult professionals

When in any doubt, contact the professionals. It is worth having an annual inspection to avoid dangerous damage to the hearth or a blocked chimney. With the the chimney service inspection report, your fireplace will operate safely. If you do decide to repair cracks in your fireplace on your own, here’s a video by @OldSoulMillennial to help:

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FAQs about Cracks in Your Firebox

Can I use my fireplace if its cracked?

The answer depends on how big the cracks in your fireplace are. If the gaps are as thick as a hair, you have some time to spare and the firebox can still be used. However, if you see the cracking increasing, do not hesitate to repair the masonry or replace the panels (depending on what type of hearth you have). If you can fit a nickel coin in the gap, your hearth is not safe to use and urgent repairs are required.

How serious are cracks in the chimney?

The chimney is the pipe through which gases pass after combustion, including carbon monoxide. A cracked chimney can allow harmful gases to enter living rooms. In large quantities and in an unventilated room, this can cause human poisoning. If you feel a gas or heat leak through the chimney, try to find it and seal it. Your health is at stake!

Crack in Firebox: Everything You Need to Know

Let’s summarize what we know about cracked fireplaces. Even minor cracks require attention, as fire is not the element that forgives mistakes. Try to seal all vulnerable areas of the hearth and chimney as soon as you discover them.

Hope, this article has answered all your questions about cracking your chimney or fireplace! Look for more helpful information, including pellet stove insert installation, in our Interior Design Tips section.

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