How to Decide What to Use in the Bottom of Your Fire Pit

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Last Updated on August 3, 2021
Jim Bob

Jim Bob

A long-time contributor to Seriously Smoked. Jim has had a lifelong relationship with the art of grilling, passed on from his father and grandfather to him.

what to use in the bottom of a fire pit

Lining the bottom of your fire pit is an important step in ensuring the longevity and safety of your wood burning fire pit. The problem is deciding what exactly to use. There are plenty of materials that work, but not all of them are great for every kind of fire pit.

However, all of these materials do share a few things in common, as do all the materials you shouldn’t use. For that reason, I think it’s important to give a bit of context for WHY many materials are good or bad for lining a fire pit rather than simply listing off materials.

Read More: Look at our review of trendy propane fire pits being sold this year.

1. What to Look for in a Liner?

backyard

The most important thing, of course, is something that’s not flammable. This sounds like an obvious step, but I think it bears saying. Whatever you line your fire pit with shouldn’t be combustible at any temperature you’re likely to reach.

As important though is that the material be cheap and readily available. This will make it very easy to replace whenever you need to scoop it out (as over time, things left over from the materials used for your fire are going to leave flammable bits left in the bottom).

Alternately, use a material that doesn’t need to be replaced at all, or very infrequently. Like very dense rocks.

2. What Not to Use?

fire at night

In the planning phase of your fire pit design, it’s advisable not to use rocks. At least, don’t use common rocks you can find around most places. Many rocks are porous or just not able to stand up to high heats. In the best case, these rocks will crack and need to be replaced often. In the worst case, they’ll explode, sending flying shrapnel everywhere and potentially hurting or even killing someone.

It’s important that you don’t use rocks or bricks with air pockets inside when building a fire pit from scratch for a similar reason, as it’s incredibly unsafe.

Small rocks can sometimes be safe (no bigger than a fingernail), but it’s better to always be cautious with the things your using in your fire pit.

3. Common Easy Materials to Use

fire

Sand

Sand is a quick and easy option if you live in a more desert-like area, or near a beach.

Sand is non-combustible and doesn’t turn into glass except at very high temperatures and/or under pressure, so you’re good there. It’s readily available and can be found easily in bulk. Even if you don’t live somewhere it can be “harvested” easily, you can buy sand in bulk relatively cheaply.

Sand also helps distribute heat evenly, helping to maintain integrity in a metal fire bowl, and aid in cooking as well if you’re using your fire pit for that.

On the flipside, sand has a few drawbacks. If you’re using a metal fire pit (rather than a brick one), when it gets wet it can speed up corrosion, potentially destroying your fire pit quickly. It also has a tendency to mix with ash and create a slush that needs to be cleared out, so it needs to be replaced often.

Dirt

Much like sand, common soil is available pretty much anywhere, for free.

In many ways though it’s inferior to sand. It’s less good at distributing heat, and has all the same drawbacks as sand (the added corrosion speed and need to be replaced).

Pretty much everything that applies to sand, applies here. Just for a different part of the world.

Make sure your dirt is free of roots and grass and such though, before you use it. That can make it a little more difficult to get a hold of.

Gravel

In many places gravel is also available for free, and is potentially the best of these materials in terms of longevity. Gravel doesn’t get wet, and won’t speed up corrosion. It also won’t need to be replaced often, if at all.

Of course it doesn’t conduct heat nearly as well as sand, so keep that in mind.

4. Specialized Materials

bonfire camping

There are many home improvement ideas you can use when installing a fire pit, and one of them involves thinking of the right decorative media to use.  To be aesthetically pleasing, cozy outdoor fire pits would use materials like rocks as decoration. Such materials are also needed for lining the bottom of the fire pit.

Lava Rocks

These are probably the best material by a wide margin. Their heat retention is by far the best of all the materials on this list, and it makes cooking using your fire pit an absolute breeze.

These rocks are very fire resistant and don’t retain air pockets, so they won’t explode. Even better, they look very nice; they’re a common choice for a reason.

So, the confluence of stylish and useful can’t be beat, especially since they effectively never need to be repaired. The only real downside is they can be kind of expensive.

Fire Pit Glass

Much like the lava rocks, these are made specifically to line the bottom of fire pits.

If you want your pit to have a little more sparkle, these are your best option. They also come in a wide variety of colors, so can be color coded to match the coloration of your fire pit for a bit of extra style. Just be careful that you won’t be using the products that are hazardous to burn.

Of course, you trade style for substance here. Glass doesn’t conduct heat very well, so they’re worse for cooking. And fire pit glass can be pretty expensive. It will also need to be cleaned or replaced after a while if you’re using it in a wood fire pit rather than a gas one, to get all the soot off so they keep shining in the light.

I still recommend them for style purposes, but mostly for gas fire pits, unlike all these other options (which are suitable for any fire pit, but mostly wood fire pits).