Introduction: $50 Fire Pit Using Concrete Tree Rings
We recently moved from the remote north woods of Wisconsin where people create great lakeside campfires by digging large fire pits into the ground and lining them with large rocks. We now live in a residential neighborhood in the Central Valley of California. Here, campfires are confined to pre-built pits or structures. People build only small controlled fires to minimize the risk of sparks blowing into neighboring combustibles when the fire is left unattended. These smaller campfires are also easy to extinguish, with less risk of embers continuing to burn.
Even with these restrictions, our family still loves to sit outside around an evening fire in the backyard. But we didn’t want to spend a small fortune on a pre-manufactured patio fire pit or a contractor built unit. We were also not sure where we might permanently want the pit located. So we needed something we could take down and move to a different spot without a lot of trouble or expense.
Fortunately, while cruising the aisles of Home Depot recently, we saw concrete tree rings (circles that are used for flower beds at the base of a tree) on sale for $2 a section. We borrowed a tape measure and quickly determined that the rings might make a dandy low cost fire pit that would incorporate a small Weber grill (which we already owned) as an inner firepot, allowing a very controlled burn and positive air shut-off to extinguish the fire when we were ready to call it a night.
- Weber Smokey Joe Portable charcoal grill or equivalent 14" diameter grill to be an insert in the rings ($30 new)
- 4 sections of 14" inside diameter concrete tree ring ($2 to $3 each = $8-$12 total) -6 sections of 24" inside diameter concrete tree ring ($2 to $3 each = $12-$18 total)
- 2 cubic feet of small stones, pebbles, road gravel or decorative rock ($0-$20 depending on how fancy)
Total cost: $50-$80 depending on your taste in stones.
Step 1: Constructing the Inner Ring.
Find a nice level area of your yard or create a level circle approximately 3 feet in diameter. It's not absolutely necessary but we sprayed our pit area with weed and grass killer to make a bare spot. You will notice the ring of browned grass surrounding the pit in the final photos. This is due to the weed killer and not the result of heat from the fire. We also placed a layer of weed barrier cloth under the pit to prevent grass/weed from growing up into the pit. The tree rings will be more stable on bare earth than on grass, particularly if you have Bermuda grass like we do. Also, you should have no problem if you want to place your pit on top of a concrete or brick patio.
The trick to turning tree rings into a decent looking fire pit is to make the ring two sections tall by turning the fluted top sections upside down so they interlock with the fluted bottom sections. The first photo shows what the 14" tree ring sections look like when you buy them from the store and the second photo shows them stacked. They don’t fit perfectly but the small air gaps look sort of decorative in my estimation and are barely noticeable once the unit is being used.
Step 2: Adding an Outer Ring
We thought the 14" tree rings looked a little puny by themselves, so to give the fire pit more mass we surrounded the inner ring of 14" tree ring sections with an outer ring of 24" diameter sections. The sections are 2" thick, so the outer diameter of the completed fire pit will be 28".
Note that the 24" outer rings have a very convenient tab type locking design. One end of each section has a tab and the other end has a slot. This helps a great deal to stabilize the rings when they are stacked two high.
Step 3: Filling the Void
You will quickly notice that when the 14" rings are stacked inside the 24" rings that there is a 3" gap between the inner and outer rings. You will also notice that each 14" ring is about an inch shorter than each 24" ring. To solve both of these problems the outer ring is erected first and then filled approximately 2" deep with small stones. The inner ring is then set on top of those stones. You’ll have to do a bit of trial and error to insure the tops of the inner and outer rings will be level when they are completed. Once the inner and outer rings are in place, fill the 3" void between the rings with more stone.
Step 4: Installing the Weber
The Weber Smokey Joe grill may come with legs attached. If so, unscrew the 3 connecting screws and set aside the legs. In an amazingly beneficial coincidence, the Weber grill is perfectly sized to slip right into the inner circle of the pit and just enough lip remains above the surface of the pit for the cover to fit tightly in place. Once the Weber is in place and you start a fire, it would be difficult and perhaps hazardous to adjust the lower air vent of the grill. So set the vent opening however you want before you put the grill in place. I set ours about half open and it works great for creating nice small fires. And when the cover is put on and the top vent closed, the fire will go out in very short order. If you want or need more or less bottom air for your fire, you can easily remove the grill to adjust it between fires when the unit is cool.
Step 5: Light It Up
Get out the graham crackers, marshmallows and Hershey bars. It’s time to enjoy your fire pit.
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I have a 36" fire ring and I'm thinking of using these tree rings with rocks to fill between. so how many tree rings do I need to fit the 36" ring and the outside? I have some unused so not sure how many more I would need.
I don't think that will work using the tree rings pictured in the Instructable. These rings have a fixed radius and thus can only make a circle of one size. The smaller rings make a circle with a 14" diameter and the larger rings make a circle with a 24" diameter. If you try to put them around a 36" circle (or larger) they will not create a nice circle. Rather it will be a ring with a very wavy circumference. I suppose they could be set up that way but I would question the stability of that sort of ring.
I'm not totally certain I understand your question. Are you intending to build an inner circle of tree rings inside your existing 36" fire pit ring? If so, you would need 6 sections of the 24" I.D. ring sections...that's assuming you are going two high.
No first circle would be around the fire ring which is 36" diameter, then second circle with the rocks in between.