How to Make a Cultured Stone Outdoor Fireplace

Contact your city or county fire department to determine if a permit is required to build an outdoor fireplace. Locate your outdoor fireplace in an area away from buildings or overhanging trees.

Draw out a sketch of your fireplace design. Determine the size of the firebox and if you are installing a fireplace insert. Determine the source of fuel for your fireplace. You may decide to burn wood or install a natural gas or propane burning insert.

Shop for cultured stone online or from your local home improvement or building supply center. Cultured stone is available in a wide variety of colors and sizes. With a rough sketch of your project, you can determine the amount of cultured stone you will need to build your fireplace. Assemble the tools and supplies you will need for your fireplace project.

Mark out the location of your outdoor fireplace on the ground with spray paint then dig a trench that is 12 to 18 inches in width and 12 inches deep for the foundation. Compact the soil inside the trench with a hand tamper. Prepare concrete in a wheelbarrow, following the manufacturer’s instructions. Mix the cement and pour it into the trench. Smooth and level the concrete with a carpenter’s level and a masonry trowel. Allow the concrete to cure for at least 24 hours before proceeding.

Construct the fireplace with concrete blocks and mortar. Mix the mortar, following the manufacturer's directions. Spread a 1- to 2-inch layer of mortar on top of the foundation then begin placing the concrete blocks. As you lay each concrete block, check for level and adjust by using more or less mortar. After you have constructed the fireplace frame, wait for the mortar to dry for 24 to 36 hours before applying the cultured stone surround.

Mix up a small batch of mortar then spread it on the exterior surface of the cement blocks, starting at the foundation. The mortar should be 1 to 2 inches in thickness and evenly spread. Work small areas at a time. Press the cultured stone into the mortar, starting at the bottom and working around the fireplace and upward. Select the largest stones to use around the base, fitting them together like a jigsaw puzzle. Continue placing stones until there is no space left between them.

Allow the mortar to dry before installing a metal chimney cap. Some chimney caps will "snap" into place while others may need to be attached with an anchoring bolt. A chimney cap will keep rain and debris out of the chimney and help arrest any sparks that may exit the chimney.