How To Build A Square Fire Pit With Cinder Blocks

The materials needed for this project are: 14′ cinder blocks, a straight edge and masonry bit, concrete mix and other necessary tools. In this simple process, the first step is to lay out your cinder blocks on level ground to form a perfect square. Then you will use your straight edge along its corners to make sure they meet at right angles as well as cut the bricks if necessary. Add 2 inches of concrete along three sides of the block base, using a trowel or different size cinder block as a screed board. Use an even depth throughout the entire process so that there won’t be any exposed bricks once you’re done. After about 20 minutes of waiting for it to dry, you can fill in all gaps between bricks with sand and mortar mixture.

A cinder block square fire pit is a great, inexpensive way to create a backyard gathering spot. It’s easy, safe and can be finished in just a few hours. Building your own fire pit also means more usable space than an above ground model.

Fire pits are a great way to spend a cool evening in the backyard. In this article, we’ll show you how to construct your own square fire pit using simple cinder blocks. We’ll provide step-by-step instructions for how to build each layer of the pit and finish it off with some decorative bricks or stones. This project is fairly straightforward; however, you may need to call a friend over to help you put on the top row of bricks or stones (unless, of course, you’re part giant.) Once complete, your fire pit will serve as an entertainment hub for years to come.

Step 1 – Stake out Your Fire Pit

  • Stake out your fire pit area using a rope to outline the perimeter of your future fire pit. Make sure that you secure the stake in the ground, so it doesn’t move when you’re digging below.
  • Measure with a tape measure how wide your fire pit will be by measuring on either side of where you placed your first stake and marking lines with chalk or writing some kind of measurement in dirt so that it’s visible before starting to dig.
  • Use a shovel to dig out enough space for a hole at least three feet deep (36 inches) and as wide as your measurements showed on either side of where you placed your first stake (no less than 30 inches).
  • Level off the surface inside by placing one edge of a level along one edge of the hole until both ends make contact with dirt underneath; this allows you to see if there are any bumps or dips before proceeding further into leveling work so that there aren’t any unwanted surprises later on down this road.

Step 2 – Prepare the Area

  • Clear the area of debris, including any rocks and stones that you don’t want in your fire pit.
  • Make sure that the ground is level. This can be done by digging out dirt on one side of the area and filling it back in with sand, gravel or crushed rock. If you go this route, make sure that whatever you use to fill in your new flat surface isn’t going to burn up easily like loose dirt or leaves would because those things will just blow around when a breeze comes through. That’s why gravel and sand are best for filling an uneven space like this one: they’re heavy enough to stay put but light enough for us humans (and our pets!) not feel weighed down by them during our outdoor activities like cooking dinner or playing catch with our kids before bedtime makes everyone yawns instead of having fun together as families should do every day since we live so close together anyway.

Step 3 – Lay the First Row

It’s time to build your square. The first row should be laid on their side, with each block touching the one next to it. Level the blocks to ensure they’re straight and place a mallet in between them so they don’t shift while you tap them into place with another cinder block. Fill in any gaps with mortar (also known as concrete), then use a trowel to smooth out any excess mortar that may have oozed over onto other surfaces or between the cinder blocks themselves.

Step 4 – Layer on the Cinder Blocks

Now it’s time to start building the square fire pit. If you want your square fire pit to be level, you’ll need to use cinder blocks that are exactly the same size and make sure they’re level with each other and the ground. You can use a level or just eyeball it; either way is fine.

Start by placing two cinder blocks on each side of one corner of your square box. When you set them down, make sure that both sides are flat against the ground and that there isn’t an angle at any point along their length. Once this is done, fill in where there are gaps left in between with smaller pieces of cinder block until everything feels even across every edge of your box (or however many corners have been cut).

Step 5 – Fill in Between the Cinder Blocks and Apply Mortar

Fill in between the cinder blocks and apply mortar to the surface of your square fire pit. Use a trowel to apply mortar in a way that makes the surface level and smooth it out with the trowel.

Step 6 – Smooth Out Joints and Finish Pit Interior with Gravel

In this step you will smooth out the joints and finish the interior of your pit with gravel.

  • Use a trowel to smooth out any excess mortar, then use a brush to clean up any remaining mortar that may have gotten on the sides of the cinder blocks.
  • Fill in between the cinder blocks with gravel, using as much or as little as you want depending on how large and deep you want your fire pit to be. You can place it inside or outside of your cinder block ring if desired. This is also where adding stones around it will help give it an elegant look.
  • Use a sander if necessary, but be careful not to get too aggressive here since we just filled all our nooks and crannies full of gravel…you don’t want them getting dislodged on their own accord by over-sanding. Afterward, sweep away all that excess gravel so that only 1 inch remains above ground level (or whatever height suits your needs).

Step 7 – Begin the Upper Border of Your Fire Pit

You can build the upper border using a combination of cinder blocks, mortar and concrete. First, lay down a layer of mortar. Then add a layer of cinder blocks to create an even frame. If you have gaps between your bricks, place smaller pieces in these spaces until they are filled. After filling all gaps with smaller pieces and then larger ones, add another layer of mortar over the top and smooth it out so that it looks seamless. The last step is adding some waterproofing sealant or primer before applying a coat of paint or stain to protect against any weather damage (or fireproofing).

Step 8 – Cap the Cinder Block Border with Brick or Stone

At this point, your cinder block border is complete. Now it’s time to cap the top of all four sides with brick or stone. You can do this using one of three methods:

  • Brick or Stone – You can build a concrete base around each cinder block and lay your bricks on top of it, which will give you a very sturdy border that will last for many years.
  • Concrete – You’ll need approximately 8 cubic yards (about 2 tons) of concrete per fire pit, so make sure you have access to enough before starting this step. Mix up a batch using 4 parts sand and 1 part cement; add water until it reaches the right consistency (similar to pancake batter) then pour into place over your cinder blocks forming a flat bed that fully covers them up but doesn’t go past their edges by more than 1/2 inch. Once dry, level out any bumps with sandpaper until completely smooth and let cure overnight before topping with brick or stone.

With just a few basic steps, you can build your own fire pit (and maybe even figure out how to make s’mores).

Let’s get started. Here are the materials you need:

  • Cinder blocks (about 30)
  • Mortar or concrete (around 2 bags)
  • Gravel or sand for filling in gaps between cinder blocks (a bag will be enough for this project)
  • Brick or stone to cap the border around your fire pit

Final words

And that’s all it takes to build a fire pit. Whether you’re looking for an outdoor cooking area, or just a place to sit and enjoy some time outside with friends and family, building your own fire pit is a great project that will help you create the perfect space.

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