When you are looking for the best rocks to put in your gas fire pit, the easy answer is lava rocks. Sure, you can use colored glass instead, but we always prefer lava rocks. Where can you find lava rocks for fire pit and what should you look for when buying them? We will go over these questions and give you some tips for how much you should buy when you choose your lava rocks for fire pit.
What Are Lava Rocks Made From?
Lava rocks are made from, you guessed it, lava. When magma comes out of a volcano and hardens into a rock, the gasses dissolved in the rock evaporate leaving bubbles. Lava rock is porous and extremely heat resistant so it makes a great fit for gas fireplaces and fire pits.
How To Identify Good Lava Rocks From Bad Ones?
First, when considering which lava rocks to buy for your fire pit, you want to be sure you are buying the real thing. Lava rocks should be dark gray to black, and if you look closely you should see little air pockets in the stone. You also should make sure the lava rocks you are buying are intended to go into fire pits. The majority of lava rocks are gray to black though you will also find some lava rocks which are cream colored or red in color.
Three Shapes Of Lava Rocks For Fire Pit
There are different shapes of lava rock to choose from as well. There is the irregular lava rock, which looks like this picture.
And the tumbled / rounded lava rock like this picture.
The rounded / tumbled lava rock will always cost more, but in our opinion it has a great effect. It almost looks like Mexican beach pebbles when used in a fire pit and can really make the project pop.
How To Choose The Size Of Lava Rocks For Fire Pit
Next there’s the size to consider when picking lava rocks for fire pit. Lava rock is sold much like aggregates. It’s sold by the sieve or screen size. You’ll want to figure out how deep you’ll want your lava rock to be before you choose your lava rock size.
- When you only have a few inches to fill, you’ll want to buy the 1” or smaller size lava rock.
- If you have six inches or so to fill, you might buy the 1-3 inch size.
- Whereas if you are filling over six inches, you can use the 3-5 inch size.
Keep in mind, the larger the aggregate size you choose for the lava rock, the more air gaps you will have and the deeper you need your lava rock to be if you don’t want to see the pan of the fire pit or the fire ring itself. This is why we usually suggest going to a smaller size lava rock.
Best Lava Rocks For Fire Pit
How To Calculate Volume Of Lava Rocks To Fill Fire Pit
Make sure you buy enough to fill your fire pit up as much as you can without it looking like a mound of rocks. You will want to calculate the volume you need to fill in your fire pit. To do so let’s do some basic math.
Rectangular Fire Pit Volume
If you have a rectangular fire pit, measure the interior length, width, and depth of the area you plan to fill in feet. For example, if your fire pit is 3 feet x 2 feet x 6 inches deep you will multiply the following:
Length x width x depth = cubic feet of fire rock.
3 ‘ x 2’ x 0.5’ = 3 cubic feet of fire rock is needed
Circular Fire Pit Volume
If you have a circular fire pit the math is a little more complicated. First, measure the diameter of the fire pit interior and the depth you plan to fill. For example if the inside of your fire pit is a 4 foot diameter and your fill depth is 8 inches your math would look like this:
Diameter / 2 = Radius
4’ / 2 = 2’
Radius x Radius x 3.14 = Area
2’ x 2’ x 3.14 = 12.56 square feet
Area x depth = cubic feet of fire rock
12.56 square feet x 0.66’ = 8.29 cubic feet of fire rock needed
Once you have the cubic feet of fire rock, you need to look and find out the units being used to sell the fire rock. Often it’s in cubic feet, but sometimes it’s in pounds.
If buying lava rock for fire pit by the cubic foot, simply use the math above, and buy slightly more than you’ll need. It’s usually a good idea to buy at least 10% more to account for irregularities in shape. If the rock you are buying is in pounds, lava rock is typically between 35 and 40 pounds per cubic foot.
Therefore, if you have a 8.29 cubic foot fire pit to fill, you’ll need between 290 and 332 pounds of lava rock to fill up the fire pit. In this situation, I would order 365 pounds of lava rock just to be sure. Check to see if there’s not an additional shipping charge for breaking up the order. If not, you may want to buy 290 pounds and see how it looks. It just might be enough.
Lava Rocks For Fire Pit Summary
Now you should have all of the details necessary to get your lava rocks. Lava rocks are a great choice for your fire pit. Make sure to use our guide to find the correct volume that your fire pit requires. The 5 lava rocks that we recommended are our absolute favorites. However, there are many lava rocks available. As long as they have good reviews and fit your style, it’s hard to go wrong. Enjoy your fire pit and lava rocks.