How do stone repairs work?
From flagstone to natural stone, if it's on your porch or walkway, the mortar joints in between will crack over time. This can result in the elements getting in and under the stone, dislodging them, causing them to shift and move and even crack. To repair properly, lifting up and removing all loose mortar, then re-setting and making sure to keep the pieces level with the surrounding pieces. Also there are other options of removing the mortar entirely and installing special material designed to harden but still allow water to pass through. Since it's not mortar, it won't crack and can shift with the Earth and the stone pieces.