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.

 

created at: 08/01/2013

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.

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So does the fire last as long as the gel fuel canisters last? For every use, you must remove and replace a cannister then? How long do they typically go for?

Maybe restaurant supply store has large bowls
Rather than drill a hole in the bottom, I would put dowels in the mix at the bottom allowing the concrete to set and you have the holes for draining. The dowels can also serve the purpose of preventing the two forms from being compressed too much causing a thin bottom. Just cut the dowels to the depth the bottom should be.

I would make a recommendation for the design if you plan on leaving it outside year-round... Drill a hole (after it has cured) in the center bottom. This way rain water, melted snow, whatever, will be able to drain out and not make this into a bird bath.

You lost me at "concrete mix."

where do I get the 15 and 17 inch bowls?

I plan on making this, I would love to make it much larger however, and am having trouble finding something I can use as a mold.  If you or anyone out there has any suggestions, please send your ideas to me.

Has anyone made this as a wood burning fire pit? What modifications, if any, are needed? Thanks

What a great weekend project,,, Fun and easy,,, will doing this for my daughters new apartment that has a jungle for a back yard,,, She is so excited to clean and design something fun to enjoy... Love it

Not for me unless you can modify it to be larger and burn wood. As it is, it is only a decoration and a waste of gas.

great idea i made it and its realy impressive.

Thanks

Picked mine up out of the mold and it broke to pieces :( left it for a day and a half does it need to stay out longer? A specific concrete?

@1berto images seem fine to me  - are you still not seeing them?

the images are brockem.. can you fix it???

Okay after reading this I ran to Home Depot and picked up concrete. Then the party store to pick up gel flame and plastic bowls. This gad to be the easiest project to make. Direction were exact. Next I plan to make larger and incorporate a propane rank for around pool. Thanks! Now I gave request from others to make.

I wonder if this would work with the tin can/toilet paper/70% alchahol diy burner can be used with this?

Can you make this for a gas / tile rock pit?

Very, very, very excellent!

For stuck molds: how about dumping ice water into inner mold to make it shrink?
Saw a large concrete bowl today at homedepot..was called a planter..34 dollars....also read that hand sanitizer 80% alcohol burns well and is cheaper
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