Can fire pit rocks explode? - MAX Fire Pits (2024)

Can fire pit rocks explode? - MAX Fire Pits (1)

Max Firepits

  • Published:April 1, 2024
  • infire pit, fire pit rocks, fire safety

Do fire pit rocks explode? It's an important question that you need to consider before firing up your camp fire. in this article, we explore the different types of rocks and see which ones to use and which ones to avoid.

Can fire pit rocks explode?

Table of Contents

I would say that every week here at MAX Fire Pits, we get about 20 emails and phone calls asking the same question; “Can fire pit rocks explode?”

As we all know, outdoor fire pits offer a unique blend of warmth and ambience, inviting us to gather for stories, laughter, and marshmallow roasting. However, there lurks a potential danger many of us overlook: the danger of exploding rocks. Yikes!

After all, spending a night around open fires is meant to be relaxing, and the last thing you want to watch out for is danger when you sit around.

Key Takeaways

  • Granite and lava rocks are safe for use in fire pits.
  • Porous or wet rocks can trap water and cause explosions when heated.
  • Always use dry, non-porous rocks to ensure fire pit safety.

Why do rocks even explode?

At the heart of this problem is water — specifically, water trapped within the pores and cavities of particular rock and stones. When heated, this water expands rapidly, exerting pressure from within. This can cause rocks, particularly porous varieties, to shatter violently in a camp fire, sending fine, sharp pieces of rock shrapnel flying​ into the air.

Sedimentary rocks like limestone and sandstone, along with some volcanic and metamorphic types, are most likely to explode due to their structure, which can easily trap moisture, quickly turning to steam and pressure. Any smooth rock sourced from a river can become dangerous when it gets hot in a firepit or open fire.

What rocks to avoid?

To mitigate this risk, it’s crucial to know which rocks to avoid. Porous rocks, including limestone, sandstone, pumice, and shale, are notorious for absorbing water and should be avoided in your campfire.

Here’s a quick list of which rocks to avoid:

– River rocks

– Wet rocks

– Basalt

– Stones from a river bed

– Sandstone

– Concrete

– Pumice

River rocks, often rounded from years of water erosion, are remarkably deceptive. Despite their smooth appearance, they may harbour significant moisture and are thus highly explosive when heated in a fire pit or campfire.

River rock is also usually pretty easy to obtain, so it seems like a quick and easy solution. However, it has a high tendency to explode, so we suggest you avoid it at all costs.

Can fire pit rocks explode? - MAX Fire Pits (2)

Choosing Safely: Rocks That Won’t Turn Your Fire Pit into a Hazard

In contrast, denser, non-porous rocks like granite, marble, and slate offer a safer choice. Their compact structure makes them less likely to absorb water, reducing the risk of explosions. Manufacture options like lava rocks and fire glass provide a reliable and attractive alternative for those seeking added peace of mind.

Lava rock and stone, formed from cooled molten lava, naturally withstand high heat. However, they can still pose a risk if they become wet. Similarly, fire glass is designed to endure extreme heat without exploding, adding a modern touch to your fire pit with its reflective beauty.​

Rocks that are less likely to explode with heat:

  • Granite
  • Lava rock or stone
  • Marble
  • Slate

Remember, if in doubt, always talk to a professional who is qualified to give advice on what rock to use.

Prevention is the most important.

Preventing rock explosions starts with selection and maintenance.

Dry your rocks thoroughly before use, and consider ‘curing’ new lava rocks by applying heat slowly to release any trapped moisture safely. This process involves placing the stones in your fire pit, lighting it and allowing it to burn for up to 45 minutes under supervision. Watch for any sign of steam or cracking or if the rock starts to break.

Regular checks for moisture and avoiding using rocks recently submerged in water can further reduce any issues.

Bringing It All Together

An outdoor campfire can be the heart of your garden, a place for relaxation and socialisation. Understanding the risks associated with certain types of rocks and taking steps to reduce these dangers can ensure your fire pit remains a safe, enjoyable feature of your outdoor space.

Remember, the key to fire pit safety lies in choosing the suitable materials and carefully maintaining your setup. This way, you can enjoy the warmth and charm of your fire pit without worry.

Disclaimer:We are not qualified to advise you on what rocks to choose. This article is a rough guide based on sources gathered from the internet. We are not responsible for rocks that may explode. Please consult a qualified professional before deciding which rocks to use in your campfire.


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What rocks should you not use in a fire pit? ›

What rocks to avoid? To mitigate this risk, it's crucial to know which rocks to avoid. Porous rocks, including limestone, sandstone, pumice, and shale, are notorious for absorbing water and should be avoided in your campfire. River rocks, often rounded from years of water erosion, are remarkably deceptive.

What can cause a fire pit to explode? ›

Concrete blocks, pea gravel, river rocks and other materials that are often used in DIY fire pits can trap water inside. When they are heated up, this can cause an explosion. Here's a demonstration of what can happen when the building materials hold a little too much water and pressure builds up inside.

Will lava rock explode in a fire pit? ›

Special Note: Even lava rock can explode when heated due to moisture getting trapped inside. Make sure to use caution the first time you use your fire pit after rain or when you first install it.

Are stone fire pits safe? ›

With an outdoor fireplace, there will be fewer concerns about the heat getting too high or too low or even a fire accident that would directly affect the house. Outdoor fire pits with stones are the safest.

Are all rocks fire safe? ›

Not all rocks are suitable for use in a fire pit, so make sure you check the type of stone before using it. Porous or wet stone, such as sandstone or river rocks, may crack or explode when they reach high temperatures. Hard rocks like granite, marble or slate are suitable for use in fire pits.

What is the best rock to put in a fire pit? ›

We typically use ¾” clean crushed limestone for the gravel fire pit patios we build. We recommend crushed limestone around fire pits because of its excellent drainage. Plus, it compacts well, giving a solid base for seating and other heavy items.

Can bricks explode in a fire pit? ›

The wrong bricks can explode, and the wrong mortar can cause the fire pit to crumble and fall apart. This is why it is imperative to use kiln-fired bricks and fireplace mortar.

Why do fire pits pop? ›

How Moisture Causes Fires to Pop and Crackle. In addition to low combustion efficiency, trapped moisture can cause fires to pop and crackle. Even if a piece of firewood looks dry, it probably has moisture inside its pores. After all, trees absorb water to grow and survive.

Why are my fire pit stones cracking? ›

While many stones are very resistant to heat, the most important thing to be aware of is that they're not 100% heat-proof, and under the right conditions, stone can crack in extreme heat. This occurs when natural stone is exposed to very high heat in a short period of time.

Are rocks or glass better for fire pits? ›

The glass pieces are non-toxic and will not leave behind any ash or soot, which is great for keeping the outdoor area clean. Lava rocks, on the other hand, are known for being very porous and light. Due to the porous texture, they contain no moisture – and do not hold any heat in.

Why put lava rock in bottom of fire pit? ›

Notably, lava rocks have a very porous texture, which implies that: They contain no moisture. They don't hold any heat in, allowing the flames to heat you. They allow more airflow to your burner.

How long do fire pit rocks last? ›

Lava rocks are low maintenance and last for 3+ years depending on how often you use your fire pit. However, regularly moving lava rock around can shorten its life span as it may cause it break into smaller pieces.

What rocks should not be used in a fire pit? ›

Crushed Limestone

It is often used as the primary material for the fire pit patio itself, creating a sturdy and functional surface. However, it's important to note that crushed limestone should not be used inside the fire pit itself, as it can be an explosion hazard.

How high should a stone fire pit be? ›

A good rule of thumb is to make an above-ground fire pit 12-14 inches tall. This is a few inches shorter than standard patio furniture seat height. If you want to be able to sit on the edge of the pit itself go a bit higher, 18-20 inches will be comfortable.

Should I cover my stone fire pit? ›

A cover not only extends the longevity of your fire pit but also saves you time and money. The weather can take a toll on your fire pit in many ways, from water and sun damage to your fire pit filling with debris.

Why not to use river rocks for fire pit? ›

Crucially, don't ever use river rocks. There are several reasons why you should never use river rocks for a campfire, with one of the most obvious being that they are often more porous and can contain water. When this water gets hot it creates steam and the rapid expansion can cause the rock to explode.

What rocks hold heat in fire pits? ›

Soapstone Hot Rocks are the best alternative to Lava Stone and Glass. They're designed to be used in every type of gas fireplace, grill, fire pit, and BBQ.


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