Instructables

40 Inch (Inner) Diameter Retaining Wall Fire Pit ~ $110

Picture of 40 Inch (Inner) Diameter Retaining Wall Fire Pit ~ $110
As stated in the title this fire pit cost me about $110 for the raw materials. The inner diameter is 40 in (102 cm) while the outer is 54 in (137 cm). I purchased materials from both Home Depot and Lowes and I recommend visiting both because they had different block colors and sizing if you want to create a variation of this pit.

Raw Materials: 6 bags of .5 cu ft of drainage gravel (Lowes)
                           42 Retaining Wall Blocks (Home Depot)
Tools Needed:
                            Rubber Mallet
                            Level
                            Shovel
                            Angle Grinder with concrete-ready blade (only needed if you get blocks that do not have two level faces)
 
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Step 1: Place 14 Blocks in Circle

Picture of Place 14 Blocks in Circle
You could use a string and two pencils to mark out a more perfect circle, but I found it easiest to just lay the blocks in the best circle I could. Then, use a shovel or a stick to mark the outer and inner edges of the blocks.

I would also like to note at this point that you could use any number of blocks for different size fire pits and 12 would actually be the easiest to set up because the angles work the best. I chose 14 simply because I liked that size.

Step 2: Remove Blocks, Dig, and Lay Gravel

Picture of Remove Blocks, Dig, and Lay Gravel
Dig out in between the two circles you marked to a depth of  2- 3 inches. Fill this with gravel. It will help when you need to level the blocks and it also helps with drainage.

Dig a hole in the center of the pit about 20 in deep and 15 inches in diameter. Fill this with gravel for drainage.

Note: My pit was located in an area with wood chips so the area already drained well, hence less drainage rocks were needed. If you have clay soil I would advise following the instructions from this old house on the trench/ hole depths. Or you can use your own discretion.
Have u had any blocks crack?
jcastaneda52 months ago

Should i use type S mortar to make the joints better and a little more secure. it will also add some height to the blocks so that way i could maybe save some more money by not having to buy more block. i work at Lowe's so i can already get some stuff cheap, but i swear... i must have had a Jewish ancestor somewhere along my family tree because i am just such a penny pincher. i already asked they guy in commercial and he said he would have to look it up so i sent him the link to this ible, we'll see tomorrow.

AverageGuy (author)  jcastaneda51 month ago
As long as you do not build the pit too high then the weight of the blocks alone should be be fairly secure. This is especially true if you build a pit smaller than mine so that the blocks align in their natural angles. It could help tie things together though as you said. And it would probably look nicer since you could fill in the gaps. Just be prepared for a good deal more work. I myself would not recommend putting mortar in between the layers of blocks (to increase height) as it would be a ton of extra work and I personally think it would not look as nice. If you are that concerned about stability you can use construction adhesive to glue the blocks to those below them.

Hope this helped
valcider1 year ago
Very nicely done.I'm looking to build something similar in my own backyard.This gives me a good start.Thank you!