Why Use Fire Pit Lava Rock?

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By J. Herwick

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Choosing the suitable fire pit media (lava rock, fire glass, etc.) these days is something you don't necessarily get wrong. 

With so many solid options available in the fire pit market, it just comes down to your personal preferences.  

In this post, I will explore what makes fire pit lava rock the high-performing media that's the immediate “go-to” option for thousands of backyard enthusiasts and contractors/installers.

Functionally, fire pit lava rock provides a semipermeable barrier that protects fire pit burner components from the elements, facilitates the even distribution of flame and the resulting heat, and shields the gas burner from direct exposure to the surface flame. 

In addition to the above, fire pit lava rock is an extremely cost-effective option due not only to the fact that it lasts but that it really doesn't cost that much to use and replace as needed.

As we move on, I'll get into it a little more on how fire pit lava rock's unique makeup complements the fire pit's burner, its heat-resistant properties, how to determine how much you need and why, and how you can use it in combination with fire glass if you are looking to add a little color.

Why Lava Rock in a Fire Pit?

Modern gas fire pits are designed to use some type of medium, i.e. lava rock, fireglass, firerock, etc. to aid in even heat distribution and the protection of critical gas fire pit components such as the burner, burner pan, etc.  Fire pit lava rock is well suited to this job for a number of reasons.

What Makes Lava Fire Pit Rocks Unique?

Lava rock, or basalt as it is commonly referred to, has natural heat insulation and retention properties which provide the bulk of the benefits in gas fire pit use.

In addition to being good at handling the heat, lava rock can at the same be both water-resistant and aid in drainage providing “weatherproofing” for fire pits and their critical components.

Fun Fact:  In industry, basalt is melted down and spun into fibers used in home insulation products.  In addition to being an efficient insulator, this fiber is fireproof, a major plus for obvious reasons.

Primary Benefits of Using Lava Rock

Let's cover a few of the main benefits of using lava rock in a gas fire pit.

Fire Pit Burner Protection from the Elements. 

As mentioned above, a solid 3-4″ in. layer of lava rock in a fire pit can act as a shield for your fire pit's burner during a variety of weather conditions while helping water move to the fire pit's own drainage system

Burner Shielding from Surface Flame. 

When a gas fire pit is lit, the gas fuels the flame on the surface by moving through gaps in the fire pit rocks. 

At this point, the majority of the flame and heat are on the surface.

The natural insulating qualities of lava rock allow it to shield the burner from the intense heat up top,  making it last longer and perform better over time.

Gas Fire Pit Flame and Heat Distribution. 

One of the primary reasons lava rock is used in barbecue grills is because of its ability to evenly distribute and retain heat. 

If you've ever grilled before, hopefully, you haven't experienced “cold” spots on your grill where the heat distribution was uneven. 

Lava rocks for propane fire pit use serve the same purpose – provide a more even heat throughout the fire pit burner pan.

Secondary Benefits of Using Lava Rock

Lava Rock is Inexpensive. 

For what you get out of them, gas fire pit rocks are cheap, about $2-3/lb.

Lava Rock's Durable Natural Color/Look. 

Considering all of the qualities of lava rock I've mentioned so far, it's no surprise that it's so durable.  Not only will it do its job for a long time, but it should also keep its natural color with normal use.

Is Lava Rock Safe for Fire Pits?

I thought this might be a good time to include this mention.  Fire pit lava rock can rupture when heated if it is not totally dry and force hot pieces of rock from your fire pit. 

If you cover your fire pit regularly this shouldn't be an issue for you. If not, allow the wet lava rock in your fire pit to completely dry before your next burn.

How Much Lava Rock Do I Need For My Fire Pit?

For your gas fire pit to work the way it was designed you'll need to get the amount of lava rock you put in the burner tray right.  

Most gas fire pits need 2-4 inches of lava rock but your situation may be different.  Consult your user's manual for specifics.

Typically, you'll want to use a smaller size of lava rock as the first layer you put in the fire pit.  This will provide a base layer that just covers the burner, filling in gaps and giving both support and thermal protection. 

This smaller size lava rock layer fits together tighter providing a solid foundation for the next layer which can be comprised of larger fire pit rocks, fire glass, ornamental fire pit stones, etc.  

Pro Tip: Regularly check your fire pit's drain holes to ensure they are not blocked and water is able to flow freely.  Excess water pooling at the bottom of a gas fire pit's burner pan will keep the lava rock base layer from drying. A gas fire pit cover can help keep water out as well. – BT

Although the fire pit rock in this layer is smaller, the jagged, porous nature of lava rock is conducive to good drainage.  

Calculating How Much Lava Rock You Need

As a basic planning factor, expect each cubic foot of fire pit lava rock to weigh about 25 lbs.  Vendors will typically sell fire pit lava rock by the cubic foot or in certain pound increments. 

Where to Buy Fire Lava Rock

You can pick up lava rocks for fire pit use at your local outdoor store, or big-box hardware store (Home Depot, Lowe's, etc.), or order online.  Colorwise, red and black lava rocks are the most common options available.  

Make sure you've done your fire pit measurements and plugged them into a fire pit lava rock calculator, like this one from American Fireglass, when you are ready to pick some up or order for home delivery.  

By the way, use the Backyard Toasty promo code: AFG-S04KH, to get 30% off your fireglass order at American Fireglass.

In Closing:  Using Fire Pit Lava Rock

So, to close out, fire pit lava rock is a simple, durable, and cheap alternative to other types of gas fire pit media.  

It's going to protect your propane or natural gas fire pit's key components from unnecessary wear and tear from heat damage and the elements all while helping to keep the heat you want evenly distributed.

Check out my article Do Propane Fire Pits Smell Bad? more on what you can do to keep your gas fire pit in peak working condition.

Thanks for reading!  – BT

Can you mix lava rock and fire glass in a fire pit? 

A common question from those shopping for gas fire pit media is whether you can use fire glass over lava rock or even mix them together in the burner pan.  

The answer to both options is yes.

It's not uncommon to use fire pit lava rock as the foundation layer in the base of the burner pan, filled to a height slightly above the burner element. 

A thin layer of fire glass is then placed on top for a more decorative look. In addition to looking a little nicer for some, it's definitely a more cost-effective way to go.

Check out my article Can You Mix Lava Rock and Fire Glass in a Fire Pit? for more on lava rock in propane fire pits and using it with fire glass.

What is tumbled lava rock for fire pits?

Tumbled lava rock is a type of fire pit lava stone that's processed to remove the media's jagged edges, giving them a more uniform rounded shape. 

They are a good alternative to river stones, which can rupture under certain conditions.

If you want to mix lava rock and fire glass together that's doable as well and will lower your cost much like the layering option above.  How much of each in the mixture will be reliant on your own tastes.