Build the Walls
Both small stones and bricks work well for this type of fire pit. The difference is primarily aesthetic, so choose whichever you like better. Roberts does note that using smaller stones makes curving the wall easier. You’ll need about 1.5 cubic yards of stone for a 2-foot-high pit. But make sure you buy a little extra so you’re not stuck making another trip to the store.
When you’re ready to lay the stones, mix Type S mortar with water. You can test if your mortar is mixed properly by smearing some on the side of a stone or brick. If the mixture sticks, you’re ready to go. If it runs down the side, it’s too wet and you need to add more mortar. If it clumps and falls off, it’s too dry and needs more water. You’ll want to mix about one-quarter of a bag at a time so it doesn’t dry out.
Start at the bottom and work your way up. Place the first stone at the edge of the hole, then put ½ to 1 inch of mortar on the side of the stone and place the second stone so that it touches the first. Continue until you have a full circle. For the next layer of stones, do the same, but put mortar on the bottoms of the stones as well as the sides, so that each stone is attached to the others. Roberts says the key to laying stones is to offset the layers so the seams of your stones do not line up. Continue stacking until your wall is 12 to 18 inches high if you intend to use it solely for warmth and atmosphere. But if you want your fire pit to double as an outdoor grill, your wall should be 2 feet tall for optimal cooking conditions.