Are There Cracks In Your Firebox? Here's Why And What You Should Do.

Your fireplace and chimney are designed to withstand years of extreme temperatures and weather conditions. However, nothing lasts forever, and no matter how well-built your fireplace is, eventually, time takes its toll.

The firebox is where the fire burns, and because it undergoes a constant heating/cooling cycle and extreme temperatures, it’s prone to wearing out more quickly than other parts of the system.

Fluesbrothers Chimney & Fireplace examines the causes of firebox damage and what you can do to repair it.

firebox cracks damage, Mission Hills KSCauses of Firebox Cracks & Damage

Builders use firebricks and refractory mortar to construct modern fireboxes because these materials withstand extreme temperatures better than standard bricks or stone.

Despite the durability of these materials, they’re still prone to damage.

The leading causes of firebox damage include:


Brick, stone, and mortar are porous and absorb water like a sponge, so even a tiny amount of water can get in, causing the material to swell and eventually crack.

Wear & Tear

Although firebricks and refractory mortar resist heat, the constant exposure to high temperatures takes their toll, causing these materials to wear out over time.

Also, weather and foundation movement can cause your chimney to tilt or lean, putting stress on the entire system leading to cracks in the mortar joints and loose bricks.

Faulty Construction

The quality of a chimney and fireplace depends not only on the materials used but also on the builders. If the contractors that built your fireplace lacked skills or used inferior materials, the fireplace will wear out more quickly than it should.

The problem with firebox damage is that it happens slowly, and many people don’t notice the damage until it’s too late, and rebuilding is the only option. The best way to protect yourself from expensive repairs is to hire a professional chimney repair service for annual inspection and maintenance to fix minor problems before they get out of hand.

How Serious is Firebox Damage?

A well-constructed fireplace and chimney have fire-resistant layers and a flue liner to protect the combustible materials around the firebox and behind the fireplace from catching fire.

Ignoring firebox damage puts your home and family at risk of fire and carbon monoxide poisoning.

Also, if the cracks are large enough, burning embers can come through and contact the wall behind it.

Another concern over cracks in the firebox is the chance that gases and carbon monoxide can leak out into your home.

Besides the risk to your home, there’s a financial risk resulting from ignoring firebox repair. You can repair most cracks if caught early by sealing or chiseling away the damaged areas and repointing.

However, if you wait too long, you run the risk of needing a complete rebuild of your firebox, which is time-consuming and expensive.

The Fluesbrothers are masonry fireplace experts. Our masonry repair includes firebox rebuilding and repointing, mortar crown repair, and damper repair.

What About Prefabricated Fireboxes?

Many builders prefer manufactured fireplaces in new home construction because they’re more cost-effective than masonry fireplaces.

Like their masonry counterparts, manufactured fireplaces use refractory materials to reduce heat transfer from the firebox to the combustible materials around it.

However, like masonry fireboxes, prefab fireplaces and their refractory panels are also prone to cracking caused by excessive heat.

Hairline cracks are expected, and you can still use your fireplace safely; however, this is a problem you want to keep your eye on if it worsens because of the risk of fire.

According to the Chimney Safety Institute of America, you should replace a cracked fireplace refractory panel if the crack is 1/16 of an inch wide or if you can fit a nickel into the space.

The bottom line is that while you can safely operate your fireplace with minor cracks in the firebox, you must call a professional chimney repair service as soon as you notice damage to protect your family and home.

Repairing Firebox Cracks

It’s understandable to want to save money on home repairs, but professionals should perform some fixes, and that includes firebox repair.

Depending on the damage, a professional chimney repair contractor may fill in the gaps with refractory caulk to seal them.

Some repairs require tuckpointing or replacing loose bricks, which technicians with the training and experience should handle to do these repairs accurately.

Also, professionals are certified and insured, which means you get peace of mind knowing the repairs are safe and will last.

About Fluesbrothers Chimney & Fireplace

We’re a full-service chimney service company serving residents throughout the Kansas City metro area for over a decade.

chimney repairs, Prairie Village KS

We’re members of the National Chimney Sweep Guild and are fully certified by the Chimney Safety Institute of America and the National Fireplace Institute.

Here’s what you can expect when you hire us.

  • Over a decade’s worth of experience
  • Fully certified, licensed, and insured technicians
  • 100% satisfaction guarantee
  • Full-service chimney cleaning, inspection, and repairs
  • Dryer vent inspection and cleaning
  • Accurate diagnostics
  • Free estimates
  • Financing options

Whether you need firebox repair, chimney sweeping, inspection, or fireplace repair, you can count on Fluesbrothers Chimney & Fireplace Services in the Kansas City metro area. Please book your appointment now by calling 913-236-7141 or via our online form.