How to Make a Cinder Block Fire Pit

Whether it’s used as a cozy conversation area in winter or a grill space in summer, a fire pit is a practical addition to your garden. You have many options for the fire pit’s construction material, but cinder blocks are less expensive than bricks or flagstones, and they are simple to use. Build either a temporary or permanent fire pit in one of several shapes.

Choose a Location Carefully

Because you’re planning to have flames in the fire pit, select a spot for it that won’t require the fire department’s intervention. Choose a base that is non-flammable, such as bare ground or a concrete pad. Place the fire pit at least 20 feet from all structures, including your house, garage and storage or potting sheds. Clear all overhanging tree branches, or move your fire pit's location so nothing that can burn -- including low-hanging utility lines -- will hang over it.

Prepare the Site

1. Clear a circular area where you will construct your fire pit.

2. Mark the circular fire pit area, giving it an interior diameter of 3 to 4 feet if four people will sit around the pit. Add 1 foot of diameter for each additional person. Because larger cinder block circles are progressively less stable, a 4-foot diameter is the ideal size.

Tip

If you prefer a square fire pit, then follow the same rule of thumb: a fire pit that is about 3 to 4 feet across for four people.

3. 
   Remove about 6 inches of soil from inside the marked area. The first row of cinder blocks will be below ground level to add steadiness to the structure.

Warning

Contact your utility companies before you dig so their representatives can mark the locations of buried cables. In some communities, you may be able to call 811 to arrange to have the utility locations marked.

4. Add 3 inches of gravel to the bottom of the fire pit. Gravel helps with drainage.

Build the Fire Pit

Now you’re ready to stack the cinder blocks. When making a temporary fire pit, that’s all you need to do. Building a permanent pit requires one more step.

Set the first layer of cinder blocks around the circle, placing them so that their interior corners touch. The holes in the blocks should face upward. For a square fire pit, place the cinder blocks side by side instead.

Place a second layer of cinder blocks on top of the first layer, spanning the spaces between the blocks in the first row. About every 3 feet, turn one of the blocks at a slight angle to make an opening for air to get into the pit.

To make your fire pit permanent, lift the top row, one cinder block at a time, and apply an S-shaped line of masonry adhesive to the top of the first layer before replacing the lifted block. Allow the adhesive to cure according to its manufacturer’s instructions before building your first fire in the pit.

For a polished, finished appearance, add cinder block top caps atop the second row of blocks, using the masonry adhesive to make their addition permanent.