It looks like its on its way to being a fire pit, right? Well the cats seem to have a different idea. I assume you can tell what is pictured on the left. They obviously think I like them SOOOOO much that I would buy 600 pounds of concrete and mortar, 1000 pounds river rocks, work mortar until my fingers and hands were cracked and dry, and brave some of the hottest recorded days in Houston to build them a stone litter box. I bet they are bragging to the strays and gloating to the chickens about it right now.
Regardless, I finally have a fire pit. I decided I wanted one about 2.5 years ago, and I’ve been overthinking it ever since (refractory clay? foundation? rebar? will the rocks crack? how big? vents?). Since I am never going to be more jobless than I am now, I went ahead and pulled the trigger.
I decided to use regular mortar rather than fire clay because mortar is free relative to fire clay. If it doesn’t stand up to the heat, I will just patch it back together. I did decide to build a foundation, but I did not use rebar. The foundation is a ring and is about 5″ deep (though it looks much shallower in the picture to the right). It took 240 pounds of cement just for that. Do you think the cats are already plotting?
After letting the concrete set for a day, I began piling on the rocks and mortar. I am not sure I got the consistency exactly right, but it seems to be holding. I was using a trowel religiously until I discovered that I am not gifted with a trowel. I started using my bare hands after the first layer. BAD IDEA! I thought my hands were getting pruney due to the wetness of the concrete. Instead, there was some kind of chemical reaction. My skin started cracking after about a day. I did some research, and the pH level of cement is 12-13 whereas human skin is 5.5. Then I read the label. God Bless Texas, because it said that I could have gotten cancer if I was in California.
Here is the finished product, although some of the mortar is still drying. The pit itself has an ID of about 4 ft. and a height of a couple feet. I included some vent holes by mortaring in 1″ PVC pipe and pulling it out after the mortar set. In addition to ventilation, I may use one of the holes to plumb black pipe if I decide to build a propane burner for easily starting fires and/or cooking.
I want the fire to be above ground level, so I have also built a grate. This was intended to serve two purposes. It raises the fire above ground level and lets air get to the embers. I was about to finish by welding legs and a truss for support, but I started getting nervous that the grate might not be a great idea. My concerns relate to the fire getting too much air, burning through wood too fast, not having the insulation of the ground, and losing that campfire feel. Rather than welding on legs, I am going to place it on blocks for a test run. It will become a cooking surface if I don’t like how it acts.
I’d like to close by offering my advise and ridicule if you ever want to build something like this. Notice I did not offer my help. It was much, much more of a pain than I ever imagined.