Man Made DIY


02618

Aug 06, 2013

How to: Make a DIY Modern Concrete Fire Pit from Scratch

created at: 08/05/2013

There's no doubt about the cheer. Beside your fire you live in a private, glowing little world. All around you, fire shapes dance across rocks and bushes and tree trunks...Most of the time, you just sit and gaze at the caverns that form and crumble and then form again and gaze into the caverns that form and crumble and then form again between the incandescent logs. You build fantastic worlds among those pulsating walls and arches and colonnades. You sit, in other words, and dream. The East African has an almost limitless capacity for this masterly and delightful form of inactivity, and when his friends see him squatting there, lost, they understand and say in Swahili, poetically, Anahota moto - "He is dreaming the fire."    

Colin Fletcher, "The Complete Walker IV" (Knopf, NY:  p. 288)

   

I don't think there's much more to say than that. So, let's build our own DIY fire pit, yes? This version is cast of affordable, weather-resistant concrete that creates a sleek, modern look. It's portable but sturdy, and uses gel fuel, making it possible to have a quick 30-minute post grill session fire. It take a bit of care and proper prep, but this could be made in just a few hours for well under $50 in materials.

created at: 08/01/2013

Tools and Materials: 

  • Concrete mix
  • One extra-large bowl for exterior mold (ours was 17" diameter)
  • One large bowl for interior mold (ours was 15" diameter)
  • Non-stick cooking spray, or vegetable oil and paint brush
  • Large bucket for mixing
  • Medium-duty masonry trowel
  • Proper safety gear for working with concrete:
  • Heavy objects such as exercise weights (or you can use the rocks below)
  • Sandpaper or sanding pad in coarse and fine grits
  • Gel fireplace fuel canisters 
  • Replacement grill grate (ours was 14 1/2" diameter)
  • Fire safe decorative stones 

 

Casting the Bowl

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Creating this project is all about two components: finding the right materials and working safely. For the main fire bowl, we used the largest mixing bowls we could find. Check your local restaurant or party supply store for extra-large options. I opted for a plastic punch bowl for the outside because I liked the profile shape, and a stainless steel mixing bowl for the inside.

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Working with concrete isn't difficult, but it does require some finesse. First, it's fairly heavy and can be difficult to mix in large batches by hand. Secondly, it's extra important to use the proper safety gear to prep and execute your project. Work outside or in a well-ventilated area, and cover your work surface with plastic. I covered my bench in a plastic drop cloth, and taped everything down with ScotchBlue™ tape. 

 

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Also, be sure to wear proper safety gear to protect your eyes, skin, and respiratory system. For this, I consulted with 3MDIY.com for their suggestions of the best products from their 3M Tekk Protection line. I went with an N95 valved dust mask for sanding and grinding, and long sleeves and refinishing gloves to protect my arms and hands. For my eyes, I opted for these Walter White-style safety goggles, which not only protect from debris but also dust and irritants. Plus, I prefer them when wearing a respirator or dust mask, since they seal tightly and don't fog up.

 

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1. Once you're all prepped, spray your molds with non-stick spray. This will help release the concrete once it's dry. A thin, even layer over the inside of the outer mold/outside of the inner mold will do. 

 

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2. Then, mix up your concrete. It's hard to determine how much you'll need, but it's better to mix up more as you start than to rush to create more in the middle. I used about 1/3 of a bag for this project, adding water a little at a time until the mix formed a thick, cookie batter-like consistency. Make sure you're wearing your safety gear here; this is the time when most of the particulates and irritants are flying around. 

 

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3. Then, use the trowel to add the concrete mix to the outer mold. Fill it about half full, then check the inner mold to see how high the concrete comes up to the side. It's okay to take the inner mold in and out a few times, just make sure you don't lose all your non-stick spray. (You can wipe it clean and reapply). A friend or extra pair of hands is helpful here. Then, use weights or rocks to keep it in place. Some things to watch out for:

  • As you place the inner mold, make sure that it's centered so your bowl will have an even thickness all the way around
  • Keep the lips of the bowls coplanar for an even, symmetrical finished product
  • Adjust the weights so that you have the biggest inner bowl as possible while keeping the structure thick enough to be strong. You'll want to be sure that there's enough space on the inside to place your gel canisters beneath the lip of the bowl.

 

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4. For a super smooth finished surface, try this tip (I picked this up years ago from an episode of This Old House, I think): use something with a motor to vibrate the bowl to remove any air bubbles inside the mold. Here, I'm using my reciprocating saw without a blade, but anything will work: a powered sander, an oscillating or rotary tool, even an immersion blender.

One it's settled and things are no longer moving, allow the concrete to cure according to the package directions. (48 hours-ish)

 

Finishing the Bowl

created at: 08/01/2013

5. When your concrete has cured, carefully remove it from the mold. I lightly tapped on mine with a rubber mallet, first removing the inner bowl, then freeing the outer. It's solid at this point, so don't be afraid, but do be careful since it's quite heavy.

 

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6. Use a coarse sanding pad (60-80 grit) to clean up the top lip, and give everything a nice rounded profile. Again, since you'll be generating a lot of fine particulate dust, wear your safety glasses, gloves, and dust mask.

 

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Wipe away the debris, then give the whole thing a round of fine grit (220) sandpaper. Since concrete doesn't have any fibers or grain like wood, you don't have to work your way up. Any sanding is just the removal of irregularities or smoothing things up. 

 

Assembling the Fire Pit

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7. Lastly, take it outside, and place the gel fuel canisters inside. I found mine at a local fireplace/swimming pool/outdoor recreation store, but you can find them in some hardware or home improvement stores or online.

 

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8. Place the grill grate in the bowl. The one I used was a 14.5" bottom grate (for the charcoal, not the cooking surface) for a Weber kettle grill. It rested perfectly about 1/2" from the surface of my 15" internal diameter bowl. If you can't find one, you can cut a larger one to size with a hacksaw or grinder, or create your own from hardware cloth or steel mesh.

9. Then, cover the grate with a layer of rocks. I'm using "Mexican beach pebbles" that I found at a garden center. These are commonly used with fire, so I can be sure they'll stand up to the heat and won't explode into flaming shrapnel with extended use. So, just be sure that whatever rocks you're using are appropriate for the purpose.

created at: 08/05/2013

Light It Up!

While the flames on these aren't bonfire-sized, the gel canisters put out quite a bit of heat, and all kinds of fun ambiance. At some point, I'd like to make a few of these and place them around my patio or deck. (At some point, I'd also like to have a patio or deck). But, for about $40 in materials (many of which I can reuse), I have a great, easy-to-use backyard fire solution, that requires nearly zero work to start or snuff out, and can keep our outdoor hangouts going well past sundown.

created at: 08/05/2013


Oh! And here's a Pinterest/social media friendly image. Would you please be so kind and help share the goodness?

created at: 08/06/2013

 

Enjoy!

This post is a collaboration with 3M DIY. To keep up-to-date on projects, products and sampling visit 3MDIY.com.

This post was sponsored by 3M DIY. All opinions are mine alone.

Post Comments

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How do you snuff it out? Sounds like a dumb question typing it out, but if I needed to snuff it while it was still burning pretty well? Do you put a giant lid over it, or do you have to move the hot rocks?
I would love to make this, but somehow build in handles for easier moving. Perhaps a circle of wire with wire loops somehow worked into the cement? Any suggestions?

@Kyle - Sure, I included these tips in the post above. 

  • As you place the inner mold, make sure that it's centered so your bowl will have an even thickness all the way around
  • Keep the lips of the bowls coplanar for an even, symmetrical finished product
  • Adjust the weights so that you have the biggest inner bowl as possible while keeping the structure thick enough to be strong. You'll want to be sure that there's enough space on the inside to place your gel canisters beneath the lip of the bowl.

This is a great and simple design! It seems difficult to get the concrete to set in a really symmetircal way so that is looks as good as it does in your photos. Do you have any tips to make sure that the bowl is even?

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Kellie, Trish -- Yes, you could use wood in the fire pit.  It wouldn't be as picturesque as the images. --

Anonymous -- You really need to lubricate the molds before use.  -- Getting a 'stuck' item out of the mold, well I have distroyed molds before when demolding, or pound it with a hammer enough and it will eventually come out, but either the mold or the item or both are pretty well messed up.

Trish -- Let it sit for 4 to 8 hours before demolding.  Yes it will 'cure' for a long time to come (years - concrete keeps getting harder over its life, but most hardening is done within 28 days).  To help it get stronger long term, keep it wet, but don't get carried away.  It will crack less if it is kept moist.

Also, this is cheap enough, if it doesn't work, chalk it up ot experience and make another!!

Can you burn wood in it?
Nice project

Is there a youtube video of this!?!

Really aesthetic. Must try it up here in chilly Sweden.

@Anon - Have you tried a rubber mallet? Vibrating them? Don't be too shy about force. If your concrete has cured, it's rather strong.

My molds are so so SOO stuck! (even after following instructions to put vegetable oil :() HELP!

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Thank you for such a brillant (no pun intended) idea. I do have a couple of questions though. First off, does the concrete need to be 'cured'?  Second, and last, is it safe to burn wood in?  Thank you for your time in answering my questions, I look forward to your reply. Looks like a project to do with my grandson.....he'll love it!

 

j'aurais voulu savoir comment vous pratiquiez pour eteindre le feu en fin de nuit 

merci de votre réponse

 

sabine

Help....I used cooking spray on the molds but they are stuck and can't seem to get them out...any ideas?

 

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This turned out awesome, a few things I would like to change, but not sure what I can do, other than go buy bigger bowls.  I went with a little smaller bowl, 13"OD x 12" ID, with a 10.5" grate.  13oz. real flame gel fuel cans stand 4" tall, this puts my grate just about even with the rim.  So I cut an 8" wide can down to 2.5", perfect!  Nope, the gel cans burn for about 3 hours in their own can, I poured one into my trimmed down can and it only lasted 30 min, I understand the product was spread out, and knew that it would burn quicker, but I was hoping for at least an hour, cause there is enough room in the can to pour 3-13oz gel fuel cans in, and figured a 10pm-1am burn would be good enough.  Not like you want to be lifting the grate and rocks out during a party and putting more gel fuel cans in, I was trying to get the longest burn possible.  I did use the dye to make my concrete a dark gray, just make sure you are measuring how much concrete and dye you use, my second one turned out much lighter than the first.

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Nicely done, I love this!

Do you have any idea how I can use my 4ft.x4ft. heavy metal fire bowl.

I had this made for myself last year and now I have to figure out how to light it , and with what, and I would like to use the colored glass?? Any ideas?

Can you put real wood in it to burn?

Can this concrete bowl be used for burning wood? I really like the look, but don't like buring the chemicals. Thanks!

Tha nks it is gone be my next week end project, very nicely done.

so awesome, Love it I will give it a go one day. :)

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