5 Materials to Put in the Bottom of Your Fire Pit

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A fire pit often serves as the heart of your outdoor living space, where marshmallows get toasted and stories are shared.

Want to make your fire pit even more awesome?

Sand, gravel, lava rock, or fire glass are popular base layers for protecting and embellishing fire features. Each option has a unique look that can match any vibe.

Plus, installing them won’t take too much of your time.

Today, I’ll guide you through the best materials to put in the bottom of your fire pit. 

1 – Dirt

Let’s kick things off with a material that’s pretty much everywhere and won’t cost you a dime: dirt.

Dirt is convenient and readily accessible, offering some degree of heat resistance.

However, using dirt isn’t without drawbacks. It might contain organic debris that can burn in the fire pit.

Make sure to cover your fire pit when it’s raining. Dirt and water equal mud, and cleaning up that mess is no fun!

If your fire pit has cutouts at the bottom, dirt is a terrible idea, as it can clog the hole and hinder airflow.

While dirt is low-cost, it looks plain and unattractive. If you’re looking for aesthetic appeal, explore other alternatives from this list.

Pros of Dirt

Check out the pluses of dirt as a base layer for your fire pit:

• Free and accessible
• Heat-resistant
• Safe to use

Cons of Dirt

The following downsides might make you think twice about using dirt:

• Messy when wet
• Not visually appealing

2 – Sand

Sand is an abundant supply along beaches and riverbanks. It’s widely available and cheap, and you can use nearly all kinds, including play sand.

Lining the bottom of your fire pit with sand helps distribute heat evenly.

What’s more, sand is an excellent insulator. It’s a great choice for metal fire pits, as it helps preserve the bottom of the pan.

Without sand, hot spots can form on your fire pit, which are areas of concentrated heat. Over time, they can cause the metal to warp or deteriorate.

In other words, sand can prolong your fire pit’s lifespan. Additionally, sand is fire-resistant and prevents red-hot cinders from scattering.

That said, not everyone is a fan. Some argue that adding sand can impede airflow, especially for fire pits with air holes or vents.

Another consideration is that sand retains moisture, causing metal fire pits to rust. Waterlogged sand also weighs a ton, so it’s an issue with portable fire pits.

And let’s not even get started on the cleanup.

I recommend periodic moisture checks and replacing sand as soon as you find it’s damp. Read my post to find out if it’s okay for a fire pit to get rained on.

Types of Fire Pit Sand

Fire pit sands vary in particle size and composition. Check out the different options you can find at your local hardware store:

1 – Silica Sand

Derived from crushed quartz, silica sand is refined, heat-retaining, and comes in various colors. It ensures effective heat distribution and is an attractive option as a base layer for a fire pit.

Because of the high amounts of silicon, the particles don’t crumble in extreme heat.

The best thing about silica sand is that you can’t scorch it. While it’s true that silica melts into glass, it’s impossible to do that in a backyard fire pit.

2 – All-Purpose Sand

All-purpose sand is finely crushed rock and minerals. The particles are finer than gravel but coarser than silt.

The sand is screened, washed, and dried, removing all moisture. It settles well but becomes uneven with time.

3 – Paver Sand

Paver sand is a coarse builder’s sand containing pulverized rock, limestone, and granite. The rugged particles interlock, forming a sturdy base for your fire pit.

Sometimes called C-33 or leveling sand, it compacts smoothly over time.

Pros of Sand

Here’s why sand is a popular material as a base layer for fire pits:

• Promotes uniform heating throughout the fire pit
• Provides a stable base for kindling and small wood
• Is affordable and easy to clean
• Prevents embers from scattering outside the fire pit

Read my post about more reasons to put sand in the bottom of your fire pit.

Cons of Sand

Below are the downsides of using sand:

• Depending on your fire pit design, sand could obstruct crucial airflow.
• Using the wrong type of sand can pose safety risks.
• Too much sand can lead to higher flames and uneven burning.
• Separating ashes from sand can be challenging.

3 – Gravel

Another popular choice for the base of a fire pit is small stones or pea gravel. While gravel has a higher price tag than sand, it offers similar benefits but with a cleaner aesthetic.

The primary difference is in their heat absorption capacity. Gravel isn’t stable at extremely high temperatures.

You can opt for larger stones found in your yard or purchase bags of landscaping stones from your local home improvement store.

For a DIY fire pit base, cover 10% of the pit with an even layer of gravel.

Pros of Gravel

Here are the advantages of using gravel:

• Affordable
• Widely available
• Clean-looking
• Low-maintenance

Cons of Gravel

The negatives of using gravel include:

• Limited heat resistance
• Low insulation

4 – Magma Lava Rocks

If there’s something we all learned from high school Earth science, it’s that molten magma solidifies into lava rock when cooled.

The most common type is basalt, which is dark, fine-grained, and spongy.

Since lava rock comes from volcanic activity, you can expect it to weather the hottest temperatures without cracking or exploding.

It retains heat for extended periods and drains water rather well.

Tumbled stone is another variant. It undergoes a process that smoothes its rough surface, resulting in a pebble-like finish.

This transformation gives it a more modern aesthetic. The downside? 

These stones are typically too large on their own. Small-sized lava rocks are the perfect filler to cover the burner and ensure even heat distribution throughout the pan.

You might want to read my guide on how to clean lava rocks in your fire pit.

Pros of Lava Rock

You’ll love lava rock on your fire pit for the following reasons:

• Permeable and weather-resistant
• Highly durable
• Resistant to high heat 
• Inexpensive
• Colors don’t fade over time

Cons of Lava Rock

• Limited color options
• May add significant weight to a portable fire pit

5 – Fire Glass

Fire glass is simply colored tempered glass. To achieve its stunning hues, it’s infused with metal oxides while in a molten state.

For instance, copper oxide makes rubies, while cobalt oxide produces blues.

Fire glass can transform any drab fire feature into a mesmerizing spectacle. It boasts an extensive palette of jewel tones, from rich blacks to fiery reds.

The glass chunks conceal the burning gas jets and reflect the flames, giving it the illusion of dancing fire atop a bed of gems.

Fire glass is inert, meaning it remains unchanged by fire. It doesn’t contain combustibles, finishes, or additives that can react with the flame.

Additionally, it can withstand searing heat without burning, discoloring, or compromising safety. And you won’t need a spark screen or heat shield when using it.

Types of Fire Glass

You can pick a fire glass from these finishes:

• Reflective Fire Glass: Offers a mirror-like finish
• Semi-Reflective Fire Glass: Has a partially reflective finish
• Non-Reflective Fire Glass: Shows more of its true color when the fire pit is lit

Popular Styles of Fire Glass

Fire glass comes in various styles, each adding a unique flair to your fire feature:

• Crushed Fire Glass: Gravel-like pieces of fire glass
• Fire Glass Diamonds: Larger, rounded glass pieces with a diamond look and a smooth surface
• Fire Beads: Smaller, coin-shaped fire glass
• Fire Glass Cubes: Ice cube-shaped fire glass

Pros of Fire Glass

Check out the benefits of using fire glass:

• Available in different sizes, shapes, colors, and finishes
• Durable and long-lasting
• Low-maintenance
• Safe to handle
• Customizable to match any design scheme

Cons of Fire Glass

Consider these drawbacks before checking out your cart:

• Pricey
• Limited heat retention
• May shatter when wet and heated

What to Put in the Bottom of a Wood-Burning Fire Pit

Stone foundations are a solid choice for wood-burning fire pits as they help control the flames. In-ground fire pits are safest on a paved surface, or you can assemble one on a layer of gravel and sand.

Sand is also an ideal liner for portable steel fire pits. It soaks up heat and distributes it uniformly.

You won’t worry about hot spots that can weaken metal over time.

Moreover, sand creates a buffer between the fire and the surface underneath, whether it’s your patio or non-grassy ground.

Alternatively, you can use a fire mat to prevent falling embers from catching on anything.

Dense stones like bricks or patio pavers are also fantastic base materials for fire pits. They have a high heat tolerance, so you can safely enjoy your fire pit.

What Not to Put in the Bottom of a Fire Pit

You’d think stones are the most fireproof of materials. Well, believe it or not, exploding rocks are pretty commonplace.

Steer clear of porous or damp ones, such as limestone, sandstone, or river rocks.

Why?

These stones can trap water inside. When heated, the trapped moisture can turn into steam and ignite.

Always check your owner’s manual for the manufacturer’s recommendations when choosing a base layer for your fire pit.

And for the ideal scenario, ensure all your fire pit materials are bone-dry. If possible, cover your pit after every use.

Why Is Bottom Material Important for a Fire Pit?

The proper material helps with heat insulation, drainage, and fire pit durability. Think of it as the foundation for a blazing good time!

So, you’ve got a roaring fire going. Without a good base layer, the heat can wreak havoc on the bottom of your fire pit.

The proper materials act like a buffer, protecting your patio or grass from getting roasted. (See my article about whether having a fire pit on grass is safe.) 

And let’s not forget the horror of your fire pit turning into a mini-pool after a rain shower. Disastrous, right?

So, bottom line—pun intended—choosing the right material isn’t just about aesthetics. It ensures that your fire pit lasts through all those chilly nights, year after year.

Fire Pit Safety Tips

Here are some handy tips for keeping things safe when you’re hanging out by the fire pit:

• Skip the accelerants like gasoline or lighter fluid—better safe than sorry!
• Find a safe spot for your fire pit, away from potential hazards.
• Avoid placing the fire pit directly on grass, as it can dry out and catch fire.
• To protect your patio or deck, consider using a fire pit pad or mat to shield surfaces from heat and sparks.
• Keep your kids and fur babies at a safe distance from the flames.
• Don’t wander off and leave the burning fire unattended.
• Once the ashes cool down, scoop them out. Discover some fantastic ways to put that fire pit ash to good use in this post!
• Trash and paper aren’t fire pit materials—steer clear!
• Keep a fire extinguisher or hose nearby to address unexpected flare-ups.
• Consider investing in fire safety gear.

Frequently Asked Questions

What Is the Best Base for a Fire Pit?

You’ve got plenty of choices, but at the end of the day, it all comes down to what fits your budget.

Plain sand gets the job done, but if you have cash to spare, consider topping it with lava rocks or fire glass.

What Kind of Sand Is Best for Fire Pits?

Silica sand is the go-to choice. It settles evenly and holds up exceptionally well under intense heat.

Silica sand naturally comes in shades of white and tan, but you can grab it in different colors to match your fire pit.

How Much Sand Do I Need for My Fire Pit?

Usually, you’ll want about 1–2 inches of sand at the base. A 5-pound bag of sand should be sufficient for a small fire pit.

Of course, different sand or fire pit brands might throw in their two cents, but that’s the ballpark.

The key is to spread it evenly, keeping that thickness consistent. When in doubt, a bit more sand won’t hurt.

Can I Use Regular Glass for a Fire Pit?

No, tossing regular glass in your fire pit is a disaster waiting to happen.

When exposed to intense heat, regular glass can crack, shatter, or even explode. Some have chemical additives like lead oxide, which emits super-toxic fumes when burned.

Meanwhile, laminated glass contains plastic that can turn black and melt in high heat.

If you want to add color and sparkle, stick with fire glass.

Does Fire Glass Burn?

While it might look like it does, fire glass doesn’t burn at all. It maintains its integrity without melting, breaking, or discoloring under furnace-like conditions.

However, ensure that the glass pieces are free from moisture. Lighting the fire pit with wet fire glass can lead to uneven heating, causing the glass to shatter explosively.

Why Is My Fire Glass Turning Black?

If you notice black soot on your fire glass, adjust your burner settings accordingly. It indicates the incomplete combustion of gas.

Can I Use Fire Glass for a Wood-Burning Fire Pit?

Fire glass is compatible with any propane or natural gas fire pit, but it’s a no-go for traditional wood-burning fire pits.

Can You Mix Lava Rock and Fire Glass?

Absolutely!

Fire glass doesn’t come cheap. To slash the quantity by half, consider using small-sized lava rocks as a filler underneath the fire glass. 

How Do You Prepare the Ground for a Fire Pit?

Clear the area around the fire pit from any debris, leaves, or other flammable materials to prevent accidental fires. Make sure the ground is level to keep the fire pit from tipping over. 

For in-ground fire pits, create a fire ring by digging a shallow, circular trench about 6–12 inches deep. This helps contain the fire and prevents it from spreading.

If you’re using a portable fire pit or building one with bricks or stones, place it on a non-flammable surface. This can be a layer of sand, gravel, or fire-rated bricks.

Can You Build a Fire Pit on Dirt?

Sure!

You can build a fire pit on dirt as long as the chosen location is clear of grass, vegetation, or debris.

Also, select a flat, level area away from overhanging foliage, structures, or anything that might catch fire.

Final Thoughts

There are various materials to put in the bottom of your fire pit. But guess what steals the show as the crowd favorite? Yep, you guessed it—good ol’ sand.

Sand evenly disperses heat but won’t burn a hole in your pocket.

If you’re looking for extra oomph, you can level up with lava rock or fire glass. These options bring sizzle to your outdoor hangout.

Because, honestly, nothing beats the cozy glow of flames and the joy of creating memories around a well-loved fire pit.

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