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This modern concrete fire pit can be built over a single weekend and is a great centerpiece for outdoor entertaining. This isn't a difficult project, but it's time consuming and labor intensive. Concrete fireplaces and fire pits should be constructed carefully. When exposed directly to high amounts of heat, the moisture trapped inside concrete can expand and cause the concrete to crack and in extreme situations, explode. I lined the inside of the fire pit with fire brick and filled the bottom with lava rock to ensure that the majority of the heat didn't come in direct contact with the concrete. I built this fire pit in southern California, so I didn’t have to worry about putting in footings that go below the frost line. If you're building a fire pit in a cold climate, I recommend putting a sonotube footing under each of the four corners.

Step 1: Supplies + Tools

Quikrete 5000 (20-25 Bags)
QUIKRETE® 5000 Concrete Mix is a commercial-grade blend of stone or gravel, sand, and cement and is specially designed for higher early strength. This is the recommended concrete mix to use because of the high early strength and low price. It’s great for making tables, pavers, stools, and lamps and is typically found in 80-pound bags at Home Depot, but 60-pound bags are also available.

Fire Bricks
I used fire bricks from a local masonry supply yard. They aren't the prettiest looking, but after a few fires they will turn black from the soot. Fire bricks are heat-resistant and will protect the concrete from cracking.

Mortars
I mixed my own mortar from a combination of Portland cement, mortar clay and sand. I followed the directions that came on the mortar clay bag.

Rebar
I bought pre-cut rebar in 12" and 36" sections. I should've purchased 18" long sections for the verticals. I recommend using a combination of pre-cut 3/8" diameter rebar. Use 18" long pieces for the verticals and 36" long pieces for the horizontal pieces. Make sure you drive the vertical pieces through the gravel and into the ground so that the ends are at least 3.5" below the top of the wood forms. Wire the horizontal pieces to the vertical pieces so that the horizontal pieces will be embedded in each layer of concrete. This rebar frame will keep the different layers of concrete securely bonded to each other.

Quikrete 3/4" Gravel
I used about 7 bags of Quikrete 3/4" gravel for the foundation layer.

Lava Rock
I used two 5 gallon buckets full of lava rock that I purchased from the masonry supply yard. The lava rock is heat-resistant and won't crack or shatter.

FOR THE FORMWORK:

2x4s + 2x6s
I used 2x4s and 2x6s held together with 2.5" deck screws to make the panels for the formwork.

L-Brackets
I used L-brackets to join the panels at the corners. I recommend 6" L-brackets.

RYOBI 18 Volt Cordless Drill

RYOBI 18 Volt Circular Saw

RYOBI 10" Sliding Compound Miter Saw with Laser

Step 2: Download the Concrete Fire Pit Plan

Click here to download the concrete fire pit plan.

Step 3: Cut the Wood

The outer frame will be made of 4 panels that are 43.5" long. Each panel is made from 2 pieces of 2x4 and 2 pieces of 2x6. I used a circular saw to cut them, but a compound miter saw would make this task a little easier. If you do use a circular saw, I recommend using a speed square to make sure your cuts are nice and straight. I used 6" L-brackets to join the panels at the corners.

Step 4: Assemble the Panels

I used 2.5" deck screws and 15" long pieces of 2x4 to make the 4 large panels for the outer frame.

Step 5: Make the Inner Frame

The inner frame is made from 2 panels that are 23" long and 2 panels that are 20" long. Make sure to put the L-brackets on the inside corners of the frame since the outside ones will be buried in concrete.

Step 6: Place the Frame + Mark the Hole

Place the frame in the desired location and mark about 6" around the outside perimeter.

Step 7: Start Digging

Since I built the fire pit in southern California, I didn’t have to worry about putting in footing below the frost line. If you're building in cold climate, I recommend putting in footings that go beneath the frost line under each corner. I dug about 8" down and used a stamper to flatten and compact the soil at the bottom of the hole.

Step 8: Spread Some Gravel

I spread about 3.5" of Quikrete 3/4" gravel in the bottom of the hole and raked it as level as possible before stamping it down.

Step 9: Place the Formwork

Place the frames into position and measure the distance between the inner frame and outer frame to make sure the inner frame is properly centered.

Step 10: Secure + Level the Formwork

Once the frames are in the right position, use some scrap 2x3s and deck screws to lock them into place. Then use a 6 foot level to make sure that the formwork was level. I used a rubber mallet to knock down the high corners to make it more level.

Step 11: Place the Rebar

I drove the rebar through the gravel and into the ground. I should've used longer rebar instead of the short 12" long vertical pieces. I wired 3' long pieces horizontally about 2" from the bottom of the hole.

Step 12: Pour the First Layer of Concrete

I started with a 3.5" deep pour of concrete that would serve as the foundation of the fire pit. I mixed the Quikrete 5000 in a wheelbarrow and shoveled it into place. Renting a mixer would have made this a lot easier, but I enjoyed the exercise. Let the concrete cure at least 20 hours before laying the brick.

Step 13: Lay the Brick

Once the concrete has cured at least 20 hours, get ready to lay the fire brick. I mixed the mortar per the instructions on the bag of mortar clay. I started with a thick base of mortar about 1/2" around the inner perimeter of the formwork and then placed the bricks one at a time. I spread mortar on the side of the bricks before placing them so that they would stick together.

Step 14: Pour More Concrete

Once the mortar sets, mix and pour another 5 inches of concrete. I could've poured it all at once, but mixing concrete by hand is exhausting and doing it this way allows you to remove any extra braces that could be in the way of screeding before doing a final pour. I also added in additional rebar since my 12" bars where already covered. I wanted to make sure that the layers of concrete where bonded together.

Step 15: Pour the Final Layer

After letting the previous layer of concrete cure about 20 hours, I poured the final layer of concrete. I used a hoe to push the concrete down into all the corners and a wooden dowel to vibrate the concrete by hand.

Step 16: Screed the Top

I used a flat piece of wood to screed the top of the concrete. Work the screed back and forth to level the concrete.

Step 17: Use a Float

I let the concrete set about 30 minutes and then used a metal float to work the cream to the surface. I spent about 10-15 minutes working the surface.

Step 18: Steel Trowel

After using the float, I waited about 1 hour and then used a steel trowel to finish the concrete. I did my best to get the surface as smooth and flat as possible. It isn't perfect, but it looks great!

Step 19: Cover + Keep Moist

I covered the concrete with some boards and a sheet to make sure that nothing touched the wet concrete. I used a garden hose to keep the concrete moist over a 48 hour period.

Step 20: Remove the Formwork

Removing the outer frame was easy. The inner frame required some cuts with a circular saw. I should've made some diagonal cuts in the interior panels beforehand, but not a big deal either way. After about 20 minsutes with a pry bar, hammer and circular saw, I got the wood out. I then sprayed off the concrete with a hose to clean it.

Step 21: Pour in Some Lava Rock

I poured 2 buckets of lava rocks into the inside of the pit. This creates a nice, well-drained surface for starting fires and covers the 3.5" foundation layer of concrete.

Step 22: Before You Light a Fire

I recommend letting the concrete cure at least 30 days before lighting a fire. I also recommend not letting a fire burn for longer than 2 hours for the first 3 months. It takes a long time for concrete to fully cure, and you don’t want the moisture to expand inside and cause cracking. Be responsible and don’t make super large fires. The concrete is protected by the fire brick and lava rock, but if you make giant bonfires and let them burn for hours on end, the concrete could crack.

Good luck making your own concrete fire pit and please email or tweet photos to @benuyeda or ben@homemade-modern.com. For more DIY ideas and projects, visit us at HomeMade Modern.
<p>Great idea - I'd like to reprint this in Wood-Fired Magazine. Please contact me at editor@woodfiredmag.com </p>
<p>How much did this cost? i'm thinking about making this same design but without firebricks! <br><br>my idea was to get the concrete that made for fireplaces and make a smaller center box after the first part harden and place it back in the middle and do like a 3 inch layer on the wall of the inner fireplace with it!<br><br>maybe even lay a layer across the top for added protection!!!</p>
<p>Very cool</p>
<p>I'm not an expert, and because the top is wide this may be moot, but i would think that some air channels, under your walls. would be good feeding mor air into the coals and fire from below will allow for a less smoky fire, and encourage a upward motion of the flame and heat. </p>
That would give more oxygen to the flame, burning hotter which could cause it to get TOO hot for the pit
<p>I'de be curious to see some follow up photos of how this is holding up after repeated use before going with this design. Looks great though thanks for the instructable! </p>
<p>funtastic</p>
<p>I do not see the purpose of driving the re-bar through everything and into the surrounding earth. The re-bar will begin to rust and expand and eventually break the concrete as it does so. I was taught to make sure all the re-bar was completely covered with concrete. Very pretty fire pit and if wide enough draft would not be a real problem . The way it is constructed a gas jet would be very easy include. yes fire brick!</p><p>uncle frogy</p>
<p>I agree with WellFedEd, great way to show an Instructable, and great project! When I saw the picture of your fire pit, I knew this would be a project for this coming summer. Excellent job!</p>
<p>I appreciate you making the high-speed video on the making of your fire pit, all Instructables would benifit with this!</p>
<p>I like your design.<br><br>I would make it differently, but I play with higher temperatures.<br><br>Maybe I could modify your design so that it can be used as a forge and to smelt metal :-D</p>
<p>Very nice, stucco the walls or stucco and pebbles/small rounded stones various colors to make it pretty.</p><p>Bad news this send smoke in all directions all the time, the same base with a nice enclosure (fireplace with chimney), yield little/no smoke in everyone's face, and no need to wash all your cloths every time you fire this baby up. The chimney allows you to put a nice fire grate at the top to stop embers. It also adds an enclosure you might use to cook food in. Provided you add a rack/elevated floor.</p><p>Still, very nice construction details. And do consider a decorative fascia, you did such a nice job it deserves a facci bella . </p><p>you can try ventilating from below with a simply rack. Or retrofit a vent line. Since you did not need a footing, dig straight down 3-4 feet away make a good 5 gallon sized hole. It needs to be below what would be the bottom of your rock layer dig another just as deep , but maybe as big as a 2 gallon bucket, just as deep, then use a brass nozzle on a hose to water blast under the unit you then go in the pit dig straight down. I did this many times to get wire where I wanted power. I also had a home brewed set up with lengths of black pipe that I could attach to a hose. I could do about 6 feet straight, which is good for going under a walkway flag. I loaned it out and it is gone :-( never to return.....</p>
<p>We've been looking for a plan for my son's Eagle project. He wants to build a fire pit for burning/retiring flags at our local soldier's retirement home. With the four nice sides like that we could inscribe a military service on each side.</p><p>Thanks for posting.</p><p>Suzanne in Orting, WA</p>
<p>Not to bad a design it could have done with some pipes on each side to provide some airflow to the pit kind of like a burning bin has holes all around the bottom. good effort though and it looks clean a precise. you could paint the outer walls with a coloured textured wall coating, just a thought. and for all the tree huggers that built one out of carbon neutral products I hope your pockets and uyour wallets are empty now.</p>
<p>You don't have to remove the interior wooden frame, because you could let it burn out with the first few fires.</p>
<p>nice job, looks like it is burning fine just the way it is. Add a steel grate on top, some ground beef. Cook first, hang out later all on the same fire.PS. Snidey70448 turn off your computer you're carbon foot print is getting too big.</p>
Nice design. Just needs some air flow.
<p>This is an awesome idea!!! looks very good. Have you used it a few times yet? Whats your plan to clean out the ashes? also, how good does it burn? You didn't integrated air intakes towards the bottom of the flame, wondering if this is something that should have been done or does it suck enough air down over the edges?</p><p>One more thing as a precaution... make sure to build a few small fires in the pit and gradually increase their size. the fire bricks and lava rocks are an excellent idea but you want to make sure to dry the cement slowly. There is likely still pockets where water can accumulate and potentially cause a steam explosion which could be very dangerous and destructive. </p>
<p>This is excellent, but I have a question; I remember hearing somewhere that when you use rebar, you should always completely encase it in the concrete so that it doesn't rust and eventually degrade. Is that inaccurate or would that even matter for this project?</p>
<p>Wow, it is a super project for next summer around here, thanks</p>
<p>Nice, but did you leave a vent for air to enter at the bottom? I would think this necessary to avoid smoking-out the neighbors...</p>
I like how it looks like a premade fire pit it makes it look modern
<p>instead cut the timber inside it can just be burned or cut all 4 panels same size to easy removal </p>
<p>Been looking for a way to make a small fire pit.. This is a GREAT idea, Thank you for sharing..</p>
<p>How many Bags of cement did you end up using?</p>
<p>What are your plans to clean out the ash once you have burned many many fires?</p><p>Also... any recommendations for adding a natural or propane gas line to this design for easier fire starting?</p><p>Looks great!.. I nee dto make this in my yeard over the next few months... </p>
<p>Your designs are always so nice! Thanks for sharing them with us.</p>
<p>this is amazing, such a sleek look. great work !</p>
<p>This looks great! I love how much time and thought you put into your preperations. It shows!</p>
<p>Looks great. I am glad you added the piece in the beginning about concrete exploding. I built a fire on a concrete slab once because the ground was wet and it indeed exploded. There was an air pocket in the slab that pressurized from the heat and with concrete's weakness in tension it eventually failed. Luckily no one was hurt. Great 'ible.</p>

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