How to Build a Stone Grotto

Dig out an arched or rectangular cave in the area where you want to place the stone grotto if you want the grotto in the side of a hill. Measure one large flat stone that you want to use as the floor of the grotto and dig out a trench of this size to approximately half the depth of the stone inside the cave. If you want to situate the stone grotto on top of the ground, dig just the trench for the floor stone of the grotto.

Place the flat stone into the space you made for the grotto floor so that it sits half-submerged in the ground. If creating a grotto on the surface of the ground, make a second trench around the perimeter of the stone floor to the width that you want to make the grotto walls, such as 12 or 18 inches, and roughly six inches deep. Use a curved or rectangular shape when digging the trench, depending on the shape that you want the grotto.

Pour coarse sand into the trench that you made around the grotto floor and tamp the sand down. Continue filling the trench until the sand fills the trench to approximately three inches.

Place flat or block-shaped stones in the approximate width that you want to make the grotto walls around the edges of the stone floor. Set the stones directly against each other and fill in the spaces in the trench with more coarse sand.

Place more flat stone or block stones on top of the first row to build the grotto walls straight up. Choose heavy stones and don’t build the grotto higher than two feet tall to prevent the need for mortar. Fill in spaces in a curved grotto design with smaller stone to create a rounded interior to the grotto.

Build the walls of the grotto to the same height. Place a flat stone large enough to reach between the grotto walls on top of the walls to create the grotto ceiling.