Saturday, April 21, 2007
Building a Simple Block Fire Pit
Update 6/15/2011: after three or four years, this is the most popular article on this blog by far. You people really like your block fire pits! As you read below, put special emphasis on sighting. Where I built ours is too far away from the house for regular use and it sits disused most times. Something to think about when picking a spot.
Update 9/12/2013: I've written a follow up and have included some tips for cooking with a fire pit and making your own charcoal.
Generally, a good fire pit contains the burning items (hopefully some nice dry wood) but still radiates a pleasant amount of heat and light. A great fire pit can support a coking grate over hot coals or open flame. On a camping trip I took with friends in '05, I did all the cooking and everything except the eggs was cooked over an open flame. (I used a portable butane stove top for the eggs... too much close contact for the cook to use a camp fire). An effective fire pit will draw air from the sides into a sheltered interior. This keeps the fire from blowing out and allows it to draw oxygen so combustion can occur. If your fire pit is deep enough (from rim to embers) this inlet of air also helps the smoke go straight up instead of into your eyes, nose, and clothes. An finally, a really nice fire pit looks good. It doesn't stand out as the place you burn stuff in the yard. Ideally, it adds to rather than detracts from your landscaping.
So, tall order. We want a good or great, effective, really nice looking fire pit. To meet all of these criteria, I chose to make use of some of the extra landscape blocks I had from another project I intentionally over estimated materials on so I could do this project. (The customer didn't mind - it was me!) You can really use any non-flamable material. Steel, iron, rock, brick, even earth if you have a high enough clay content. I chose block for its consistency of shape and dimension. Flag stone, which is flat and can be selected for uniformity of height, would also make a good choice.
Start by selecting a location. If you cool your home ambiently (leave the windows open in the summer as opposed to running the AC) don't place it too close to your house or up wind if you can help it. A flat and level area is preferable as you will want to have stable footing for chairs and small tables around your fire pit. Also, you don't want to place it directly under an over hanging tree. While this seems very cozy, the heat from the fire can wilt, scorch and even kill your tree.
To prepare the site, outline the area you would like to transform into a fire pit with string, biodegradable marking paint, or my favorite, a garden hose. You'll want to excavate the sod and or weeds (depending on your lawn maintenance schedule) and an inch or two of top soil. If you are building your fire pit on top of an existing foundation, such as a concrete patio, skip this step. Be warned though that the heat from your fire could potentially age your concrete prematurely through uneven heating and cooling. Which brings to mind the method by which you will extinguish fires in your new pit. In the case of stone, concrete or any masonry, let the fire burn down when at all possible. Pouring cold water on a hot fire, more specifically, on hot stone or brick work, will lead to rapid temperature changes in the material which will most likely crack. The exception would be ceramic. If you use earth to make your fire pit and then fire the clay used for about two days at 1800 degrees Fahrenheit, you will have a monolithic mass that can withstand quite a bit of abuse. But since you aren't likely to do that, build small fires in your pit, not bonfires, and keep sand in a bucket handy if you really need to put it out quick.
The way I outlined my area to dig was to lay a coursing of block right on the ground in a circle the size I wanted my pit to be. The ground was a little soft from a recent rain, so dancing around on them for a few minutes (jumping up and down, hard) left some nice impressions and the perfect digging guide. I used the dirt to fill in some dog holes. Dogs live in holes? No, but they sure act like they want to when they find one occupied by a rabbit.
After that, I laid in some crushed #6 gravel. Do you need crushed #6 gravel? No. Sand will do. Pea-gravel will do. #4 crushed gravel will do. You want something that will compact to a level building surface. Replace all of the dirt you removed with your leveling granules of choice. Organic matter is not a good choice.
Then I threw up three concentric courses of block. The first two levels were of larger circumference than the top two to leave gaps for ventilation between the blocks. The top level was the only one that I set with the blocks all flush to one another.
Once the block was all in place, I filled the first coursing with more gravel (because I had some left over) and the second coursing with fist size rocks, the look I wanted in the bottom of my fire pit when people happened to look in. The rocks are easy to refresh later if I decide the current set has become too blackened with use.
As an optional final step, you can lay a patio or skirt of smooth gravel around the fire pit. It's nice to have the grass not growing right up to the edge of the pit, and adding a patio (not covered in this article) really raises the bar for back yard entertaining. In my case, we have a fire pit located remotely from the house and I used smooth gravel on top of weed barrier (plastic) as a 2' (two foot) skirt around the fire pit. Makes for a nice weed free place to set down a cooler, firewood, or whatever else you don't want wet from late evening dew on the grass.
Here's the materials list for my specific implementation.
36 4" x 11 " tapered landscape blocks (Old Castle "Old Forge" blocks)
10 cubic feet of crushed gravel (purchased by the ton for a larger project the week before)
20 cubic feet of smooth gravel (bartered from my neighbor with 20 cu ft of crushed gravel)
30 fist size round quarry rocks (purchased by the ton for general landscaping purposes)
If you buy the materials in the quantities specified, you will probably spend more money. Still, you should be able to do this for under $150.
A software architect by profession and maker of things by passion, Mr. Carter makes his home with his family in the Ohio wilderness. He readily shares knowledge and experiences and has interests in helping his fellow humans with basic finances and simple financial planning as well as spreading the joy of creating physical goods with practical aims. Mr. Carter can be hired for sundry needs on a sporadic, short-term basis. Email firstname.lastname@example.org to begin a conversation about your next project.