How To Set Capstones for a Fire Pit

Learn how to put the finishing touches on a fire pit with capstones and a seating area.

Highlights:

Step 1: Dry-Fit the Capstones
Step 2: Fill In the Gaps
Step 3: Set the Capstones
Step 4: Prepare for a Seating Area
Step 5: Dig Out the Seating Area
Step 6: Add the Finishing Touches

Step 1: Dry-Fit the Capstones

Once you’ve established your first capstone, and built up the body of the wall (Image 1) and fire brick, begin setting your capstones. In this project, experts are setting a front and back cap, so piece the capstone together so that it forms a continuous exterior and interior circle. The back cap will be placed over the fire brick, to hide it. Piecing the front and back caps together is very similar to working a puzzle, so consider dry setting your capstones all the way around before setting them in mortar. Dry-fit them so that the joint width is also consistent. The capstones should be level all the way around, so once the first cap is leveled and set, level all the other capstones off of that first stone with your four foot level (Image 2).

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- Image 2

level first capstone and set remaining capstones

Step 2: Fill In the Gaps

Before setting the caps in mortar, fill in the area between the face of the wall and the fire brick with loose stone and mortar so that there are no gaps to weaken the strength of the fire pit. Putting leftover pieces of stone in the back adds strength and helps in cleanup.

fill space between wall and brick with fine stone

Step 3: Set the Capstones

Once you’ve built the body of the fire pit and dry set the capstones, set the capstones with mortar (Image 1). Check for level once again and begin jointing. Begin by smoothing joints between stones with your jointer and follow with your paintbrush to remove any excess mortar from the stones (Image 2).

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- Image 2

smooth the joints between stones with a jointer

set capstones once body of firepit is built

Step 4: Prepare for a Seating Area

Spray out the size of your sitting area. Cut a piece of string to the desired width of the sitting area. If a sitting area is four feet wide, the string is 6.5 long (4 foot diameter of sitting area 2.5 feet radius of fire pit). Attach the string to the rebar at the center of the fire pit and spray out the sitting area with the line paint.

Step 5: Dig Out the Seating Area

Dig out the sitting area to a depth of 2-3 inches (Image 1). Cut the landscape mesh to fit using a utility knife. Placing landscape mesh underneath your crushed stone will prevent weeds from growing up between the crushed stone (Image 2). Secure the ends of the fabric with crushed stone to prevent them from curling up. Spread your crushed stone on top of the landscape fabric with your iron rake.

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- Image 2

circular sitting area is dug out around firepit

landscaping mesh under gravel prevents weed growth

Step 6: Add the Finishing Touches

Spray paint the fire brick on the inside of the fire pit with black stove paint so the focus of the fire pit is on the outside stone work not the sooty inside (Image 1). Hold a piece of cardboard against the stone work when spraying to protect the stone from the paint. Place 2-1/2 inch river rock in the base of the fire pit (Image 2). This will raise the height of the fire, help with drainage, and add contrast with the outside of the stone. Rinse the stone with water to remove dust and dirt that will have collected on the stone at the quarry.